Serum and synovial fluid levels of angiotensin converting enzyme in polyarthritis.

Serum levels of angiotensin converting enzyme (ACE) activity in patients with rheumatoid arthritis (RA) (n = 48), osteoarthritis (OA) (n = 11), ankylosing spondylitis (n = 24), psoriatic arthritis (n = 12), and Behçet's syndrome (n = 20) were not significantly different from those of normal controls (n = 26). Synovial fluid ACE activity was lower in OA than in RA but was similar when corrected for protein levels. An increase in serum ACE concentration in patients with RA receiving captopril therapy is in agreement with previous results. There was some correlation of ACE with erythrocyte sedimentation rate (ESR) and C reactive protein (CRP) but not with clinical indices in captopril treated patients. It is suggested that the beneficial actions of captopril in the treatment of RA are not due to its activity as an ACE inhibitor, but more probably a result of captopril being an aliphatic thiol.

A pharmacokinetic comparison of tenoxicam in plasma and synovial fluid.

In view of the paucity of information of the synovial fluid pharmacokinetics of nonsteroidal anti-inflammatory drugs with a long half-life, we have compared the pharmacokinetics of tenoxicam (TILCOTIL, MOBIFLEX) in plasma and synovial fluid in six patients with polyarthritis causing knee effusion. Plasma and synovial fluid concentrations of tenoxicam were measured up to 96 hours after an oral dose of a single 40 mg tablet. A full pharmacokinetic analysis was performed. Tenoxicam passed into synovial fluid attaining a peak concentration significantly later than that for plasma. However, the mean half-life for synovial fluid (45 hours) was not significantly different from that for plasma (42 hours). Comparison of area under the curve (AUC) indicated the total exposure of the synovial fluid to tenoxicam was consistent in different patients, comprising 50-60% of the corresponding plasma levels in every case. In the case of tenoxicam, synovial fluid exhibits the pharmacokinetic properties of a peripheral "tissue" compartment.