Plasma and synovial fluid concentrations of piroxicam during prolonged treatment with piroxicam pivalic ester.

Piroxicam pivalic ester (CHF 10/21) is a prodrug of piroxicam and is characterized by a reduced gastric irritant activity. Plasma and synovial fluid samples were simultaneously taken from 7 patients with mono- or poly-articular arthritis causing knee effusion, during 4 weeks of treatment with CHF 10/21 at the dose of 30 mg/day. The time courses of plasma levels of both the prodrug and the active principle were studied and a correlation of the latter with synovial fluid levels was made. After 14 days of treatment the steady-state was reached in the systemic (plasma) and peripheral (synovial fluid) compartments with therapeutically active drug levels. Clinical results were good and a complete disappearance of local pain occurred in 2 cases. Good gastric tolerance was also achieved.