Efficacy of tetroxoprim/sulphadiazine in the treatment of Pneumocystis carinii pneumonitis in rats.

Pneumocystis carinii pneumonitis was induced using dexamethasone in male Sprague-Dawley rats. After the first death due to Pn. carinii occurred, nine rats received 50 mg/kg/day tetroxoprim and 120 mg/kg/day sulphadiazine. Four additional rats were given no therapy and served as a positive control. All the surviving rats including five negative controls were sacrificed four weeks after the last positive control rat died. All four rats in the positive control group and two of nine in the treated group developed Pn. carinii pneumonitis, whereas none of the five negative controls had evidence of Pn. carinii infection. The difference between the treated and untreated rats was significant (P = 0.05). These results suggest that combination therapy with tetroxoprim/sulphadiazine is effective in the treatment of Pn. carinii pneumonitis in this animal model.