Complex sentence: Proguanil (proguanil hydrochloride) is a prophylactic antimalarial drug, which works by stopping the malaria parasite, "Plasmodium falciparum" and Plasmodium vivax, from reproducing once it is in the red blood cells.
Split into simpler sentences: Proguanil (proguanil hydrochloride) is a prophylactic antimalarial drug. It works by stopping the malaria parasite, "Plasmodium falciparum" and Plasmodium vivax, from reproducing once it is in the red blood cells.