Bioavailability and Pharmacokinetics of Once-Daily Amantadine Extended-Release Tablets in Healthy Volunteers: Results from Three Randomized, Crossover, Open-Label, Phase 1 Studies

INTRODUCTION: In February 2018, OS320—an amantadine extended-release (ER) tablet formulation with once-daily morning administration—was approved for the treatment of Parkinson’s disease and drug-induced extrapyramidal reactions in adults. The purpose of this study was to describe three phase 1 studies that assessed the pharmacokinetics (PK) and bioavailability of amantadine ER in healthy adult volunteers. METHODS: Study 1 was an open-label, four-treatment, single-dose, crossover study comparing amantadine ER 129, 193, and 258 mg tablets with an equivalent dose of immediate-release (IR) amantadine 40 mg/5 mL syrup. Study 2 was an open-label, single-dose, crossover food-effect study with amantadine ER 258 mg. Study 3 was an open-label, multiple-dose, crossover study comparing amantadine ER and amantadine IR syrup. RESULTS: Amantadine ER displayed a steady release of amantadine, with the peak amantadine concentration occurring at ~ 7.5 h postdose or in the middle of the day (following a morning dose) with steady-state administration. Administration of amantadine ER 258 mg with a high-fat meal did not affect amantadine bioavailability. Amantadine plasma exposure increased proportionally with increasing doses, and at steady state, amantadine exposure from an amantadine ER 258-mg tablet was bioequivalent to twice-daily 129-mg amantadine IR syrup. CONCLUSION: The PK profile of amantadine ER 129-mg, 193-mg, and 258-mg tablets allows for once-daily dosing in the morning; the 24-h average amantadine plasma concentration is equivalent to that for the same daily dose of IR amantadine administered twice daily. FUNDING: Osmotica Pharmaceutical US LLC.