The product labeling information includes all published material associated to a drug. Product labeling documents include information like generic names, active ingredients, ingredient strength dosage, routes of administration, appearance, usage, warnings, inactive ingredients, etc.
Gabapentin tablets, USP are white colored film coated, modified capsule shaped biconvex tablets containing 600 mg and 800 mg of gabapentin, USP.Each tablet for oral administration contains the following inactive ingredients: Mannitol, Hydroxypropyl Cellulose, Crospovidone, Talc, Magnesium Stearate and Aquarius® BP18114 Cool Vanilla.Gabapentin is described as 1-(aminomethyl)cyclohexaneacetic acid with a molecular formula of C9H17NO2 and a molecular weight of 171.24. The structural formula of gabapentin is:Gabapentin is a white to off-white crystalline solid with a pKa1 of 3.7 and a pKa2 of 10.7. It is freely soluble in water and both basic and acidic aqueous solutions. The log of the partition coefficient (n-octanol/0.05M phosphate buffer) at pH 7.4 is -1.25.This product(Gabapentin Tablets, USP 600 mg and 800 mg) meets the USP Dissolution Test 1.
Mechanism Of Action
The mechanism by which gabapentin exerts its analgesic action is unknown, but in animal models of analgesia, gabapentin prevents allodynia (pain-related behavior in response to a normally innocuous stimulus) and hyperalgesia (exaggerated response to painful stimuli). In particular, gabapentin prevents pain-related responses in several models of neuropathic pain in rats or mice (e.g., spinal nerve ligation models, streptozocin-induced diabetes model, spinal cord injury model, acute herpes zoster infection model). Gabapentin also decreases pain-related responses after peripheral inflammation (carrageenan footpad test, late phase of formalin test). Gabapentin did not alter immediate pain-related behaviors (rat tail flick test, formalin footpad acute phase, acetic acid abdominal constriction test, footpad heat irradiation test). The relevance of these models to human pain is not known.The mechanism by which gabapentin exerts its anticonvulsant action is unknown, but in animal test systems designed to detect anticonvulsant activity, gabapentin prevents seizures as do other marketed anticonvulsants. Gabapentin exhibits antiseizure activity in mice and rats in both the maximal electroshock and pentylenetetrazole seizure models and other preclinical models (e.g., strains with genetic epilepsy, etc.). The relevance of these models to human epilepsy is not known.Gabapentin is structurally related to the neurotransmitter GABA (gamma-aminobutyric acid) but it does not modify GABAA or GABAB radioligand binding, it is not converted metabolically into GABA or a GABA agonist, and it is not an inhibitor of GABA uptake or degradation. Gabapentin was tested in radioligand binding assays at concentrations up to 100 µM and did not exhibit affinity for a number of other common receptor sites, including benzodiazepine, glutamate, N-methyl-D-aspartate (NMDA), quisqualate, kainate, strychnine-insensitive or strychnine-sensitive glycine, alpha 1, alpha 2, or beta adrenergic, adenosine A1 or A2, cholinergic muscarinic or nicotinic, dopamine D1 or D2, histamine H1, serotonin S1 or S2, opiate mu, delta or kappa, cannabinoid 1, voltage-sensitive calcium channel sites labeled with nitrendipine or diltiazem, or at voltage-sensitive sodium channel sites labeled with batrachotoxinin A 20-alpha-benzoate. Furthermore, gabapentin did not alter the cellular uptake of dopamine, noradrenaline, or serotonin.In vitro studies with radiolabeled gabapentin have revealed a gabapentin binding site in areas of rat brain including neocortex and hippocampus. A high-affinity binding protein in animal brain tissue has been identified as an auxiliary subunit of voltage-activated calcium channels. However, functional correlates of gabapentin binding, if any, remain to be elucidated.
Pharmacokinetics And Drug Metabolism
All pharmacological actions following gabapentin administration are due to the activity of the parent compound; gabapentin is not appreciably metabolized in humans.
Indications & Usage
- Gabapentin Tablets, USPRead the Medication Guide before you start taking gabapentin and each time you get a refill. There may be new information. This information does not take the place of talking to your healthcare provider about your medical condition or treatment.What is the most important information I should know about gabapentin?Do not stop taking gabapentin without first talking to your healthcare provider.Stopping gabapentin suddenly can cause serious problems.Gabapentin can cause serious side effects including:1. Like other antiepileptic drugs, gabapentin may cause suicidal thoughts or actions in a very small number of people, about 1 in 500.Call a healthcare provider right away if you have any of these symptoms, especially if they are new, worse, or worry you:thoughts about suicide or dying attempts to commit suicide new or worse depressionnew or worse anxietyfeeling agitated or restlesspanic attackstrouble sleeping (insomnia)new or worse irritabilityacting aggressive, being angry, or violentacting on dangerous impulsesan extreme increase in activity and talking (mania)other unusual changes in behavior or moodHow can I watch for early symptoms of suicidal thoughts and actions?Pay attention to any changes, especially sudden changes, in mood, behaviors, thoughts, or feelings.Keep all follow-up visits with your healthcare provider as scheduled.Call your healthcare provider between visits as needed, especially if you are worried about symptoms.Do not stop taking gabapentin without first talking to a healthcare provider.Stopping gabapentin suddenly can cause serious problems. Stopping a seizure medicine suddenly in a patient who has epilepsy can cause seizures that will not stop (status epilepticus).Suicidal thoughts or actions can be caused by things other than medicines. If you have suicidal thoughts or actions, your healthcare provider may check for other causes.2. Changes in behavior and thinking - Using gabapentin in children 3 to 12 years of age can cause emotional changes, aggressive behavior, problems with concentration, restlessness, changes in school performance, and hyperactivity.What is gabapentin?Gabapentin is a prescription medicine used to treat:Pain from damaged nerves (postherpetic pain) that follows healing of shingles (a painful rash that comes after a herpes zoster infection) in adults.Partial seizures when taken together with other medicines in adults and children 3 years of age and older.Who should not take gabapentin?Do not take gabapentin if you are allergic to gabapentin or any of the other ingredients in gabapentin. See the end of this Medication Guide for a complete list of ingredients