Relative bioavailability of oral dosage forms of tenoxicam

The bioavailability of tenoxicam (Ro 12-0068, Tilcotil, CAS 59804-37-4) from an effervescent tablet and an instant milk drink formulation relative to the commercial 20 mg tablet was investigated in a randomized cross-over study. Twelve healthy male volunteers (age 18-35 years; weight 63-95 kg) received on three different occasions a single oral tablet, an effervescent tablet or an instant milk drink (dissolved in water) with each dose containing 20 mg of tenoxicam. The wash-out period between two consecutive treatments was at least 5 weeks. Plasma concentrations after dosing were determined with a specific HPLC method. With the effervescent tablet and the milk drink, maximum concentrations were obtained at the same time (0.5-3.0 h) as with the reference tablet (0.5-4.0 h). Plasma peak concentrations appeared highest after the commercial tablet (mean +/- SD: Cmax 2.8 +/- 0.55 mg/l), but the difference to the effervescent tablet (2.7 +/- 0.41 mg/l) and the milk formulation (2.5 +/- 0.41 mg/l) was negligible. Similar mean elimination half-lives of 73, 77, and 77 h were obtained with the effervescent tablet, the milk drink, and the commercial tablet, respectively. Average bioavailability relative to the tablet was for the effervescent tablet and for the milk drink 96% with a coefficient of variation of 8%. The 90%-confidence intervals of the mean differences between the test and standard preparations in log-transformed AUC0-infinity and Cmax were within 20% around the respective mean parameter value calculated for the standard preparation allowing to conclude bioequivalence of the three oral formulations.