Effects of capsicum fruit on theophylline absorption and bioavailability in rabbits.

Absorption and bioavailability of theophylline from a sustained-release gelatin capsule were investigated in 10 male rabbits after oral administration (20 mg/kg), with and without a ground capsicum fruit suspension. Comparison of pharmacokinetic parameters showed that the concomitant absorption of capsicum increases areas under plasma curves (from 86.06 +/- 9.78 mg H/liter to 138.32 +/- 17.27 mg H/liter, P less than 0.001), peak plasma levels (from 6.65 +/- 0.76 to 8.78 +/- 0.98 mg/liter, P less than 0.01), and mean residence times (from 14.94 +/- 2.97 to 20.98 +/- 5.75 H, P less than 0.001). A second administration of the capsicum suspension, 11 hours after dosing, produced a new rise of theophylline plasma levels in every rabbit. The variations in pharmacokinetic and bioavailability parameters are discussed in accordance with the mechanisms of action of capsaicin, an active compound present in capsicum fruit.