in gabapentin.What should I tell my healthcare provider before taking gabapentin?Before taking gabapentin, tell your healthcare provider if you:have or have had kidney problems or are on hemodialysishave or have had depression, mood problems, or suicidal thoughts or behaviorare pregnant or plan to become pregnant. It is not known if gabapentin can harm your unborn baby. Tell your healthcare provider right away if you become pregnant while taking gabapentin. You and your healthcare provider will decide if you should take gabapentin while you are pregnant.If you become pregnant while taking gabapentin, talk to your healthcare provider about registering with the North American Antiepileptic Drug (NAAED) Pregnancy Registry. The purpose of this registry is to collect information about the safety of antiepileptic drugs during pregnancy. You can enroll in this registry by calling 1-888-233-2334.are breastfeeding or plan to breastfeed. Gabapentin can pass into breast milk. You and your healthcare provider should decide how you will feed your baby while you take gabapentin.Tell your healthcare provider about all the medicines you take, including prescription and non-prescription medicines, vitamins, and herbal supplements.Taking gabapentin with certain other medicines can cause side effects or affect how well they work. Do not start or stop other medicines without talking to your healthcare provider.Know the medicines you take. Keep a list of them and show it to your healthcare provider and pharmacist when you get a new medicine.How should I take gabapentin?Take gabapentin exactly as prescribed. Your healthcare provider will tell you how much gabapentin to take.Do not change your dose of gabapentin without talking to your healthcare provider. If you break a tablet in half the unused half of the tablet should be taken at your next scheduled dose. Half tablets not used within several days of breaking should be thrown away.Gabapentin can be taken with or without food. If you take an antacid containing aluminum and magnesium, such as Maalox®, Mylanta®, Gelusil®, Gaviscon®, or Di-Gel®, you should wait at least 2 hours before taking your next dose of gabapentin.If you take too much gabapentin, call your healthcare provider or your local Poison Control Center right away.What should I avoid while taking gabapentin?Do not drink alcohol or take other medicines that make you sleepy or dizzy while taking gabapentin without first talking with your healthcare provider. Taking gabapentin with alcohol or drugs that cause sleepiness or dizziness may make your sleepiness or dizziness worse.Do not drive, operate heavy machinery, or do other dangerous activities until you know how gabapentin affects you. Gabapentin can slow your thinking and motor skills.What are the possible side effects of gabapentin?See "What is the most important information I should know about gabapentin?"The most common side effects of gabapentin include:dizzinesslack of coordinationviral infectionfeeling drowsyfeeling tiredfeverjerky movementsdifficulty with speakingtemporary loss of memory (amnesia)tremordifficulty with coordinationdouble visionunusual eye movementTell your healthcare provider if you have any side effect that bothers you or that does not go away.These are not all the possible side effects of gabapentin. For more information, ask your healthcare provider or pharmacist.Call your doctor for medical advice about side effects. You may report side effects to FDA at 1-800-FDA-1088.How should I store gabapentin?Store gabapentin tablets at 20° to 25°C (68° to 77°F). [See USP controlled room temperature].Keep gabapentin and all medicines out of the reach of children.General information about the safe and effective use of gabapentinMedicines are sometimes prescribed for purposes other than those listed in a Medication Guide. Do not use gabapentin for a condition for which it was not prescribed. Do not give gabapentin to other people, even if they have the same symptoms that you have. It may harm them.This Medication Guide summarizes the most important information about gabapentin. If you would like more information, talk with your healthcare provider. You can ask your healthcare provider or pharmacist for information about gabapentin that was written for healthcare professionals.For more information about gabapentin tablets, or to report side effects regarding gabapentin tablets, please call Exelan Pharmaceuticals Inc. at 1-855-295-7455.What are the ingredients in gabapentin Tablets?Active ingredient: Gabapentin, USPInactive ingredients: Mannitol, Hydroxypropyl Cellulose, Crospovidone, Talc, Magnesium Stearate and Aquarius® BP18114 Cool Vanilla.
Gabapentin tablets USP are contraindicated in patients who have demonstrated hypersensitivity to the drug or its ingredients.
Suicidal Behavior And Ideation
Antiepileptic drugs (AEDs), including gabapentin, increase the risk of suicidal thoughts or behavior in patients taking these drugs for any indication. Patients treated with any AED for any indication should be monitored for the emergence or worsening of depression, suicidal thoughts or behavior, and/or any unusual changes in mood or behavior.Pooled analyses of 199 placebo-controlled clinical trials (mono- and adjunctive therapy) of 11 different AEDs showed that patients randomized to one of the AEDs had approximately twice the risk (adjusted Relative Risk 1.8, 95% CI:1.2, 2.7) of suicidal thinking or behavior compared to patients randomized to placebo. In these trials, which had a median treatment duration of 12 weeks, the estimated incidence rate of suicidal behavior or ideation among 27,863 AED-treated patients was 0.43%, compared to 0.24% among 16,029 placebo-treated patients, representing an increase of approximately one case of suicidal thinking or behavior for every 530 patients treated. There were four suicides in drug-treated patients in the trials and none in placebo-treated patients, but the number is too small to allow any conclusion about drug effect on suicide.The increased risk of suicidal thoughts or behavior with AEDs was observed as early as one week after starting drug treatment with AEDs and persisted for the duration of treatment assessed. Because most trials included in the analysis did not extend beyond 24 weeks, the risk of suicidal thoughts or behavior beyond 24 weeks could not be assessed.The risk of suicidal thoughts or behavior was generally consistent among drugs in the data analyzed. The finding of increased risk with AEDs of varying mechanisms of action and across a range of indications suggests that the risk applies to all AEDs used for any indication. The risk did not vary substantially by age (5 to 100 years) in the clinical trials analyzed. Table 2 shows absolute and relative risk by indication for all evaluated AEDs.
