COMPARATIVE BIOAVAILABILITY OF THEOPHYLLINE FROM TABLETS WITH DIFFERENT SUSTAINED-RELEASE KINETICS

The overall objective of this study was to correlate the in vitro drug release from several sustained release tablets with their in vivo ava ilability in beagle dogs as an animal model. The formulations containe d 50% theophylline, 30% sustained release agent, 0.5% lubricant (where necessary), and the remaining were excipients. The sustained release agents were Compritol, glyceryl behenate, Klucel HXF, hydroxypropyl ce llulose and Carbopol 934P, carbomer. The excipients were spray dried l actose, anhydrous calcium phosphate, A-TAB and microcrystalline cellul ose, Avicel PH 101. The sustained release agent containing tablets pro vided much slower drug release in vivo than the respective control tab lets. This effect was greatest for glyceryl behenate formulations and smallest for hydroxypropyl cellulose. The in vivo and in vitro results demonstrated a 1/1 correlation only if the drug release profiles in v itro was independent of the test condition.