Pentamidine aerosol in prophylaxis and treatment of murine Pneumocystis carinii pneumonia

The efficacy and tolerance of pentamidine aerosol were evaluated in the prophylaxis and therapy of murine Pneumocystis carinii pneumonia. P. carinii pneumonia was induced in rats by corticosteroid immunosuppression. Pentamidine was administered three times weekly via a Bird micronebulizer. The actual amount of pentamidine inhaled was estimated by monitoring the ventilation of the rats during the aerosol administration. Pentamidine levels in blood, lung, liver and kidney samples were determined by high-pressure liquid chromatography after completion of the treatment. Efficacy was evaluated by examination of lung imprints. In the prophylactic treatment, 4.8- and 8.6-mg/kg doses of aerosolized pentamidine administered three times weekly for 7 weeks were effective in preventing P. carinii pneumonia in 80 and 100% of the rats, respectively. In the therapeutic studies, a 14.6-mg/kg dose of aerosolized pentamidine administered three times weekly for 3 weeks was effective both in curing the pneumonia and in clearing P. carinii cysts in 70% of the rats. In the remaining animals, although the pneumonia was cured, the cysts persisted. A dose-dependent effect of the drug was demonstrated in both prophylactic and therapeutic treatments. High lung/kidney and lung/liver ratios of pentamidine levels were demonstrated and were associated with good clinical, biological, and histologic tolerance.