TABLE 2 Risk by indication for antiepileptic drugs in the pooled analysis Indication Placebo Patients with Events Per 1000 Patients Drug Patients with Events Per 1000 Patients Relative Risk: Incidence of Events in Drug Patients/Incidence in Placebo Patients Risk Difference: Additional Drug Patients with Events Per 1000 Patients Epilepsy 1.0 3.4 3.5 2.4 Psychiatric 5.7 8.5 1.5 2.9 Other 1.0 1.8 1.9 0.9 Total 2.4 4.3 1.8 1.9The relative risk for suicidal thoughts or behavior was higher in clinical trials for epilepsy than in clinical trials for psychiatric or other conditions, but the absolute risk differences were similar for the epilepsy and psychiatric indications.Anyone considering prescribing gabapentin or any other AED must balance the risk of suicidal thoughts or behavior with the risk of untreated illness. Epilepsy and many other illnesses for which AEDs are prescribed are themselves associated with morbidity and mortality and an increased risk of suicidal thoughts and behavior. Should suicidal thoughts and behavior emerge during treatment, the prescriber needs to consider whether the emergence of these symptoms in any given patient may be related to the illness being treated.
Patients, their caregivers, and families should be informed that AEDs increase the risk of suicidal thoughts and behavior and should be advised of the need to be alert for the emergence or worsening of the signs and symptoms of depression, any unusual changes in mood or behavior, or the emergence of suicidal thoughts, behavior, or thoughts about self-harm. Behaviors of concern should be reported immediately to healthcare providers.
Neuropsychiatric Adverse Events–Pediatric Patients 3 To 12 Years Of Age
Gabapentin use in pediatric patients with epilepsy 3 to 12 years of age is associated with the occurrence of central nervous system related adverse events. The most significant of these can be classified into the following categories: 1) emotional lability (primarily behavioral problems), 2) hostility, including aggressive behaviors, 3) thought disorder, including concentration problems and change in school performance, and 4) hyperkinesia (primarily restlessness and hyperactivity). Among the gabapentin-treated patients, most of the events were mild to moderate in intensity.In controlled trials in pediatric patients 3 to 12 years of age, the incidence of these adverse events was: emotional lability 6% (gabapentin-treated patients) vs 1.3% (placebo-treated patients); hostility 5.2% vs 1.3%; hyperkinesia 4.7% vs 2.9%; and thought disorder 1.7% vs 0%. One of these events, a report of hostility, was considered serious. Discontinuation of gabapentin treatment occurred in 1.3% of patients reporting emotional lability and hyperkinesia and 0.9% of gabapentin-treated patients reporting hostility and thought disorder. One placebo-treated patient (0.4%) withdrew due to emotional lability.
Withdrawal Precipitated Seizure, Status Epilepticus
Antiepileptic drugs should not be abruptly discontinued because of the possibility of increasing seizure frequency.In the placebo-controlled studies in patients > 12 years of age, the incidence of status epilepticus in patients receiving gabapentin was 0.6% (3 of 543) versus 0.5% in patients receiving placebo (2 of 378). Among the 2074 patients > 12 years of age treated with gabapentin across all studies (controlled and uncontrolled) 31 (1.5%) had status epilepticus. Of these, 14 patients had no prior history of status epilepticus either before treatment or while on other medications. Because adequate historical data are not available, it is impossible to say whether or not treatment with gabapentin is associated with a higher or lower rate of status epilepticus than would be expected to occur in a similar population not treated with gabapentin.
In standard preclinical in vivo lifetime carcinogenicity studies, an unexpectedly high incidence of pancreatic acinar adenocarcinomas was identified in male, but not female, rats (See PRECAUTIONS , Carcinogenesis, Mutagenesis, Impairment of Fertility). The clinical significance of this finding is unknown. Clinical experience during gabapentin's premarketing development provides no direct means to assess its potential for inducing tumors in humans.
In clinical studies in adjunctive therapy in epilepsy comprising 2085 patient-years of exposure in patients > 12 years of age, new tumors were reported in 10 patients (2 breast, 3 brain, 2 lung, 1 adrenal, 1 non-Hodgkin's lymphoma, 1 endometrial carcinoma in situ), and preexisting tumors worsened in 11 patients (9 brain, 1 breast, 1 prostate) during or up to 2 years following discontinuation of gabapentin. Without knowledge of the background incidence and recurrence in a similar population not treated with gabapentin, it is impossible to know whether the incidence seen in this cohort is or is not affected by treatment.
Sudden And Unexplained Death In Patients With Epilepsy
During the course of premarketing development of gabapentin 8 sudden and unexplained deaths were recorded among a cohort of 2203 patients treated (2103 patient-years of exposure).
Some of these could represent seizure-related deaths in which the seizure was not observed, e.g., at night. This represents an incidence of 0.0038 deaths per patient-year. Although this rate exceeds that expected in a healthy population matched for age and sex, it is within the range of estimates for the incidence of sudden unexplained deaths in patients with epilepsy not receiving gabapentin (ranging from 0.0005 for the general population of epileptics to 0.003 for a clinical trial population similar to that in the gabapentin program, to 0.005 for patients with refractory epilepsy). Consequently, whether these figures are reassuring or raise further concern depends on comparability of the populations reported upon to the gabapentin cohort and the accuracy of the estimates provided.
Drug Reaction With Eosinophilia And Systemic Symptoms (Dress)/Multiorgan Hypersensitivity
Drug Reaction with Eosinophilia and Systemic Symptoms (DRESS), also known as Multiorgan hypersensitivity, has been reported in patients taking antiepileptic drugs, including gabapentin. Some of these events have been fatal or life-threatening. DRESS typically, although not exclusively, presents with fever, rash, and/or lymphadenopathy, in association with other organ system involvement, such as hepatitis, nephritis, hematological abnormalities, myocarditis, or myositis sometimes resembling an acute viral infection. Eosinophilia is often present. Because this disorder is variable in its expression, other organ systems not noted here may be involved. It is important to note that early manifestations of hypersensitivity, such as fever or lymphadenopathy, may be present even though rash is not evident. If such signs or symptoms are present, the patient should be evaluated immediately. Gabapentin should be discontinued if an alternative etiology for the signs or symptoms cannot be established.
