TreatmentUpdate60; Volume 7, No. 6 - June 1995
Sean Hosein

Although drugs such as Bactrim/Septra and intravenous pentamidine are effective against the life-threatening lung infection PCP, they have side effects which some patients cannot tolerate. Researchers are testing a number of antibiotics by themselves or in combination to find alternatives to standard therapy. Scientists working for Glaxo-Wellcome have been testing several combinations of anti-PCP drugs in mice, and we report their results below.

* MICE WITH PCP

Researchers used mice with weakened immune systems who were infected with the microbe that causes PCP. They found that the drugs Mepron(R) (atovaquone, Wellvone(R)) and dapsone had anti-PCP activity when used by themselves. The following combinations had increased anti-PCP activity when used together rather than when used by themselves:

- Mepron and azithromycin - Mepron and clarithromycin

While the antibiotic rifabutin (Mycobutin(R)) had no anti-PCP activity by itself, in combination with Mepron, rifabutin had significantly increased anti-PCP effect. The researchers noted that none of the following drugs weakened the anti-PCP effect of Mepron-azithromycin, B/S, clarithromycin or dapsone.

* Toxo

In other developments, researchers in military biomedical centres and elsewhere in the USA have been testing various compounds for their anti-parasite activity. Results from their work suggest that extracts of the Chinese herb A. annua (quinghaosu) and another antimalarial drug, cycloquanil, can have anti-toxo effects in experiments with cells and parasites. That antimalarial drugs might be useful against the microbes that cause PCP/toxo is not surprising. The drug Mepron was being developed as an antimalarial until its anti-toxo/PCP effects were discovered. Fansidar is another antimalarial that some doctors prescribe to prevent toxo. In the next article we provide details about quinghaosu as an antimalarial drug and its use in the USA for treating PCP.

REFERENCES:

1. Comley JCW and Sterling . Effect of atovaquone and atovaquone drug combinations on prophylaxis for Pneumocystis carinii pneumonia in SCID mice. Antimicrobial Agents and Chemotherapy 1995;39(4):806-81 1.

2. Holfels E, McAuley J, Mack D, et al. In vitro effects of artemisinin ether, cycloquanil hydrochloride (alone and in combination with sulfadiazine), quinine sulphate, mefloquine, pyrimethamine phosphate, trifluoperazine and verampil on Toxoplasmosis gondii. Anti- microbial Agents and Chemotherapy 1994;38(6):1392-1396.

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