ANN ARBOR--For many AIDS patients, treating a common type of pneumonia is problematic because they are allergic to the antibiotic proven to be most successful at fighting the infection. Now, researchers are reporting a breakthrough in helping those patients tolerate the medication.
In the longest running trial of its kind, doctors from the University of Michigan Medical Center and Brigham and Women's Hospital in Boston found that 86 percent of their HIV study patients were able to tolerate trimethoprim-sulfamethoxazole (also called Bactrim) after a previous allergic reaction. The results are reported in the November issue of the journal Allergy, Asthma and Immunology.
Bactrim is considered by the Centers for Disease Control to be the medication of choice in treating pneumocystis carinii pneumonia. However, there is a high incidence of fever and rash that forces up to a third of the patients to stop taking the drug.
The research team, headed by Powel Kazanjian, M.D., associate professor of internal medicine at the U-M Medical Center, designed a daily regimen of stepped-up dosages of Bactrim over an eight-day period. Patients were given incrementally larger oral doses over the eight days, ending up with a standard dose on day eight.
Kazanjian and his colleagues found that 86 percent of the HIV study patients were able to tolerate Bactrim after the eight-day regimen. Sixty percent tolerated the stepped-up dosages without problem. Another 26 percent were able to successfully take Bactrim, combined with a small dose of prednisone. The remaining study patients were forced to discontinue the program because of allergic reactions, none of which were life-threatening.
Kazanjian, who is director of the HIV/AIDS Program at U-M, says previous attempts to desensitize HIV patients have reported similar efficacies, but this study differs because patients were followed over a much longer period of time. Of the 19 patients who were successfully desensitized, 12 were still taking the medication without reaction nearly two years later. Six others had died and one patient had to discontinue because of another illness.
Attempts to determine the mechanism of desensitization were unsuccessful. Despite this, Kazanjian says the importance lies in the successful long-term desensitization of a vast majority of the patients previously allergic to Bactrim. "It's quite important," he says, "because we can now avoid having to give multiple medications, which avoids toxicity of drug interactions and it's much less costly."
The most common alternate method of preventing pneumocystis carinii is called aerosolized pentamidine. Kazanjian says this regimen is much more expensive than treatment with Bactrim and requires the HIV patient to come into the health care setting more often. Patients taking Bactrim, on the other hand, can be treated on an outpatient basis and the cost is significantly lower.
"I think that when a person has HIV and their immunity begins to wane, leaving them at risk of opportunistic infections, keeping them on Bactrim is one of the most important methods of keeping them from getting infections, "Kazanjian says. "This regimen allows that to occur."
Patients taking Bactrim do so at home. The dosages are administered orally by squirting a syringe into the mouth. Kazanjian says the desensitization regimen is now used as a part of standard clinical treatment for HIV patients with specific infections.