Volume 33, Issue 3
  • ISSN: 0002-9637
  • E-ISSN: 1476-1645



Two strains of were tested in vitro for sensitivity to the dihydrofolate reductase inhibitor pyrimethamine, the -aminobenzoic acid (PABA) analogue sulfadoxine, and combinations of both drugs. One strain was sensitive and one resistant to pyrimethamine in vitro. Parasites cultured in medium containing neither folic acid nor PABA were inhibited by 10 M sulfadoxine, a concentration well below that achievable after therapeutic dosage. Folic acid added to this medium at a physiological concentration of 0.01 mg/liter caused a 1,000-fold reduction in sulfadoxine activity; a 100-fold higher concentration of folic acid caused a 10-fold reduction in pyrimethamine activity. Sulfadoxine in a concentration of 10 M was able to potentiate pyrimethymine activity in PABA-free medium with no added folic acid or with 0.01 mg folic acid/liter. These data indicate that can utilize exogenous folic acid, and suggest that sulfadoxine may potentiate pyrimethamine activity by simultaneous inhibition of dihydrofolate reductase.


Article metrics loading...

The graphs shown below represent data from March 2017
Loading full text...

Full text loading...


Most Cited This Month

This is a required field
Please enter a valid email address
Approval was a Success
Invalid data
An Error Occurred
Approval was partially successful, following selected items could not be processed due to error