In experiments on immunosuppressed mice, effective, longterm prevention of PCP usually requires at least 2 antibiotics used together. An example is the antibiotic erythromycin and a sulpha drug. By itself erythromycin has no anti-PCP effect, but, when used with sulpha drugs, it is effective against PCP in mice. In the late 1980's it was reported that HIV-infected patients given AZT appeared to be at reduced risk for developing PCP compared with others not given AZT, at least in the short term. AZT is also said to have anti-bacterial activity and may prevent Salmonella infections in patients given at least 400 mg/ day of the drug. Researchers at Hopital Claude Bernard in Paris, France, have been conducting experiments with immunosuppressed mice to investigate the anti-PCP potential of AZT. The rat model of immuno-suppression is useful in predicting which drugs are worth testing in humans with PCP. The Paris researchers found that AZT by itself did not have anti-PCP effects. Using AZT with Bactrim/Septra was no more protective than Bactrim/ Septra without AZT. They concluded that "the reduced [short-term] incidence of PCP reported for [subjects] treated with [AZT]" is more likely due to improved immunofunctions than a direct effect of AZT on P. carinii, the cause of PCP. Indeed, in longer, controlled trials of AZT, the drug appeared to provide no significant antiPCP effect. AZT's lack of anti-PCP effect has also been recently confirmed by scientists at the National Cancer Institute and elsewhere in the USA.
REFERENCES:
1. Brun-Pascaud M, Girard P-M and Pocidalo J-J. Low-dose trimethoprim-sulfamethoxazole; sulfamethoxazole alone and in association with Zidovudine for prevention and treatment of murine Pneunocystis carinii pneumonia. Antimicrobial Agents and Chemotherapy 1992;36(10):2328-2330.
2. Walzer PD, Foy J, Steele P, et al. Activities of anti-folate, antiviral and other drugs in an immunosuppressed rat model of Pneumocystis carinii pneumonia. Antimicrobial Agents and Chemotherapy 1992;36(9):1935- 1942.
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