Selegiline Hcl 5 mg · Tablets

Selegiline is an irreversible inhibitor of monoamine oxidase (MAO), which regulates the metabolic degradation of catecholamines and serotonin in the central nervous system and peripheral tissues. At recommended doses, selegiline is selective for MAO type B (MAO-B), the major form in the brain. Inhibition of MAO-B activity, by blocking the catabolism of dopamine, may result in increased dopamine levels; however, there is evidence that selegiline may act through other mechanisms to increase dopaminergic activity.

Absorption — ZELAPAR disintegrates within seconds after placement on the tongue and is rapidly absorbed. Detectable levels of selegiline from ZELAPAR have been measured at 5 minutes after administration, the earliest time point examined.

Selegiline is more rapidly absorbed from the 1.25 or 2.5 mg dose of ZELAPAR (Tmax range: 10-15 minutes) than from the swallowed 5 mg selegiline tablet (Tmax range: 40-90 minutes). Mean (SD) maximum plasma concentrations of 3.34 (1.68) and 4.47 (2.56) ng/mL are reached after single dose of 1.25 and 2.5 mg ZELAPAR compared to 1.12 ng/mL (1.48) for the swallowed 5 mg selegiline tablets (given as 5 mg bid). On a dose-normalized basis, the relative bioavailability of selegiline from ZELAPAR is greater than from the swallowed formulation.

The pre-gastric absorption from ZELAPAR and the avoidance of first-pass metabolism results in higher concentrations of selegiline and lower concentrations of the metabolites compared to the 5 mg swallowed selegiline tablet.

Plasma Cmax and AUC of ZELAPAR were dose proportional at doses between 2.5 and 10 mg daily.

Food Effects — When ZELAPAR is taken with food, the Cmax and AUC of selegiline are about 60% of those seen when ZELAPAR is taken in the fasted state. Since ZELAPAR is placed on the tongue and absorbed through the oral mucosa, the intake of food and liquid should be avoided 5 minutes before and after ZELAPAR administration [see Dosage and Administration (2.1)].

Distribution — Up to 85% of plasma selegiline is reversibly bound to proteins.

Metabolism — Following a single dose, the median elimination half-life of selegiline was 1.3 hours at the 1.25 mg dose. Under steady-state conditions, the median elimination half-life increases to 10 hours. Upon repeat dosing, accumulation in the plasma concentration of selegiline is observed both with ZELAPAR and the swallowed 5 mg tablet. Steady state is achieved after 8 days.

Selegiline is metabolized in vivo to l-methamphetamine and N-desmethylselegiline and subsequently to l-amphetamine; which in turn are further metabolized to their hydroxymetabolites.

ZELAPAR also produces a smaller fraction of the administered dose recoverable as the metabolites than the conventional, swallowed formulation of selegiline.

In vitro metabolism studies indicate that CYP2B6 and CYP3A4 are involved in the metabolism of selegiline. CYP2A6 may play a minor role in the metabolism.

Elimination — Following metabolism in the liver, selegiline is excreted primarily in the urine as metabolites (mainly as l-methamphetamine) and as a small amount in the feces.

Specific Populations — Age: The effect of age on the pharmacokinetics of selegiline following ZELAPAR administration has not been adequately characterized.

Gender: There are no differences between male and female subjects in overall (AUC∞), time to maximum exposure (Tmax), and elimination half-life (t½) after administration of ZELAPAR. Female subjects have an approximate 25% decrease in Cmax compared to male subjects. However, since the overall exposure (AUC∞) is not different between the genders, this pharmacokinetic difference is not likely to be clinically relevant.

Race: No studies have been conducted to evaluate the effects of race on the pharmacokinetics of ZELAPAR.

Renal Impairment: Following once-daily dosing of ZELAPAR 2.5 mg to selegiline steady-state (10 days) in 6 subjects with mild renal impairment (CLcr >50 to 89 mL/min) and in 6 subjects with moderate renal impairment (CLcr >30 to 50 mL/min), AUC and Cmax of selegiline and desmethylselegiline were not substantially different from healthy subjects; however, methamphetamine and amphetamine exposures were increased by 34-67% in subjects with moderate renal impairment. Following once-daily dosing of ZELAPAR 1.25 mg to steady-state (10 days) in 6 end-stage renal disease patients, off dialysis, selegiline exposure was not substantially different from that in healthy subjects, however methamphetamine and amphetamine exposures were increased approximately 4-fold compared to healthy subjects [see Dosage and Administration (2.3) and Use in Specific Populations (8.7)].