Describe the mechanism of action.
Competitive antagonist of para-aminobenzoic acid (PABA) for dihydropteroate synthetase → inhibition of dihydrofolic acid synthesis
Bacteriostatic and weakly bactericidal effect [85]
Structurally different from sulfonamides but a similar mechanism of action
Describe the route of elimination.
mostly renal
Describe the clinical uses.
M. leprae: lepromatous and tuberculoid leprosy
P. jiroveci pneumonia
Prophylaxis
Treatment: used in combination with TMP as an alternative to TMP/SMX
Dermatitis herpetiformis
Alternative to the combination of sulfadiazine and pyrimethamine for toxoplasmosis
In combination with pyrimethamine as an alternative for chloroquine-resistant malaria
List adverse effects, contraindications and mechanisms of resistance.
Adverse effects
Methemoglobinemia
Triggers hemolytic anemia in patients with G6PD deficiency
Agranulocytosis
GI upset
Peripheral neuropathy
Contraindications
G6PD deficiency
Consider use in pregnant and breastfeeding women only if benefits outweigh the risks
Cautious use in patients with renal and/or hepatic dysfunction
Mechanism of resistance: mutations of folP1 gene coding for dihydropteroate synthase
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