General
Before initiating therapy, a detailed history and physical
examination should be made.
Carbamazepine should be used with caution in patients with a mixed seizure
disorder that includes atypical absence seizures, since in these patients
carbamazepine has been associated with increased frequency of generalized
convulsions (see INDICATIONS AND USAGE).
Therapy should be prescribed only after critical benefit-to-risk appraisal in
patients with a history of cardiac conduction disturbance, including second and
third degree AV heart block; cardiac, hepatic, or renal damage; adverse
hematologic or hypersensitivity reaction to other drugs, including reactions to
other anticonvulsants; or interrupted courses of therapy with carbamazepine.
AV heart block, including second and third degree block, have been reported
following carbamazepine treatment. This occurred generally, but not solely, in
patients with underlying EKG abnormalities or risk factors for conduction
disturbances.
Hepatic effects, ranging from slight elevations in liver enzymes to rare
cases of hepatic failure have been reported (see ADVERSE
REACTIONS and PRECAUTIONS, LaboratoryTests). In some cases,
hepatic effects may progress despite discontinuation of the drug.
Multiorgan hypersensitivity reactions occurring days to weeks or months after
initiating treatment have been reported in rare cases (see ADVERSE REACTIONS, Other and PRECAUTIONS, Information for Patients).
Discontinuation of carbamazepine should be considered if any evidence of
hypersensitivity develops.
Hypersensitivity reactions to carbamazepine have been reported in patients
who previously experienced this reaction to anticonvulsants including phenytoin
and phenobarbital. A history of hypersensitivity reactions should be obtained
for a patient and the immediate family members. If positive, caution should be
used in prescribing carbamazepine.
Information for Patients
Patients should be made aware of the early toxic signs and
symptoms of a potential hematologic problem, as well as dermatologic,
hypersensitivity or hepatic reactions. These symptoms may include, but are not
limited to, fever, sore throat, rash, ulcers in the mouth, easy bruising,
lymphadenopathy and petechial or purpuric hemorrhage, and in the case of liver
reactions, anorexia, nausea/vomiting, or jaundice. The patient should be advised
that, because these signs and symptoms may signal a serious reaction, that they
must report any occurrence immediately to a physician. In addition, the patient
should be advised that these signs and symptoms should be reported even if mild
or when occurring after extended use.
Patients, their caregivers, and families should be counseled that AEDs,
including carbamazepine, 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.
Carbamazepine may interact with some drugs. Therefore, patients should be
advised to report to their doctors the use of any other prescription or
nonprescription medications or herbal products.
Caution should be exercised if alcohol is taken in combination with
carbamazepine therapy, due to a possible additive sedative effect.
Since dizziness and drowsiness may occur, patients should be cautioned about
the hazards of operating machinery or automobiles or engaging in other
potentially dangerous tasks.
Patients should be encouraged to enroll in the 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 WARNINGS, Usage in Pregnancy).
Laboratory Tests
For genetically at-risk patients (see WARNINGS), high-resolution ‘HLA-B*1502 typing’ is recommended. The test is positive if
either one or two HLA-B*1502 alleles are detected and
negative if no HLA-B*1502 alleles are detected.
Complete pretreatment blood counts, including platelets and possibly
reticulocytes and serum iron, should be obtained as a baseline. If a patient in
the course of treatment exhibits low or decreased white blood cell or platelet
counts, the patient should be monitored closely. Discontinuation of the drug
should be considered if any evidence of significant bone marrow depression
develops.
Baseline and periodic evaluations of liver function, particularly in patients
with a history of liver disease, must be performed during treatment with this
drug since liver damage may occur (see PRECAUTIONS,
General and ADVERSE REACTIONS).
Carbamazepine should be discontinued, based on clinical judgment, if indicated
by newly occurring or worsening clinical or laboratory evidence of liver
dysfunction or hepatic damage, or in the case of active liver disease.
Baseline and periodic eye examinations, including slit-lamp, funduscopy, and
tonometry, are recommended since many phenothiazines and related drugs have been
shown to cause eye changes.
Baseline and periodic complete urinalysis and BUN determinations are
recommended for patients treated with this agent because of observed renal
dysfunction.
Monitoring of blood levels (see CLINICAL
PHARMACOLOGY) has increased the efficacy and safety of anticonvulsants.
This monitoring may be particularly useful in cases of dramatic increase in
seizure frequency and for verification of compliance. In addition, measurement
of drug serum levels may aid in determining the cause of toxicity when more than
one medication is being used.
Thyroid function tests have been reported to show decreased values with
carbamazepine administered alone.
Hyponatremia has been reported in association with carbamazepine use, either
alone or in combination with other drugs.
Interference with some pregnancy tests has been reported.
