Pyrimethamine+ sulfadoxine, prevention malaria

In many areas, resistance to folate antagonists and sulfonamides is common for P falciparum and less common for P vlvax. Resistance is due primarily to mutations in dihydrofolate reductase and dihydropteroate synthase, with increasing numbers of mutations leading to increasing levels of resistance. At present, resistance seriously limits the efficacy of sulfadoxine-pyrimethamine (Fansidar) for the treatment of malaria in most areas, but in Africa most parasites exhibit only moderate resistance, such that antifolates appear to continue to offer preventive efficacy against malaria. Because different mutations may mediate resistance to different agents, cross-resistance is not uniformly seen. 

In addition, sulfadoxine and pyrimethamine (Fansidar) are indicated in prophylaxis of malaria in individuals traveling to areas where chloroquine-resistant P. falciparum malaria is endemic. However, resistant strains may be encountered. Regardless of the prophylactic regimen used, it is still possible to contract malaria. Moreover, this combination has been used as a prophylactic agent in the prevention of Pneumocystis carinii pneumonia in patients with AIDS. 

Sulfadoxine (1500 mg) and pyrimethamine (75 mg) orally as a single dosage is indicated for the treatment of P. falciparum malaria in patients in whom chloroquine resistance is suspected. However, chloroquine remains the drug of choice for travelers to malarious areas, hi addition, sulfadoxine-pyrimethamine has been used as a prophylactic agent for the prevention of Pneumocystis carinii pneumonia in patients with AIDS, usually as a second-tine agent. 

---