Drug efficiency studies were performed with pentamidine isethionate and phosphatidylcholine-liposomes (PCC-lip), a new formula manufactured by Rhone-Poulenc Rorer. Both drugs were tested individually or in combination in a system of Pneumocystis carinii culture without a feedercell layer, using a modification of TEGOSHI's medium (1989). The source of P. carinii were nude rats, which develop spontaneously Pneumocystis pneumonia. The number of trophozoites of P. carinii was used as the criterium for growth and drug effects. The results show a rapid decrease of parasites in cultures with PPC and pentamidine (Pentacarinat), while trophozoites in control cultures were well preserved for up to five days. The survival of the parasites is dose-dependent. If the concentration of PPC is reduced the trophozoites stay intact for a longer time. The combination of pentamidine and PPC-lip was more effective than each drug alone. Already after 24 hours of culture the combination of PPC-lip (0.1 mg/ml) and pentamidine 0.015 mg/ml) reduces the number of trophozoites to 20% compared to control cultures. The results were confirmed by electron microscopy.

*Pentamidine/TOXICITY *Pneumocystis carinii/DRUG EFFECTS

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