The recommended treatment for malaria is a combination of antimalarial medications that includes an artemisinin. Garcia believed metformin to have bacteriostatic, antiviral, antimalarial, antipyretic and analgesic actions. Recommended treatment for severe malaria is the intravenous use of antimalarial drugs. It seems still efficacious as an IV antimalarial against Plasmodium Falciparum. Sulfonamides are used to treat allergies and cough, as well as antifungal and antimalarial functions. Two main mechanisms of resistance drive "Plasmodium" resistance to antimalarial drugs. It blocks intracellular protein transport, and exhibits antibiotic, antimalarial, and other biological activities. There is some evidence for antimalarial activity for doxorubicin and similar compounds. Lumefantrine is a relative of halofantrine that is used in some combination antimalarial regimens. Treatment includes antimalarial drugs, however, resistance has been observed. Aminoquinolines are derivatives of quinoline, most notable for their roles as antimalarial drugs. Some biguanides are also used as antimalarial drugs. SHMT has also undergone investigation as a potential target for antimalarial drugs. Proguanil displays synergism when used in combination with the antimalarial atovaquone. Resistance is now common against all classes of antimalarial drugs apart from artemisinins.