Bioequivalence Study of Two Formulations of Flunarizine Hydrochloride Capsules in Healthy Chinese Subjects Under Fasting and Fed Conditions.

Background And Objectives: Flunarizine, a selective calcium channel blocker with vasodilatory and neuroprotective effects, is a mainstay for migraine prophylaxis and vertigo management. This study aimed to compare the bioequivalence, pharmacokinetics, and safety of test and reference flunarizine hydrochloride capsules after a single oral dose under fasting/fed conditions.

Methods: A randomized, open-label, two-formulation, single-dose, two-period crossover bioequivalence study was conducted under fasting and fed conditions. Eligible healthy Chinese subjects received a single 5-mg dose of the test or reference flunarizine hydrochloride capsules, followed by a 21-day washout interval between periods. Blood samples were collected up to 36 h post-dose. Pharmacokinetic parameters were calculated using noncompartmental methods, and bioequivalence was assessed via geometric mean ratios of the test/reference for primary pharmacokinetic parameters, along with 90% confidence intervals. Tolerability was evaluated during the entire study period.

Results: Twenty-four volunteers completed the fasting study, while 42 volunteers completed the fed study. The test formulation demonstrated bioequivalence to the marketed formulation, with 90% confidence intervals for geometric mean ratios of peak plasma concentration (fasting: 97.38-106.57%; fed: 92.71-109.58%), area under the curve from time 0 to 36 h (fasting: 98.20-108.09%; fed: 93.79-100.81%), and AUC from time 0 to infinity (fasting: 97.88-107.30%; fed: 93.63-100.53%), all within equivalence limits of 80.00-125.00%. High-fat meals delayed the time to maximum concentration by 2.5 h and increased exposure by 20%. Both the test and reference formulations were well tolerated, and no serious adverse events related to the study drug were reported during the study.

Conclusions: This study confirmed that test and reference flunarizine hydrochloride capsules were bioequivalent under fasting and fed conditions.

Clinical Trial Registration: ChiCTR1900026713.