Information For Patients
Inform patients of the availability of a Medication Guide, and instruct them to read the Medication Guide prior to taking gabapentin. Instruct patients to take gabapentin only as prescribed.Patients, their caregivers, and families should be counseled that AEDs, including gabapentin,may increase the risk of suicidal thoughts and behavior and should be advised of the need to be alert for the emergence or worsening of symptoms of depression, any unusual changes in mood or behavior, or the emergence of suicidal thoughts, behavior, or thoughts about self-harm. Behaviors of concern should be reported immediately to healthcare providers.Patients should be advised that gabapentin may cause dizziness, somnolence and other symptoms and signs of CNS depression. Accordingly, they should be advised neither to drive a car nor to operate other complex machinery until they have gained sufficient experience on gabapentin to gauge whether or not it affects their mental and/or motor performance adversely.Patients who require concomitant treatment with morphine may experience increases in gabapentin concentrations. Patients should be carefully observed for signs of CNS depression, such as somnolence, and the dose of gabapentin or morphine should be reduced appropriately (see Drug Interactions).Patients should be encouraged to enroll in the North American Antiepileptic Drug (NAAED) Pregnancy Registry if they become pregnant. This registry is collecting information about the safety of antiepileptic drugs during pregnancy. To enroll, patients can call the toll free number 1-888-233-2334 (see PRECAUTIONS, Pregnancy section).
Clinical trials data do not indicate that routine monitoring of clinical laboratory parameters is necessary for the safe use of gabapentin. The value of monitoring gabapentin blood concentrations has not been established. Gabapentin may be used in combination with other antiepileptic drugs without concern for alteration of the blood concentrations of gabapentin or of other antiepileptic drugs.
In vitro studies were conducted to investigate the potential of gabapentin to inhibit the major cytochrome P450 enzymes (CYP1A2, CYP2A6, CYP2C9, CYP2C19, CYP2D6, CYP2E1, and CYP3A4) that mediate drug and xenobiotic metabolism using isoform selective marker substrates and human liver microsomal preparations. Only at the highest concentration tested (171 mcg/mL; 1 mM) was a slight degree of inhibition (14% to 30%) of isoform CYP2A6 observed. No inhibition of any of the other isoforms tested was observed at gabapentin concentrations up to 171 mcg/mL (approximately 15 times the Cmax at 3600 mg/day).Gabapentin is not appreciably metabolized nor does it interfere with the metabolism of commonly coadministered antiepileptic drugs.The drug interaction data described in this section were obtained from studies involving healthy adults and adult patients with epilepsy.
Drug/Laboratory Test Interactions
Because false positive readings were reported with the Ames N-Multistix SG® dipstick test for urinary protein when gabapentin was added to other antiepileptic drugs, the more specific sulfosalicylic acid precipitation procedure is recommended to determine the presence of urine protein.
Carcinogenesis, Mutagenesis, Impairment Of Fertility
Gabapentin was given in the diet to mice at 200, 600, and 2000 mg/kg/day and to rats at 250, 1000, and 2000 mg/kg/day for 2 years. A statistically significant increase in the incidence of pancreatic acinar cell adenomas and carcinomas was found in male rats receiving the high dose; the no-effect dose for the occurrence of carcinomas was 1000 mg/kg/day. Peak plasma concentrations of gabapentin in rats receiving the high dose of 2000 mg/kg were 10 times higher than plasma concentrations in humans receiving 3600 mg per day, and in rats receiving 1000 mg/kg/day peak plasma concentrations were 6.5 times higher than in humans receiving 3600 mg/day. The pancreatic acinar cell carcinomas did not affect survival, did not metastasize and were not locally invasive. The relevance of this finding to carcinogenic risk in humans is unclear.Studies designed to investigate the mechanism of gabapentin-induced pancreatic carcinogenesis in rats indicate that gabapentin stimulates DNA synthesis in rat pancreatic acinar cells in vitro and, thus, may be acting as a tumor promoter by enhancing mitogenic activity. It is not known whether gabapentin has the ability to increase cell proliferation in other cell types or in other species, including humans.Gabapentin did not demonstrate mutagenic or genotoxic potential in three in vitro and four in vivo assays. It was negative in the Ames test and the in vitro HGPRT forward mutation assay in Chinese hamster lung cells; it did not produce significant increases in chromosomal aberrations in the in vitro Chinese hamster lung cell assay; it was negative in the in vivo chromosomal aberration assay and in the in vivo micronucleus test in Chinese hamster bone marrow; it was negative in the in vivo mouse micronucleus assay; and it did not induce unscheduled DNA synthesis in hepatocytes from rats given gabapentin.No adverse effects on fertility or reproduction were observed in rats at doses up to 2000 mg/kg (approximately 5 times the maximum recommended human dose on a mg/m2 basis).
Pregnancy Category C: Gabapentin has been shown to be fetotoxic in rodents, causing delayed ossification of several bones in the skull, vertebrae, forelimbs, and hindlimbs. These effects occurred when pregnant mice received oral doses of 1000 or 3000 mg/kg/day during the period of organogenesis, or approximately 1 to 4 times the maximum dose of 3600 mg/day given to epileptic patients on a mg/m2 basis. The no-effect level was 500 mg/kg/day or approximately ½ of the human dose on a mg/m2 basis.When rats were dosed prior to and during mating, and throughout gestation, pups from all dose groups (500, 1000 and 2000 mg/kg/day) were affected. These doses are equivalent to less than approximately 1 to 5 times the maximum human dose on a mg/m2 basis. There was an increased incidence of hydroureter and/or hydronephrosis in rats in a study of fertility and general reproductive performance at 2000 mg/kg/day with no effect at 1000 mg/kg/day, in a teratology study at 1500 mg/kg/day with no effect at 300 mg/kg/day, and in a perinatal and postnatal study at all doses studied (500, 1000 and 2000 mg/kg/day). The doses at which the effects occurred are approximately 1 to 5 times the maximum human dose of 3600 mg/day on a mg/m2 basis; the no-effect doses were approximately 3 times (Fertility and General Reproductive Performance study) and approximately equal to (Teratogenicity study) the maximum human dose on a mg/m2 basis. Other than hydroureter and hydronephrosis, the etiologies of which are unclear, the incidence of malformations was not increased compared to controls in offspring of mice, rats, or rabbits given doses up to 50 times (mice), 30 times (rats), and 25 times (rabbits) the human daily dose on a mg/kg basis, or 4 times (mice), 5 times (rats), or 8 times (rabbits) the human daily dose on a mg/m2 basis.In a teratology study in rabbits, an increased incidence of postimplantation fetal loss occurred in dams exposed to 60, 300, and 1500 mg/kg/day, or less than approximately 1/4 to 8 times the maximum human dose on a mg/m2 basis. There are no adequate and well-controlled studies in pregnant women. This drug should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.To provide information regarding the effects of in utero exposure to gabapentin, physicians are advised to recommend that pregnant patients taking gabapentin enroll in the North American Antiepileptic Drug (NAAED) Pregnancy Registry. This can be done by calling the toll free number 1-888-233-2334, and must be done by patients themselves. Information on the registry can also be found at the website http://www.aedpregnancyregistry.org/.
