Relative bioavailability of a controlled-release albuterol formulation for twice-daily use.

A two-way-crossover bioavailability study was completed with 15 healthy male volunteers to evaluate the relative bioavailability of an orally administered controlled-release (CR) formulation of albuterol as compared to the immediate-release (IR) formulation of albuterol. The CR formulation of albuterol used in this study was based mechanistically on the elementary osmotic pump. Each subject received one 8 mg CR tablet every 12 h for 8 consecutive days and one 4 mg IR tablet every 6 h for 8 consecutive days, with 7 days separating each phase. During day 8 of dosing, hourly blood samples (0-12 h) were collected after the morning dose and three additional samples were obtained 16, 20 and 24 h following this dose. Plasma concentrations were measured using a gas chromatography-mass spectrometry procedure. No statistically significant differences were observed in mean steady-state values for Cmax, Cmin, AUC(0-12 h) and peak-to-trough fluctuations (PTF) in comparing the two dosage formulations. Mean steady state Tmax values were 2.6 and 6.0 h for the TR and CR formulations, respectively. It was concluded that twice daily administration of the controlled-release formulation of albuterol provides an alternative to four times daily administration of conventional (immediate-release) albuterol tablets.