Use of rifabutin in combination with atovaquone, clindamycin, pyrimethamine, or sulfadiazine for treatment of toxoplasmic encephalitis in mice

The effectiveness of combinations of rifabutin with atovaquone, clindamycin, pyrimethamine, or sulfadiazine in the treatment of toxoplasmic encephalitis in a murine model was investigated. Doses of each drug that were not effective in reducing inflammation in the brain of mice with toxoplasmic encephalitis when used alone were used in combination with a dose of rifabutin which was minimally effective. At the end of each period of therapy (15 or 30 days), brains of mice were examined histopathologically and the severity of the inflammatory lesions scored. Treatment with rifabutin in combination with pyrimethamine or sulfadiazine did not reduce brain inflammation significantly when compared to treatment with each drug alone. In contrast, treatment with rifabutin plus atovaquone for 15 or 30 days or with rifabutin plus clindamycin for 15 days resulted in statistically significant reduction in the inflammation. These results suggest that combining rifabutin with certain drugs that are active against Toxoplasma gondii may be useful for the treatment of toxoplasmic encephalitis in humans and may allow for a reduction in dosage of either or both drugs with a resulting reduction in untoward side effects.