Antiparasitic Drugs - Anti Malarials

Malaria: P. vivax (fever spike every 24-48 hrs), falciparum (irregular fever spike pattern, blood stage only), malariae (fever spike every 4th day), ovale.

• Stages – primary stage in liver for all four species; secondary stage is either erythrocytic (P. falciparum) or extraerythrocytic (stay in liver, other 3 species).

• MOA of drugs – affect DNA synthesis or folic acid metabolism

Erythrocytic drugs effective against P. falciparum: Chloroquine, mefloquine, quinine

1. Chloroquine – Inhibits DNA synthesis; effective against P. falciparum blood form; ocular and cardiac toxicities; hemolytic anemia in G6PDH deficient individuals; cures P. falciparum but has no effect on relapsing malarias (Pp. malariae, ovale, vivax); take once a week for two weeks before trip and six weeks after leaving.

2. Mefloquine – Like chloroquine; can also be used prophylatically; contraindicated in epilepsy, psychiatric disorders, cardiac problems, and pregnancy.

3. Quinine – Effective against P. falciparum; inhibits DNA synthesis; cinchoism (ototoxicity, GI toxicity, visual toxicity); blackwater fever; hemolytic anemia in G6PDH deficient; used in combination with pyrimethamine or sulfadiazine.

Extraerythrocytic drugs effective against PP. vivax, ovale, malariae: Primaquine

1. Primaquine – Affects DNA synthesis in liver tissue; also inhibits electron transport; hemolytic anemia in G6PDH deficient; methemoglobinemia; radical cure of vivax, ovale, malariae.

Drugs useful in both stages: Pyrethamine, trimethoprimm sulfones, sulfonamides – All are folic acid inhibitors that act slowly (as opposed to above listed drugs, which act quickly).

Category: Pharmacology Notes