proguanil

proguanil is an antimalarial medication belonging to the class of biguanides. It is primarily used for the chemoprophylaxis of malaria, particularly in combination with atovaquone in the widely used formulation Malarone. The drug requires metabolic activation in the human liver by the enzyme CYP2C19 to become its active form, cycloguanil, which inhibits the parasitic enzyme dihydrofolate reductase.

Medical uses

Proguanil is indicated for the prevention of malaria caused by Plasmodium falciparum, especially in areas with known chloroquine resistance. It is almost exclusively used in combination with atovaquone, as the fixed-dose combination Malarone, which is marketed by GlaxoSmithKline. This combination is recommended by the World Health Organization and the Centers for Disease Control and Prevention for travelers to endemic regions. It is generally not used as a standalone treatment for acute malaria infection, a role more commonly filled by artemisinin-based combination therapies. The medication is also sometimes used off-label in combination with chloroquine in certain regions, though this practice has declined.

Adverse effects

Common adverse effects of proguanil include mild gastrointestinal disturbances such as nausea, abdominal pain, and diarrhea. Mouth ulcers and hair loss have been reported infrequently. Serious adverse effects are rare but can include severe skin reactions like Stevens-Johnson syndrome. A significant safety consideration is that proguanil can potentiate the anticoagulant effect of warfarin, necessitating careful monitoring of International Normalized Ratio levels. The U.S. Food and Drug Administration advises caution in patients with severe renal impairment, as the drug is excreted renally.

Pharmacology

Proguanil is a prodrug that is metabolized primarily in the liver by the cytochrome P450 enzyme CYP2C19 into its active triazine metabolite, cycloguanil. Cycloguanil acts as a competitive inhibitor of the parasite enzyme dihydrofolate reductase, thereby disrupting the synthesis of tetrahydrofolate and halting DNA replication in the Plasmodium species. Its mechanism is similar to that of pyrimethamine, but it is a distinct chemical entity. Pharmacokinetic studies show proguanil has a half-life of approximately 12-21 hours, and its absorption is not significantly affected by food.

History

Proguanil was discovered during the massive antimalarial research programs of World War II, a period that also yielded chloroquine and primaquine. It was first synthesized in 1945 by scientists at the British firm Imperial Chemical Industries led by Frank Leonard Rose. The drug was introduced for medical use in 1948 under the brand name Paludrine and represented a significant advance in malaria chemoprophylaxis. Its role evolved over the latter half of the 20th century, particularly after the development of widespread resistance to chloroquine in regions like Southeast Asia and Sub-Saharan Africa.

Society and culture

Proguanil, especially as a component of Malarone, is a mainstay of malaria prevention for travelers from non-endemic countries and is frequently stocked by travel clinics associated with organizations like the International Society of Travel Medicine. It is on the World Health Organization's List of Essential Medicines. The cost of the combination drug can be a barrier to access in some developing countries. The medication has been involved in public health initiatives led by entities such as the President's Malaria Initiative and the Global Fund to Fight AIDS, Tuberculosis and Malaria.

Category:World Health Organization essential medicines Category:Antimalarial agents