Proguanil is a biguanide derivative which is active against several protozoal species and is used in combination with atovaquone and chloroquine for the prevention and therapy of malaria. Proguanil has not been evaluated extensively as a single agent, but the combinations of proguanil with atovaquone or chloroquine have been used to treat malaria and have been linked to serum enzyme elevations during therapy and rare instances of clinically apparent acute liver injury.