Clinical pharmacology of atovaquone and proguanil hydrochloride

Abstract

Background: Atovaquone and proguanil hydrochloride is a new antimalarial combination that is used for treatment and prophylaxis of malaria. Methods: The clinical pharmacology of atovaquone and proguanil was reviewed. Results: Atovaquone is a highly lipophilic compound with low aqueous solubility, the absorption of which is limited by the rate and extent of dissolution. Dietary fat increases the rate and extent of atovaquone absorption, increasing AUC two- to threefold and C(max) fivefold over fasting. Proguanil is rapidly and extensively absorbed regardless of food intake. Atovaquone is highly protein bound (> 99%) but does not displace other highly protein bound drugs in vitro, indicating significant drug interactions arising from displacement are unlikely. Atovaquone is predominantly eliminated unchanged in feces, with negligible excretion in urine. Proguanil is partially metabolized and partially excreted unchanged in urine. Its principal metabolite, cycloguanil, is also excreted in urine. Metabolism of proguanil is mediated in the liver by the cytochrome P450 3A and 2C subfamilies. The elimination half-life of atovaquone is 2 to 3 days in adults and 1 to 2 days in children. The elimination half-lives of proguanil and cycloguanil are 12 to 15 hours in adults and children. Dosage adjustments based on body weight categories in children (1/4 dose for 11-20 kg, 1/2 dose for >20-30 kg, 3/4 dose for >30-40 kg, and full dose for >40 kg) achieve plasma concentrations that are safe and effective during prophylaxis and treatment of malaria. No dose adjustments for race, proguanil metabolizer status, gender, or elderly patients are needed, or for patients with mild to moderately impaired renal or hepatic function. Conclusion: The clinical pharmacology of atovaquone and proguanil provides a rationale for the dosing regimens recommended for treatment and prophylaxis of malaria.