Steady-state pharmacokinetics and bioequivalence study of quetiapine fumarate film-coated tablets 300 mg in adult schizophrenic patients

Quetiapine is a dibenzothiazepine derivative approved for the treatment of schizophrenia and related psychoses. The objective of the present study was to design and evaluate the bioequivalence between quetiapine fumarate film-coated tablets of Dr. Reddy’s Laboratories Ltd., Hyderabad, India (test) and Seroquel® tablets (containing quetiapine) of AstraZeneca Pharmaceuticals LP Wilmington, DE, USA (reference). It was a two-way crossover steady-state multiple dose study in 54 adult schizophrenic patients under fasting conditions. Quetiapine was analyzed in plasma samples by using a validated liquid chromatographic mass spectrometry (LC-MS/MS) method. The pharmacokinetic parameters were estimated by noncompartmental method and mean (±SD) of Cmax,ss (ng/mL) for test and reference products were 1436.5 (±810.2) and 1413.1 (±905.5), respectively. The mean (±SD) of AUCτ,ss (ng·h/mL) for test and reference products were 6949.8 (±3879.8) and 6532.2 (±4279.4), respectively. The ratio of least square means and its 90% confidence interval for Cmax,ss and AUCτ,ss were found to be within bioequivalence limits 80.00–125.00%. In conclusion, test product was bioequivalent to the reference product in terms of both rate and extent of absorption under steady-state conditions.