Anti-malarial tablets. Blister pack of Malarone, an anti-malarial drug. Malaria is caused by the parasite Plasmodium sp., which is carried around by mosquitoes (Anopheles sp.) and injected into a person's bloodstream via a mosquito bite. Malarone is a combination drug, each tablet containing 250 milligrams of atovaquone and 100 milligrams of proguanil hydrochloride. The two active ingredients prevent the parasite Plasmodium falciparum, which causes the most serious form of malaria, malignant malaria, from reproducing in the bloodstream. Higher doses of the two active ingredients can also be used to treat uncomplicated malaria.