Use In Nursing Mothers
Gabapentin is secreted into human milk following oral administration. A nursed infant could be exposed to a maximum dose of approximately 1 mg/kg/day of gabapentin. Because the effect on the nursing infant is unknown, gabapentin should be used in women who are nursing only if the benefits clearly outweigh the risks.
Safety and effectiveness of gabapentin in the management of postherpetic neuralgia in pediatric patients have not been established.Effectiveness as adjunctive therapy in the treatment of partial seizures in pediatric patients below the age of 3 years has not been established (see CLINICAL PHARMACOLOGY, Clinical Studies).
The total number of patients treated with gabapentin in controlled clinical trials in patients with postherpetic neuralgia was 336, of which 102 (30%) were 65 to 74 years of age, and 168 (50%) were 75 years of age and older. There was a larger treatment effect in patients 75 years of age and older compared with younger patients who received the same dosage. Since gabapentin is almost exclusively eliminated by renal excretion, the larger treatment effect observed in patients ≥75 years may be a consequence of increased gabapentin exposure for a given dose that results from an age-related decrease in renal function. However, other factors cannot be excluded. The types and incidence of adverse events were similar across age groups except for peripheral edema and ataxia, which tended to increase in incidence with age.Clinical studies of gabapentin in epilepsy did not include sufficient numbers of subjects aged 65 and over to determine whether they responded differently from younger subjects. Other reported clinical experience has not identified differences in responses between the elderly and younger patients. In general, dose selection for an elderly patient should be cautious, usually starting at the low end of the dosing range, reflecting the greater frequency of decreased hepatic, renal, or cardiac function, and of concomitant disease or other drug therapy.This drug is known to be substantially excreted by the kidney, and the risk of toxic reactions to this drug may be greater in patients with impaired renal function. Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and dose should be adjusted based on creatinine clearance values in these patients (see CLINICAL PHARMACOLOGY, ADVERSE REACTIONS, and DOSAGE AND ADMINISTRATION sections).
Incidence In Controlled Clinical Trials
Table 3 lists treatment-emergent signs and symptoms that occurred in at least 1% of gabapentin-treated patients with postherpetic neuralgia participating in placebo-controlled trials and that were numerically more frequent in the gabapentin group than in the placebo group. Adverse events were usually mild to moderate in intensity.TABLE 3. Treatment-Emergent Adverse Event Incidence in Controlled Trials in Postherpetic Neuralgia (Events in at least 1% of Gabapentin-Treated Patients and Numerically More Frequent Than in the Placebo Group)
Body System/Preferred Term
Gabapentin N=336 %
Body as a Whole Asthenia 5.7 4.8 Infection 5.1 3.5 Headache 3.3 3.1 Accidental injury 3.3 1.3 Abdominal pain 2.7 2.6 Digestive System Diarrhea 5.7 3.1 Dry mouth 4.8 1.3 Constipation 3.9 1.8 Nausea 3.9 3.1 Vomiting 3.3 1.8 Flatulence 2.1 1.8 Metabolic and Nutritional Disorders Peripheral edema 8.3 2.2 Weight gain 1.8 0.0 Hyperglycemia 1.2 0.4 Nervous System Dizziness 28.0 7.5 Somnolence 21.4 5.3 Ataxia 3.3 0.0 Thinking abnormal 2.7 0.0 Abnormal gait 1.5 0.0 Incoordination 1.5 0.0 Amnesia 1.2 0.9 Hypesthesia 1.2 0.9 Respiratory System Pharyngitis 1.2 0.4 Skin and Appendages Rash 1.2 0.9 Special Senses
AmblyopiaReported as blurred vision 2.7 0.9 Conjunctivitis 1.2 0.0 Diplopia 1.2 0.0 Otitis media 1.2 0.0
Other events in more than 1% of patients but equally or more frequent in the placebo group included pain, tremor, neuralgia, back pain, dyspepsia, dyspnea, and flu syndrome.
There were no clinically important differences between men and women in the types and incidence of adverse events. Because there were few patients whose race was reported as other than white, there are insufficient data to support a statement regarding the distribution of adverse events by race.
