Description
Pyrimethamine is a diaminopyrimidine which is structurally related to trimethoprim. It is effective against erythrocytic stage of Plasmodium (P) falciparum and less so against P. vivax, P. ovale and P. malariae. Pyrimethamine also inhibits the sporogony in the mosquito, resulting in a decrease of transmission of the infection within the community .

The mechanism of action of pyrimethamine is related to its inhibition of dihydrofolic reductase necessary for the folic acid synthesis in the parasite. Pyrimethamine acts slowly and is not recommended as monotherapy for acute malaria attacks. Resistance to pyrimethamine developed soon when the drug was used on a large scale as monoprophylaxis . In resistant strains, the enzyme dihydrofolic reductase binds to pyrimethamine several hundred times less than in sensitive strains . This high grade resistance is probably a onestep mutation and cannot be overcome by increasing the dose. However, when combined with long-acting sulphonomides (sulphadoxine), the effect of pyrimethamine is potentiated and the risk of developing resistant strains is far less.

Function
Used for pesticides and reagents for analysis.

Used as strong basic catalyst, ethoxylating agent and as reductant for organic synthesis, pharmaceutical synthesis, etc.

Used in medicine industry, such as phenylbutazone, methyldopa, hydrochloride, aminopterin, pyrimethamine, pifu ampicillin and so on.