Pyrimethamine là một di-aminopyrimidine ngăn chặn tổng hợp axit nucleic trong ký sinh trùng sốt rét. Nó cũng cản trở quá trình trao đổi chất folate. Nó được phát triển trong năm 1951 và vẫn còn được sử dụng rộng rãi trong điều trị của bệnh toxoplasmosis (lịch sử tự nhiên trong số đó là tóm tắt ngắn gọn trong các chuyên khảo về spiramycin) | PYRIMETHAMINE Use Pyrimethamine is used with sulfadiazine . to treat toxoplasmosis and with sulfadoxine to treat malaria as an alternative to co-trimoxazole . in areas where resistance has not yet developed. Pharmacology Pyrimethamine is a di-aminopyrimidine that blocks nucleic acid synthesis in the malaria parasite. It also interferes with folate metabolism. It was developed in 1951 and is still widely used in the treatment of toxoplasmosis the natural history of which is briefly summarised in the monograph on spiramycin although the only proof of efficacy comes from trials in patients where toxoplasmosis was a complication of HIV infection. Prolonged administration can depress haemopoeisis. Other side effects are rare but skin rashes may occur and high doses can cause atrophic glossitis and megaloblastic anaemia. Folinic acid the 5-formyl derivative of folic acid is used to prevent this during pregnancy because folinic acid does not interfere with the impact of pyrimethamine on malaria and toxoplasma parasites. Pyrimethamine is well absorbed by mouth and slowly excreted by the kidney the average plasma half life being about 4 days. Tissue levels exceed plasma levels VD 3 l kg . The efficacy of pyrimethamine in treating toxoplasmosis is increased eight fold by sulfadiazine. Other sulphonamides are not as effective. Efficacy in treating malaria is also improved by giving sulfadoxine. For this reason a sulphonamide should always be prescribed when pyrimethamine is used to treat a baby for malaria or toxoplasmosis unless there is significant neonatal jaundice even though the manufacturer only endorses such use in children over five years old. Long term administration can sometimes cause problems as outlined in the monograph on sulfadiazine . Lactation should not be discouraged during treatment although the baby probably receives about a third of the maternal dose on a weight-for-weight basis. Intermittent prophylactic use where malaria is endemic See the web .
