Sulfamethoxazole

26 interactions 1 explained in plain English

Also sold as: Sustain

Medically reviewed by Dr. Brian Staiger, PharmD, BCPS · Updated Jul 4, 2026 · Editorial policy · Data sources

Sources: FDA prescribing information (Structured Product Labeling), the published literature cited in each entry, DDInter 2.0 (a major open-access drug-interaction database), and legacy DrugBank interaction data distributed by the NIH's RxNav service (decommissioned in 2024) — analyzed and reviewed by our pharmacist team. How we build this library →

Most serious with: Dofetilide Amitriptyline Arsenic Trioxide Methotrexate Leucovorin Injection Cyclosporine Injection

1 Contraindicated 22 Major 3 Moderate

All (26) Contraindicated (1) Major (22) Moderate (3)

Contraindicated

Sulfamethoxazole Dofetilide Tikosyn Increased dofetilide exposure and an increased risk of QT interval prolongation, and an increased risk of torsades de pointes Details

Major

Sulfamethoxazole Amitriptyline Elavil Explained An increased risk of cardiotoxicity (QT prolongation, torsades de pointes, cardiac arrest) Details Sulfamethoxazole Arsenic Trioxide Trisenox Cardiotoxicity (QT prolongation, torsades de pointes, cardiac arrest) Details Sulfamethoxazole Arsenic Trioxide Injection Trisenox Cardiotoxicity (QT prolongation, torsades de pointes, cardiac arrest) Details Sulfamethoxazole Azathioprine Azasan Increased risk of bone marrow suppression and an increased risk of myelosuppression Details Sulfamethoxazole Chloroquine Aralen® Increased risk of cardiotoxicity (QT prolongation, torsades de pointes, cardiac arrest) Details Sulfamethoxazole Cyclosporine Injection Atopica Increased nephrotoxicity and an increased risk of renal dysfunction Details Sulfamethoxazole Cyclosporine Ophthalmic Cequa Increased nephrotoxicity and an increased risk of renal dysfunction Details Sulfamethoxazole Disopyramide Norpace An increased risk of cardiotoxicity (QT prolongation, torsades de pointes, cardiac arrest) Details Sulfamethoxazole Dolasetron Anzemet An increased risk of cardiotoxicity (QT prolongation, torsades de pointes, cardiac arrest) Details Sulfamethoxazole Dolasetron Injection Anzemet An increased risk of cardiotoxicity (QT prolongation, torsades de pointes, cardiac arrest) Details Sulfamethoxazole Exenatide Injection Bydureon Reduced oral antibiotics absorption and reduced efficacy of oral antibiotics Details Sulfamethoxazole Flecainide Tambocor® An increased risk of cardiotoxicity (QT prolongation, torsades de pointes, cardiac arrest) Details Sulfamethoxazole Foscarnet Injection Foscavir An increased risk of cardiotoxicity (QT prolongation, torsades de pointes, cardiac arrest) Details Sulfamethoxazole Isradipine DynaCirc® An increased risk of cardiotoxicity (QT prolongation, torsades de pointes, cardiac arrest) Details Sulfamethoxazole Leucovorin Vykoura Reduced efficacy of trimethoprim/sulfamethoxazole Details Sulfamethoxazole Leucovorin Injection Vykoura Reduced efficacy of trimethoprim/sulfamethoxazole Details Sulfamethoxazole Mefloquine Lariam® An increased risk of cardiotoxicity (QT prolongation, torsades de pointes, cardiac arrest) Details Sulfamethoxazole Mercaptopurine Purinethol® Increased risk of bone marrow suppression and an increased risk of myelosuppression Details Sulfamethoxazole Methotrexate Jylamvo An increased methotrexate exposure, an increased risk of methotrexate toxicity or methotrexate-related severe adverse reactions, r... Details Sulfamethoxazole Methotrexate Injection Abitrexate® An increased methotrexate exposure, an increased risk of methotrexate toxicity or methotrexate-related severe adverse reactions, r... Details Sulfamethoxazole Octreotide Bynfezia An increased risk of cardiotoxicity (QT prolongation, torsades de pointes, cardiac arrest) Details Sulfamethoxazole Octreotide Injection Bynfezia An increased risk of cardiotoxicity (QT prolongation, torsades de pointes, cardiac arrest) Details

Moderate

Sulfamethoxazole Chloroprocaine Antagonism of the sulfonamide's antibacterial effect Details Sulfamethoxazole Didanosine Videx® Reduced sulfamethoxazole exposure Details Sulfamethoxazole Lixisenatide Injection Adlyxin® Delayed therapeutic effect Details

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