Sulfamethizole has 5 known drug interactions based on U.S. FDA drug labeling data. Of these, 1 are contraindicated combinations that should be avoided entirely. Notable interactions include combinations with Methenamine Mandelate, Fosphenytoin Sodium, Methenamine Hippurate. Patients taking Sulfamethizole should inform their healthcare provider of all current medications — including over-the-counter drugs and supplements — to avoid potentially harmful combinations. Data sourced from OpenFDA and the NIH National Library of Medicine.
- Total
- 5
- Contraindicated
- 1
- Moderate
- 4
Contraindicated (1)
- Sulfamethizole + Methenamine Mandelate— Formaldehyde and sulfamethizole form an insoluble precipitate in acid urine; concurrent use should not occur.
Moderate (4)
- Sulfamethizole + Fosphenytoin Sodium— May increase phenytoin serum levels; monitoring of phenytoin levels recommended.
- Sulfamethizole + Methenamine Hippurate— Concomitant administration may result in precipitate formation in the urine.
- Sulfamethizole + Phenytoin— May increase phenytoin serum levels; monitoring of phenytoin levels recommended.
- Sulfamethizole + Phenytoin Sodium— May increase phenytoin serum levels; monitoring of phenytoin levels recommended.