Table 4 lists treatment-emergent signs and symptoms that occurred in at least 1% of gabapentin -treated patients > 12 years of age with epilepsy participating in placebo-controlled trials and were numerically more common in the gabapentin group. In these studies, either gabapentin or placebo was added to the patient's current antiepileptic drug therapy. Adverse events were usually mild to moderate in intensity.The prescriber should be aware that these figures, obtained when gabapentin was added to concurrent antiepileptic drug therapy, cannot be used to predict the frequency of adverse events in the course of usual medical practice where patient characteristics and other factors may differ from those prevailing during clinical studies. Similarly, the cited frequencies cannot be directly compared with figures obtained from other clinical investigations involving different treatments, uses, or investigators. An inspection of these frequencies, however, does provide the prescribing physician with one basis to estimate the relative contribution of drug and nondrug factors to the adverse event incidences in the population studied.TABLE 4. Treatment-Emergent Adverse Event Incidence in Controlled Add-On Trials In Patients >12 years of age (Events in at least 1% of gabapentin patients and numerically more frequent than in the placebo group)
Body System/Adverse Event
GabapentinPlus background antiepileptic drug therapyN=543 %
Body As A Whole Fatigue 11.0 5.0 Weight Increase 2.9 1.6 Back Pain 1.8 0.5 Peripheral Edema 1.7 0.5 Cardiovascular Vasodilatation 1.1 0.3 Digestive System Dyspepsia 2.2 0.5 Mouth or Throat Dry 1.7 0.5 Constipation 1.5 0.8 Dental Abnormalities 1.5 0.3 Increased Appetite 1.1 0.8 Hematologic and Lymphatic Systems Leukopenia 1.1 0.5 Musculoskeletal System Myalgia 2.0 1.9 Fracture 1.1 0.8 Nervous System Somnolence 19.3 8.7 Dizziness 17.1 6.9 Ataxia 12.5 5.6 Nystagmus 8.3 4.0 Tremor 6.8 3.2 Nervousness 2.4 1.9 Dysarthria 2.4 0.5 Amnesia 2.2 0.0 Depression 1.8 1.1 Thinking Abnormal 1.7 1.3 Twitching 1.3 0.5 Coordination Abnormal 1.1 0.3 Respiratory System Rhinitis 4.1 3.7 Pharyngitis 2.8 1.6 Coughing 1.8 1.3 Skin and Appendages Abrasion 1.3 0.0 Pruritus 1.3 0.5 Urogenital System Impotence 1.5 1.1 Special Senses Diplopia 5.9 1.9
AmblyopiaAmblyopia was often described as blurred vision. 4.2 1.1 Laboratory Deviations WBC Decreased 1.1 0.5
Other events in more than 1% of patients >12 years of age but equally or more frequent in the placebo group included: headache, viral infection, fever, nausea and/or vomiting, abdominal pain, diarrhea, convulsions, confusion, insomnia, emotional lability, rash, acne.Among the treatment-emergent adverse events occurring at an incidence of at least 10% of gabapentin-treated patients, somnolence and ataxia appeared to exhibit a positive dose-response relationship.The overall incidence of adverse events and the types of adverse events seen were similar among men and women treated with gabapentin. The incidence of adverse events increased slightly with increasing age in patients treated with either gabapentin or placebo. Because only 3% of patients (28/921) in placebo-controlled studies were identified as nonwhite (black or other), there are insufficient data to support a statement regarding the distribution of adverse events by race.Table 5 lists treatment-emergent signs and symptoms that occurred in at least 2% of gabapentin -treated patients age 3 to 12 years of age with epilepsy participating in placebo-controlled trials and were numerically more common in the gabapentin group. Adverse events were usually mild to moderate in intensity.TABLE 5. Treatment-Emergent Adverse Event Incidence in Pediatric Patients Age 3 to 12 Years in a Controlled Add-On Trial (Events in at least 2% of gabapentin patients and numerically more frequent than in the placebo group)
Body System/Adverse Event
GabapentinPlus background antiepileptic drug therapyN=119%
Body As A Whole Viral Infection 10.9 3.1 Fever 10.1 3.1 Weight Increase 3.4 0.8 Fatigue 3.4 1.6 Digestive System Nausea and/or Vomiting 8.4 7 Nervous System Somnolence 8.4 4.7 Hostility 7.6 2.3 Emotional Lability 4.2 1.6 Dizziness 2.5 1.6 Hyperkinesia 2.5 0.8 Respiratory System Bronchitis 3.4 0.8 Respiratory Infection 2.5 0.8
Other events in more than 2% of pediatric patients 3 to 12 years of age but equally or more frequent in the placebo group included: pharyngitis, upper respiratory infection, headache, rhinitis, convulsions, diarrhea, anorexia, coughing, and otitis media.
Clinical Trials In Adults And Adolescents (Except Clinical Trials In Neuropathic Pain)
Gabapentin has been administered to 4717 patients > 12 years of age during all adjunctive therapy clinical trials (except clinical trials in patients with neuropathic pain), only some of which were placebo-controlled. During these trials, all adverse events were recorded by the clinical investigators using terminology of their own choosing. To provide a meaningful estimate of the proportion of individuals having adverse events, similar types of events were grouped into a smaller number of standardized categories using modified COSTART dictionary terminology. These categories are used in the listing below. The frequencies presented represent the proportion of the 4717 patients > 12 years of age exposed to gabapentin who experienced an event of the type cited on at least one occasion while receiving gabapentin. All reported events are included except those already listed in Table 4, those too general to be informative, and those not reasonably associated with the use of the drug.Events are further classified within body system categories and enumerated in order of decreasing frequency using the following definitions: frequent adverse events are defined as those occurring in at least 1/100 patients; infrequent adverse events are those occurring in 1/100 to 1/1000 patients; rare events are those occurring in fewer than 1/1000 patients.Body As A Whole: Frequent: asthenia, malaise, face edema.Infrequent: allergy, generalized edema, weight decrease, chill.Rare: strange feelings, lassitude, alcohol intolerance, hangover effect.Cardiovascular System: Frequent: hypertension.Infrequent: hypotension, angina pectoris, peripheral vascular disorder, palpitation, tachycardia, migraine, murmur.Rare: atrial fibrillation, heart failure, thrombophlebitis, deep thrombophlebitis, myocardial infarction, cerebrovascular accident, pulmonary thrombosis, ventricular extrasystoles, bradycardia, premature atrial contraction, pericardial rub, heart block, pulmonary embolus, hyperlipidemia, hypercholesterolemia, pericardial effusion, pericarditis.Digestive System: Frequent: anorexia, flatulence, gingivitis.Infrequent: glossitis, gum hemorrhage, thirst, stomatitis, increased salivation, gastroenteritis, hemorrhoids, bloody stools, fecal incontinence, hepatomegaly.Rare: dysphagia, eructation, pancreatitis, peptic ulcer, colitis, blisters in mouth, tooth discolor, perlèche, salivary gland enlarged, lip hemorrhage, esophagitis, hiatal hernia, hematemesis, proctitis, irritable bowel syndrome, rectal hemorrhage, esophageal spasm.Endocrine System:Rare: hyperthyroid, hypothyroid, goiter, hypoestrogen, ovarian failure, epididymitis, swollen testicle, cushingoid appearance.
Hematologic and Lymphatic System:Frequent: purpura most often described as bruises resulting from physical trauma.Infrequent: anemia, thrombocytopenia, lymphadenopathy.Rare: WBC count increased, lymphocytosis, non-Hodgkin’s lymphoma, bleeding time increased.Musculoskeletal System: Frequent: arthralgia.Infrequent: tendinitis, arthritis, joint stiffness, joint swelling, positive Romberg test.Rare: costochondritis, osteoporosis, bursitis, contracture.
