The analgesic activity of tramadol is due to both parent drug and the M1 metabolite. Tramadol Hydrochloride Extended-Release Capsules are administered as a racemate and both tramadol and M1 are detected in the circulation. The C
max and AUC of Tramadol Hydrochloride Extended-Release Capsules have been observed to be dose-proportional over an oral dose range of 100 to 300 mg in healthy subjects.
Absorption
After a single dose administration of Tramadol Hydrochloride Extended-Release Capsules, T
max occurs around 10-12 hours.
The mean C
max and AUC of Tramadol Hydrochloride Extended-Release Capsules after a 300 mg single dose was 308 ng/mL and 6777 ng*hr/mL, respectively under fasting conditions. Tramadol Hydrochloride Extended-Release Capsules are bioequivalent to a reference extended-release tramadol product following a single 300 mg dose under fasting conditions.
At steady-state, Tramadol Hydrochloride Extended-Release Capsules at 200 mg has been observed to be bioequivalent to a reference extended-release tramadol product at 200 mg under fasting conditions (Table 2). Following administration of Tramadol Hydrochloride Extended-Release Capsules 200 mg capsules, steady-state plasma concentrations of both tramadol and M1 are achieved within four days of once daily dosing.
Table 3.
AUC
0-24: Area Under the Curve in a 24-hour dosing interval
|
C
max: Peak Concentration in a 24-hour dosing interval
|
C
min: Trough Concentration in a 24-hour dosing interval
|
T
max: Time to Peak Concentration
|
Mean (%CV) Steady-State Pharmacokinetic Parameter Values (N= 38)
|
| Tramadol | O-Desmethyl-Tramadol (M1 Metabolite) |
| Parameter | Tramadol Hydrochloride Extended Release Capsules 200 mg | A Reference Extended-Release Tramadol Product 200 mg | Tramadol Hydrochloride Extended
Release
Capsules 200 mg
| A Reference Extended-Release Tramadol Product
200 mg
|
| AUC
0-24(ng.h/mL)
| 5678 (27%) | 5563 (32%) | 1319 (34%) | 1302 (40%) |
| C
max(ng/mL)
| 332 (25%) | 350 (31%) | 70 (34%) | 74 (41%) |
C
min (ng/mL)
| 128 (39%) | 125 (45%) | 35 (34%) | 33 (42%) |
| T
max | 5.9 (66%) | 10 (30%) | 11 (37%) | 13 (29%) |
| % Fluctuation | 88 (19%) | 101 (30%) | 64 (22%) | 76 (30%) |
Food Effect
The rate and extent of absorption of Tramadol Hydrochloride Extended-Release Capsules (300 mg) are similar following oral administration with or without food. Therefore, Tramadol Hydrochloride Extended-Release Capsules can be administered without regard to meals.
Distribution
The volume of distribution of tramadol was 2.6 and 2.9 liters/kg in male and female subjects, respectively, following a 100 mg intravenous tramadol dose. The binding of tramadol to human plasma proteins is approximately 20% and binding also appears to be independent of concentration up to 10 mcg/mL. Saturation of plasma protein binding occurs only at concentrations outside the clinically relevant range.
Elimination
Tramadol is eliminated primarily through metabolism by the liver and the metabolites are eliminated primarily by the kidneys. The mean plasma elimination half-lives of racemic tramadol and racemic M1 after administration of Tramadol Hydrochloride Extended-Release Capsules are approximately 10 and 11 hours, respectively.
Metabolism
Tramadol is extensively metabolized after oral administration. The major metabolic pathways appear to be N – (mediated by CYP3A4 and CYP2B6) and O – (mediated by CYP2D6) demethylation and glucuronidation or sulfation in the liver. One metabolite (O-desmethyl tramadol, denoted M1) is pharmacologically active in animal models. Formation of M1 is dependent on CYP2D6 and as such is subject to inhibition and polymorphism, which may affect the therapeutic response
[see Drug Interactions (7)]
.
Excretion
Approximately 30% of the dose is excreted in the urine as unchanged drug, whereas 60% of the dose is excreted as metabolites. The remainder is excreted either as unidentified or as unextractable metabolites.
Special Populations
Hepatic Impairment
Pharmacokinetics of tramadol was studied in patients with mild or moderate hepatic impairment after receiving multiple doses of an extended-release tramadol product at 100 mg. The exposure of (+)- and (-)-tramadol was similar in mild and moderate hepatic impairment patients in comparison to patients with normal hepatic function. However, exposure of (+)- and (-)-M1 decreased ~50% with increased severity of the hepatic impairment (from normal to mild and moderate). The pharmacokinetics of tramadol has not been studied in patients with severe hepatic impairment. After the administration of tramadol immediate-release tablets to patients with advanced cirrhosis of the liver, tramadol area under the plasma concentration time curve was larger and the tramadol and M1 half-lives were longer than subjects with normal hepatic function. The limited availability of dose strengths of Tramadol Hydrochloride Extended-Release Capsules does not permit the dosing flexibility required for safe use in patients with severe hepatic impairment. Therefore, Tramadol Hydrochloride Extended-Release Capsules should not be used in patients with severe hepatic impairment
[see Use in Specific Populations (
8.6)].
