title: In vitro susceptibility of Plasmodium falciparum malaria to pyrimethamine, sulfadoxine, trimethoprim and sulfamethoxazole, singly and in combination.
abstract: Two isolates of Plasmodium falciparum (F 32 and K 1) were tested against sulfadoxine (SDX), sulfamethoxazole (SMZ), pyrimethamine (PYR) and trimethoprim (TMP), using a 48 h microtest, with RPMI-1640 low in PABA and folic acid. The IC50 for F 32 was: PYR 6.1 X 10(-9) M (mol/litre), TMP 1.3 X 10(-7) M, Fansidar (SDX/PYR 80:1) less than 10(-8) to 1.3 X 10(-10) M and cotrimoxazole (SMZ/TMP 20:1) 2.6 X 10(-7) to 1.3 X 10(-8) M. The IC50 for K 1 was: PYR greater than 10(-6) M, TMP 8.2 X 10(-7) M, Fansidar 4.1 X 10(-7) to 1.1 X 10(-9) M and cotrimoxazole 1.8 X 10(-6) to 9.0 X 10(-8) M. The difference in IC50 between F 32 and K 1 against TMP and cotrimoxazole is much less than the difference between the IC50 values against PYR and Fansidar, indicating that cross-resistance between PYR and TMP exists, but is not complete. A method for calculating the IC50 by linear regression analysis is described.
authors.forename: E
authors.initials: E
authors.lastname: Petersen
mesh_terms: D000818:Animals; D000962:Antimalarials / Q000494:pharmacology; D004338:Drug Combinations / Q000494:pharmacology; D004357:Drug Synergism; D010963:Plasmodium falciparum / Q000187:drug effects*; D011739:Pyrimethamine / Q000494:pharmacology*; D013413:Sulfadoxine / Q000494:pharmacology*; D013420:Sulfamethoxazole / Q000494:pharmacology*; D013424:Sulfanilamides / Q000494:pharmacology*; D014295:Trimethoprim / Q000494:pharmacology*; D015662:Trimethoprim, Sulfamethoxazole Drug Combination
chemical_list: D000962:Antimalarials; D004338:Drug Combinations; D013424:Sulfanilamides; C001205:fanasil, pyrimethamine drug combination; D015662:Trimethoprim, Sulfamethoxazole Drug Combination; D013413:Sulfadoxine; D014295:Trimethoprim; D013420:Sulfamethoxazole; D011739:Pyrimethamine