Nervous System:Frequent: vertigo, hyperkinesia, paresthesia, decreased or absent reflexes, increased reflexes, anxiety, hostility.Infrequent: CNS tumors, syncope, dreaming abnormal, aphasia, hypesthesia, intracranial hemorrhage, hypotonia, dysesthesia, paresis, dystonia, hemiplegia, facial paralysis, stupor, cerebellar dysfunction, positive Babinski sign, decreased position sense, subdural hematoma, apathy, hallucination, decrease or loss of libido, agitation, paranoia, depersonalization, euphoria, feeling high, doped-up sensation, psychosis.Rare: choreoathetosis, orofacial dyskinesia, encephalopathy, nerve palsy, personality disorder, increased libido, subdued temperament, apraxia, fine motor control disorder, meningismus, local myoclonus, hyperesthesia, hypokinesia, mania, neurosis, hysteria, antisocial reaction.
Respiratory System:Frequent: pneumonia.Infrequent: epistaxis, dyspnea, apnea.Rare: mucositis, aspiration pneumonia, hyperventilation, hiccup, laryngitis, nasal obstruction, snoring, bronchospasm, hypoventilation, lung edema.
Dermatological:Infrequent: alopecia, eczema, dry skin, increased sweating, urticaria, hirsutism, seborrhea, cyst, herpes simplex.
Rare: herpes zoster, skin discolor, skin papules, photosensitive reaction, leg ulcer, scalp seborrhea, psoriasis, desquamation, maceration, skin nodules, subcutaneous nodule, melanosis, skin necrosis, local swelling.Urogenital System:Infrequent: hematuria, dysuria, urination frequency, cystitis, urinary retention, urinary incontinence, vaginal hemorrhage, amenorrhea, dysmenorrhea, menorrhagia, breast cancer, unable to climax, ejaculation abnormal.Rare: kidney pain, leukorrhea, pruritus genital, renal stone, acute renal failure, anuria, glycosuria, nephrosis, nocturia, pyuria, urination urgency, vaginal pain, breast pain, testicle pain.Special Senses:Frequent: abnormal vision.Infrequent: cataract, conjunctivitis, eyes dry, eye pain, visual field defect, photophobia, bilateral or unilateral ptosis, eye hemorrhage, hordeolum, hearing loss, earache, tinnitus, inner ear infection, otitis, taste loss, unusual taste, eye twitching, ear fullness.Rare: eye itching, abnormal accommodation, perforated ear drum, sensitivity to noise, eye focusing problem, watery eyes, retinopathy, glaucoma, iritis, corneal disorders, lacrimal dysfunction, degenerative eye changes, blindness, retinal degeneration, miosis, chorioretinitis, strabismus, eustachian tube dysfunction, labyrinthitis, otitis externa, odd smell.
Clinical Trials In Pediatric Patients With Epilepsy
Adverse events occurring during epilepsy clinical trials in 449 pediatric patients 3 to 12 years of age treated with gabapentin that were not reported in adjunctive trials in adults are:Body as a Whole: dehydration, infectious mononucleosis
Digestive System: hepatitis
Hemic and Lymphatic System: coagulation defect
Nervous System: aura disappeared, occipital neuralgia
Psychobiologic Function: sleepwalking
Respiratory System: pseudocroup, hoarseness
Clinical Trials In Adults With Neuropathic Pain Of Various Etiologies
Safety information was obtained in 1173 patients during double-blind and open-label clinical trials including neuropathic pain conditions for which efficacy has not been demonstrated. Adverse events reported by investigators were grouped into standardized categories using modified COSTART IV terminology. Listed below are all reported events except those already listed in Table 3 and those not reasonably associated with the use of the drug.
Events are further classified within body system categories and enumerated in order of decreasing frequency using the following definitions: frequent adverse events are defined as those occurring in at least 1/100 patients; infrequent adverse events are those occurring in 1/100 to 1/1000 patients; rare events are those occurring in fewer than 1/1000 patients.Body as a Whole:Infrequent: chest pain, cellulitis, malaise, neck pain, face edema, allergic reaction, abscess, chills, chills and fever, mucous membrane disorderRare: body odor, cyst, fever, hernia, abnormal BUN value, lump in neck, pelvic pain, sepsis, viral infectionCardiovascular System:Infrequent: hypertension, syncope, palpitation, migraine, hypotension, peripheral vascular disorder, cardiovascular disorder, cerebrovascular accident, congestive heart failure, myocardial infarction, vasodilatationRare: angina pectoris, heart failure, increased capillary fragility, phlebitis, thrombophlebitis, varicose veinDigestive System:Infrequent: gastroenteritis, increased appetite, gastrointestinal disorder, oral moniliasis, gastritis, tongue disorder, thirst, tooth disorder, abnormal stools, anorexia, liver function tests abnormal, periodontal abscessRare: cholecystitis, cholelithiasis, duodenal ulcer, fecal incontinence, gamma glutamyl transpeptidase increased, gingivitis, intestinal obstruction, intestinal ulcer, melena, mouth ulceration, rectal disorder, rectal hemorrhage, stomatitisEndocrine System:Infrequent: diabetes mellitus
Hemic and Lymphatic System:Infrequent: ecchymosis, anemiaRare: lymphadenopathy, lymphoma-like reaction, prothrombin decreasedMetabolic and Nutritional:Infrequent: edema, gout, hypoglycemia, weight lossRare: alkaline phosphatase increased, diabetic ketoacidosis, lactic dehydrogenase increasedMusculoskeletal:Infrequent: arthritis, arthralgia, myalgia, arthrosis, leg cramps, myastheniaRare: shin bone pain, joint disorder, tendon disorderNervous System:Frequent: confusion, depressionInfrequent: vertigo, nervousness, paresthesia, insomnia, neuropathy, libido decreased, anxiety, depersonalization, reflexes decreased, speech disorder, abnormal dreams, dysarthria, emotional lability, nystagmus, stupor, circumoral paresthesia, euphoria, hyperesthesia, hypokinesiaRare: agitation, hypertonia, libido increased, movement disorder, myoclonus, vestibular disorderRespiratory System:Infrequent: cough increased, bronchitis, rhinitis, sinusitis, pneumonia, asthma, lung disorder, epistaxisRare: hemoptysis, voice alterationSkin and Appendages:Infrequent: pruritus, skin ulcer, dry skin, herpes zoster, skin disorder, fungal dermatitis, furunculosis, herpes simplex, psoriasis, sweating, urticaria, vesiculobullous rashRare: acne, hair disorder, maculopapular rash, nail disorder, skin carcinoma, skin discoloration, skin hypertrophySpecial Senses:Infrequent: abnormal vision, ear pain, eye disorder, taste perversion, deafnessRare: conjunctival hyperemia, diabetic retinopathy, eye pain, fundi with microhemorrhage, retinal vein thrombosis, taste loss Urogenital System:Infrequent: urinary tract infection, dysuria, impotence, urinary incontinence, vaginal moniliasis, breast pain, menstrual disorder, polyuria, urinary retentionRare: cystitis, ejaculation abnormal, swollen penis, gynecomastia, nocturia, pyelonephritis, swollen scrotum, urinary frequency, urinary urgency, urine abnormality
Postmarketing And Other Experience
In addition to the adverse experiences reported during clinical testing of gabapentin, the following adverse experiences have been reported in patients receiving marketed gabapentin. These adverse experiences have not been listed above and data are insufficient to support an estimate of their incidence or to establish causation. The listing is alphabetized: angioedema, blood glucose fluctuation, breast hypertrophy, erythema multiforme, elevated liver function tests, fever, hyponatremia, jaundice, movement disorder, Stevens-Johnson syndrome.Adverse events following the abrupt discontinuation of gabapentin have also been reported. The most frequently reported events were anxiety, insomnia, nausea, pain and sweating.