Drug Interactions
Clinically meaningful drug interactions have occurred with
concomitant medications and include, but are not limited to, the
following:
Agents That May Affect Carbamazepine Plasma
Levels
CYP 3A4 inhibitors inhibit carbamazepine metabolism and can thus
increase plasma carbamazepine levels. Drugs that have been shown, or would be
expected, to increase plasma carbamazepine levels include:
cimetidine, danazol, diltiazem, macrolides, erythromycin, troleandomycin,
clarithromycin, fluoxetine, fluvoxamine, nefazodone, loratadine, terfenadine,
isoniazid, niacinamide, nicotinamide, propoxyphene, azoles (e.g., ketoconazole,
itraconazole, fluconazole), acetazolamide, verapamil, grapefruit juice, protease
inhibitors, valproate.*
CYP 3A4 inducers can increase the rate of carbamazepine metabolism. Drugs
that have been shown, or that would be expected, to decrease plasma
carbamazepine levels include:
cisplatin, doxorubicin HCl, felbamate,† rifampin,
phenobarbital, phenytoin, primidone, methsuximide, theophylline.
When carbamazepine is given with drugs that can increase or decrease
carbamazepine levels, close monitoring of carbamazepine levels is indicated and
dosage adjustment may be required.
* increased levels of the active 10,11-epoxide
† decreased levels of carbamazepine and increased
levels of the 10,11-epoxide
Effect of Carbamazepine on Plasma Levels of
Concomitant Agents
Increased levels: clomipramine HCl, phenytoin, primidone
Carbamazepine induces hepatic CYP activity. Carbamazepine causes, or would be
expected to cause, decreased levels of the following:
acetaminophen, alprazolam, dihydropyridine calcium channel blockers (e.g.,
felodipine), cyclosporine, corticosteroids (e.g., prednisolone, dexamethasone),
clonazepam, clozapine, dicumarol, doxycycline, ethosuximide, haloperidol,
itraconazole, lamotrigine, levothyroxine, methadone, methsuximide, midazolam,
olanzapine, oral and other hormonal contraceptives, oxcarbazepine, phensuximide,
phenytoin, praziquantel, protease inhibitors, risperidone, theophylline,
tiagabine, topiramate, tramadol, tricyclic antidepressants (e.g., imipramine,
amitriptyline, nortriptyline), valproate, warfarin, ziprasidone, zonisamide.
In concomitant use with carbamazepine, dosage adjustment of the above agents
may be necessary.
Coadministration of carbamazepine with nefazodone results in insufficient
plasma concentrations of nefazodone and its active metabolite to achieve a
therapeutic effect. Coadministration of carbamazepine with nefazodone is
contraindicated (see CONTRAINDICATIONS).
Concomitant administration of carbamazepine and lithium may increase the risk
of neurotoxic side effects.
Alterations of thyroid function have been reported in combination therapy
with other anticonvulsant medications.
Concomitant use of carbamazepine with hormonal contraceptive products (e.g.,
oral, and levonorgestrel subdermal implant contraceptives) may render the
contraceptives less effective because the plasma concentrations of the hormones
may be decreased. Breakthrough bleeding and unintended pregnancies have been
reported. Alternative or back-up methods of contraception should be
considered.
Carcinogenesis, Mutagenesis, Impairment of
Fertility
Carbamazepine, when administered to Sprague-Dawley rats for two
years in the diet at doses of 25, 75, and 250 mg/kg/day, resulted in a
dose-related increase in the incidence of hepatocellular tumors in females and
of benign interstitial cell adenomas in the testes of males.
Carbamazepine must, therefore, be considered to be carcinogenic in
Sprague-Dawley rats. Bacterial and mammalian mutagenicity studies using
carbamazepine produced negative results. The significance of these findings
relative to the use of carbamazepine in humans is, at present, unknown.
Usage in PregnancyTeratogenic EffectsPregnancy category D
(See WARNINGS.)
Labor and Delivery
The effect of carbamazepine on human labor and delivery is
unknown.
Nursing Mothers
Carbamazepine and its epoxide metabolite are transferred to
breast milk. The ratio of the concentration in breast milk to that in maternal
plasma is about 0.4 for carbamazepine and about 0.5 for the epoxide. The
estimated doses given to the newborn during breast-feeding are in the range of 2
to 5 mg daily for carbamazepine and 1 to 2 mg daily for the epoxide.
Because of the potential for serious adverse reactions in nursing infants
from carbamazepine, a decision should be made whether to discontinue nursing or
to discontinue the drug, taking into account the importance of the drug to the
mother.
Pediatric Use
Substantial evidence of carbamazepine’s effectiveness for use in
the management of children with epilepsy (see INDICATIONS AND
USAGE for specific seizure types) is derived from clinical investigations
performed in adults and from studies in several in
vitro systems which support the conclusion that (1) the pathogenetic
mechanisms underlying seizure propagation are essentially identical in adults
and children, and (2) the mechanism of action of carbamazepine in treating
seizures is essentially identical in adults and children.
Taken as a whole, this information supports a conclusion that the generally
accepted therapeutic range of total carbamazepine in plasma (i.e., 4 to 12
mcg/mL) is the same in children and adults.
The evidence assembled was primarily obtained from short-term use of
carbamazepine. The safety of carbamazepine in children has been systematically
studied up to 6 months. No longer-term data from clinical trials is
available.
Geriatric Use
No systematic studies in geriatric patients have been conducted.