Cephalexin levels in serum, synovial fluid and joint tissues after oral administration.

Cephalexin (1 g) was administered orally every 6 hours to 13 patients with rheumatoid arthritis and chronic knee effusions without bacterial arthritis. Samples were taken from blood, synovial fluid, synovium, cartilage and bone. The concentrations found in these samples after one oral dose were high enough to have a possible therapeutic effect in bacterial arthritis sensitive to cephalexin.