Bioavailability of rifampicin, isoniazid and pyrazinamide from fixed-dose combination capsules.

SETTING The absorption of rifampicin, isoniazid and pyrazinamide was tested after administration of each drug in free combinations and in a fixed-dose combination of the three drugs, known as Trifazid. OBJECTIVE To examine the relative bioavailability of rifampicin, isoniazid and pyrazinamide after oral administration of the drugs given alone in comparison to that of the same drugs after administration of Trifazid. DESIGN An open, randomized, cross-over study comprising 16 healthy volunteers. RESULTS The pattern of absorption, plasma concentrations and pharmacokinetic parameters were very similar after administration of the drugs in free and fixed combinations. CONCLUSION The triple combination of antituberculosis drugs could replace the separate drugs in the treatment of tuberculosis.