RELATIVE POTENCY OF 10 DRUGS WITH ANTIPNEUMOCYSTIS CARINII ACTIVITY IN AN ANIMAL-MODEL

Several drugs have been shown to have anti-Pneumocystis carinii activi ty in clinical trials. Because of the large number of patients require d, no more than 3 drugs can be compared for efficacy in human studies. However, the experimental animal model for P. carinii pneumonitis is remarkably similar to the human disease and was used to compare 10 dru gs for the relative potency against this infection. All drugs were com pared at doses known to prevent the pneumonitis in > 80% of animals an d at one-tenth of this dose. Drugs effective at the lowest dose were f urther tested at one-hundredth the original doses, and drugs ineffecti ve were retested at 10 and 100 times the original dose. Trimethoprim-s ulfamethoxazole was the most effective drug, with azithromycin-sulfame thoxazole and clarithromycin-sulfamethoxazole next most effective. Int ravenous pentamidine and clindamycin-primaquine were the least effecti ve. Atovaquone, sulfadoxine-pyrimethamine, erythromycin-sulfisoxazole, PS-15, and dapsone-trimethoprim had intermediate activity.