The absolute bioavailability of a new pediatric sustained release theophylline tablet, when given as whole or divided tablets

Abstract

Absorption characteristics and absolute bioavailability of a new sustained release theophylline tablet for pediatric use were investigated in seven volunteers, both after administration of whole tablets and tablets broken into four equal parts. An intravenous infusion of 200 mg theophylline (as aminophylline) was also administered to the same panel of subjects. Theophylline plasma concentrations were measured frequently during a period of 33 h post dosing. Both after intake of the whole and the broken tablets steadily increasing theophylline plasma concentrations were found. The maximum concentration was found after 5.2 +/- 0.6 h (mean +/- S.D.) and 5.3 +/- 2.2 h and measured 2.00 +/- 0.28 mg.1-1 and 2.46 +/- 0.60 mg.1-1, respectively. The absorption process continued for a considerable period. As a consequence the theophylline plasma concentrations remained above 75% of the maximum value during a period of 8.9 +/- 2.1 h and 8.6 +/- 2.0 h. The absolute bioavailability of the whole tablets was 91.8 +/- 24.7% and that of the broken tablets was 95.8 +/- 9.7%.