Drug Abuse And Dependence
The abuse and dependence potential of gabapentin has not been evaluated in human studies.
A lethal dose of gabapentin was not identified in mice and rats receiving single oral doses as high as 8000 mg/kg. Signs of acute toxicity in animals included ataxia, labored breathing, ptosis, sedation, hypoactivity, or excitation.Acute oral overdoses of gabapentin up to 49 grams have been reported. In these cases, double vision, slurred speech, drowsiness, lethargy and diarrhea were observed. All patients recovered with supportive care.Gabapentin can be removed by hemodialysis. Although hemodialysis has not been performed in the few overdose cases reported, it may be indicated by the patient’s clinical state or in patients with significant renal impairment.
Dosage & Administration
Gabapentin tablets USP are given orally with or without food. Patients should be informed that, should they break the scored 600 or 800 mg tablet in order to administer a half-tablet, they should take the unused half-tablet as the next dose. Half-tablets not used within several days of breaking the scored tablet should be discarded.If gabapentin tablets USP dose is reduced, discontinued or substituted with an alternative medication, this should be done gradually over a minimum of 1 week (a longer time period may be needed at the discretion of the prescriber).
Dosage In Renal Impairment
Creatinine clearance is difficult to measure in outpatients. In patients with stable renal function, creatinine clearance (CCr) can be reasonably well estimated using the equation of Cockcroft and Gault:
for females CCr =(0.85)(140-age)(weight)/[(72)(SCr)]for males CCr =(140-age)(weight)/[(72)(SCr)]
where age is in years, weight is in kilograms and SCr is serum creatinine in mg/dL.
Dosage adjustment in patients ≥12 years of age with compromised renal function or undergoing hemodialysis is recommended as follows (see dosing recommendations above for effective doses in each indication).TABLE 6. Gabapentin Dosage Based on Renal Function
Renal Function Creatinine Clearance (mL/min)
Total Daily Dose Range (mg/day)
≥60 900 to 3600 300 TID 400 TID 600 TID 800 TID 1200 TID >30 to 59 400 to 1400 200 BID 300 BID 400 BID 500 BID 700 BID >15 to 29 200 to 700 200 QD 300 QD 400 QD 500 QD 700 QD
15For patients with creatinine clearance <15 mL/min, reduce daily dose in proportion to creatinine clearance (e.g., patients with a creatinine clearance of 7.5 mL/min should receive one-half the daily dose that patients with a creatinine clearance of 15 mL/min receive). 100 to 300 100 QD 125 QD 150 QD 200 QD 300 QD
Post-Hemodialysis Supplemental Dose (mg)Patients on hemodialysis should receive maintenance doses based on estimates of creatinine clearance as indicated in the upper portion of the table and a supplemental post-hemodialysis dose administered after each 4 hours of hemodialysis as indicated in the lower portion of the table. Hemodialysis
The use of gabapentin tablets USP in patients <12 years of age with compromised renal function has not been studied.
Dosage In Elderly
Because elderly patients are more likely to have decreased renal function, care should be taken in dose selection, and dose should be adjusted based on creatinine clearance values in these patients.
Gabapentin Tablets, USP 600 mg: White colored film coated, Modified Capsule shaped, biconvex tablets de-bossed with '1' on the left side of the bisect and '2' on the right side of the bisect on one side and bisect on other; supplied in:30 TABLET in a BOTTLE (0440-5562-30)60 TABLET in a BOTTLE (0440-5562-60)300 TABLET in a BOTTLE (0440-5562-81)120 TABLET in a BOTTLE (0440-5562-91)180 TABLET in a BOTTLE (0440-5562-92)270 TABLET in a BOTTLE (0440-5562-94)500 TABLET in a BOTTLE (0440-5562-05)90 TABLET in a BOTTLE (0440-5562-90)Gabapentin Tablets, USP 800 mg: White colored film coated, Modified Capsule shaped, biconvex tablets de-bossed with '1' on the left side of the bisect and '3' on the right side of the bisect on one side and bisect on other; supplied in:30 TABLET in a BOTTLE (0440-5563-30)60 TABLET in a BOTTLE (0440-5563-60)300 TABLET in a BOTTLE (0440-5563-81)120 TABLET in a BOTTLE (0440-5563-91)180 TABLET in a BOTTLE (0440-5563-92)270 TABLET in a BOTTLE (0440-5563-94)500 TABLET in a BOTTLE (0440-5563-05)90 TABLET in a BOTTLE (0440-5563-90)Store at 20° to 25°C (68° to 77°F). [See USP controlled room temperature].PACKAGED BY: AIDAREX PHARMACEUTICALS LLC, CORONA CA, 92880 Rev: 08/2016.
* Please review the disclaimer below.