Overview on the pharmacokinetics of tenoxicam

Tenoxicam, a new non-steroidal anti-inflammatory drug (NSAID) with an oxicam structure, is entirely ionised at physiological pH, has minimal lipophilic properties, high plasma protein binding, does not accumulate in fatty tissue and skin and thus has a small volume of distribution. Tenoxicam is rapidly and completely absorbed after oral administration. It is entirely metabolised via oxidation and conjugation pathways before elimination. The extraction ratio in the liver is small resulting in a long elimination half-life with a mean of 72 hours. Since no unchanged drug is found in the bile the low half-life cannot be explained by enterohepatic recirculation of parent compound. The low elimination rate of tenoxicam allows for a once-daily dosage (20 mg) regimen. Following multiple dosing during the first two weeks of therapy tenoxicam reaches steady-state levels within 10-20% of predicted values. Several pharmacokinetic factors help make tenoxicam therapy safe and straightforward: it is completely absorbed when taken orally even with meals or antacids, it penetrates easily into synovial fluid, and is excreted as inactive metabolites. Furthermore, drug disposition is not influenced by age, sex or rheumatic disease and unexpected accumulation is not observed.