Renal Impairment
Impaired renal function results in a decreased rate and extent of excretion of tramadol and its active metabolite, M1. The pharmacokinetics of tramadol was studied in patients with mild or moderate renal impairment after receiving multiple doses of an extended-release tramadol product at 100 mg. There is no consistent trend observed for tramadol exposure related to renal function in patients with mild (CL
cr: 50-80 mL/min) or moderate (CL
cr: 30-50 mL/min) renal impairment in comparison to patients with normal renal function (CL
cr > 80 mL/min). However, exposure of M1 increased 20-40% with increased severity of the renal impairment (from normal to mild and moderate). The pharmacokinetics of tramadol has not been studied in patients with severe renal impairment (CL
cr < 30 mL/min). The limited availability of dose strengths of Tramadol Hydrochloride Extended-Release Capsules does not permit the dosing flexibility required for safe use in patients with severe renal impairment. Therefore, Tramadol Hydrochloride Extended-Release Capsules should not be used in patients with severe renal impairment. The total amount of tramadol and M1 removed during a 4-hour dialysis period is less than 7% of the administered dose
[see Use in Specific Populations (
8.6)].
Sex
Based on pooled multiple-dose pharmacokinetics studies for an extended-release tramadol product in 166 healthy subjects (111 males and 55 females), the dose-normalized AUC values for tramadol were somewhat higher in females than in males. There was a considerable degree of overlap in values between male and female groups. Dosage adjustment based on sex is not recommended.
Age: Geriatric Population
The effect of age on pharmacokinetics of Tramadol Hydrochloride Extended-Release Capsules have not been studied. Healthy elderly subjects aged 65 to 75 years administered an immediate-release formulation of tramadol, have plasma concentrations and elimination half-lives comparable to those observed in healthy subjects younger than 65 years of age. In subjects over 75 years, mean maximum plasma concentrations are elevated (208 vs. 162 ng/mL) and the mean elimination half-life is prolonged (7 vs. 6 hours) compared to subjects 65 to 75 years of age. Adjustment of the daily dose is recommended for patients older than 75 years
[see Dosage and Administration (
2.3)].
Drug Interaction Studies
Potential for Tramadol to Affect Other Drugs
In vitro studies indicate that tramadol is unlikely to inhibit the CYP3A4-mediated metabolism of other drugs when tramadol is administered concomitantly at therapeutic doses. Tramadol does not appear to induce its own metabolism in humans, since observed maximal plasma concentrations after multiple oral doses are higher than expected based on single-dose data.
Poor / Extensive Metabolizers, CYP2D6
The formation of the active metabolite, M1, is mediated by CYP2D6, a polymorphic enzyme. Approximately 7% of the population has reduced activity of the CYP2D6 isoenzyme of cytochrome P-450 metabolizing enzyme system. These individuals are “poor metabolizers” of debrisoquine, dextromethorphan and tricyclic antidepressants, among other drugs. Based on a population PK analysis of Phase 1 studies with IR tablets in healthy subjects, concentrations of tramadol were approximately 20% higher in "poor metabolizers" versus "extensive metabolizers," while M1 concentrations were 40% lower.
CYP2D6 Inhibitors
In vitro drug interaction studies in human liver microsomes indicate that concomitant administration with inhibitors of CYP2D6 such as fluoxetine, paroxetine, and amitriptyline could result in some inhibition of the metabolism of tramadol.
Quinidine
Tramadol is metabolized to active metabolite M1 by CYP2D6. Coadministration of quinidine, a selective inhibitor of CYP2D6, with tramadol ER resulted in a 50-60% increase in tramadol exposure and a 50-60% decrease in M1 exposure. The clinical consequences of these findings are unknown.
To evaluate the effect of tramadol, a CYP2D6 substrate on quinidine, an
in vitro drug interaction study in human liver microsomes was conducted. The results from this study indicate that tramadol has no effect on quinidine metabolism.
[see Warnings and Precautions (5.1,
5.5), Drug Interactions (
7)
].
CYP3A4 Inhibitors and Inducers
Since tramadol is also metabolized by CYP3A4, administration of CYP3A4 inhibitors, such as ketoconazole and erythromycin, or CYP3A4 inducers, such as rifampin and St. John’s Wort, with Tramadol Hydrochloride Extended-Release Capsules may affect the metabolism of tramadol leading to altered tramadol exposure
[see Warnings and Precautions (5.1,
5.5), Drug Interactions (
7)].
Cimetidine
Concomitant administration of tramadol immediate-release tablets with cimetidine, a weak CPY3A4 inhibitor, does not result in clinically significant changes in tramadol pharmacokinetics. No alteration of the Tramadol Hydrochloride Extended-Release Capsules dosage regimen with cimetidine is recommended.
Carbamazepine
Carbamazepine, a CYP3A4 inducer, increases tramadol metabolism. Patients taking carbamazepine may have a significantly reduced analgesic effect of tramadol. Concomitant administration of Tramadol Hydrochloride Extended-Release Capsules and carbamazepine is not recommended
.