Antimycobacterial drugs and the production of reactive oxidants by polymorphonuclear leucocytes in vitro.

The effect of five antimycobacterial drugs isoniazid, rifampicin, streptomycin, pyrazinamide and ethambutol on the generation of reactive oxidants by polymorphonuclear leucocytes was investigated in vitro, using N-formyl-L-methionyl-L-leucyl-phenylalanine (FMLP) activated and spontaneous luminol-enhanced chemiluminescence and myeloperoxidase-mediated iodination. Streptomycin, pyrazinamide and ethambutol had no effect on the assays at the concentrations investigated. Isoniazid as concentrations of 1.25 and 5 micrograms/ml and rifampicin at 100 micrograms/ml significantly inhibited iodination. Rifampicin also caused dose-dependent inhibition of chemiluminescence which was partly due to its light-absorbing activities. It is concluded that isoniazid, and to a lesser extent, rifampicin at therapeutic concentrations possess anti-oxidative properties.