Sulfamethoxazole + trimethoprim


Generic Medicine Info
Contraindications
Hypersensitivity to sulfonamides or trimethoprim. History of drug-induced immune thrombocytopenia with sulfonamides or trimethoprim use; acute porphyria, megaloblastic anaemia due to folate deficiency. Severe hepatic parenchymal damage; severe renal insufficiency where repeated plasma concentration measurements cannot be performed. Infants <6 weeks, except for the treatment/prophylaxis of Pneuomocsytis jirovecii pneumonia in infants ≥4 weeks. Concurrent administration with dofetilide (IV).
Special Precautions
Patient with severe allergy or atopy, bronchial asthma, thyroid dysfunction, G6PD deficiency, potential folate deficiency (e.g. malnourished, receiving chronic anticonvulsant therapy), predisposition to hyperkalaemia, AIDS; serious haematologic disorder. When used for uncomplicated UTIs, avoid using the combination if a single antibacterial agent is effective. Do not use for the treatment of group A β-haemolytic streptococcal infections. Avoid use with leucovorin in the treatment of HIV patients with P. jirovecii pneumonia. Slow acetylators. Renal and mild to moderate hepatic impairment. Children and elderly. Pregnancy and lactation. Monitoring Parameters Perform culture and susceptibility tests; consult local institutional recommendations before treatment initiation due to antibiotic resistance risks. Obtain LFTs and renal function tests before initiating treatment. Monitor CBC with differential, serum K and Na, creatinine, and BUN periodically on prolonged therapy; urinalysis with microscopic exam. Closely check for signs and symptoms of skin reactions.
Adverse Reactions
Significant: Hyperkalaemia, hyponatraemia, hypoglycaemia, sulfonamide allergy, porphyria exacerbation; haemolysis (in G6PD deficient patient). Rarely, crystalluria. Gastrointestinal disorders: Nausea, diarrhoea, vomiting. General disorders and administration site conditions: Local infusion-site reaction (e.g. pain, irritation, inflammation). Infections and infestations: Fungal overgrowth. Metabolism and nutrition disorders: Anorexia. Nervous system disorders: Headache, drowsiness. Skin and subcutaneous tissue disorders: Rashes.
Potentially Fatal: Stevens-Johnson syndrome, toxic epidermal necrolysis, blood dyscrasias (e.g. agranulocytosis, aplastic anaemia), immune-mediated thrombocytopenia, cholestatic jaundice, fulminant hepatic necrosis, hypersensitivity of the respiratory tract; Clostridium difficile-associated diarrhoea, pseudomembranous colitis.
Drug Interactions
Increased risk of thrombocytopenia with or without purpura with thiazide diuretics in the elderly. May potentiate the effects of oral anticoagulants (e.g. warfarin) and phenytoin. May increase risk of nephrotoxicity with ciclosporin. May elevate the plasma levels and risk of megaloblastic anaemia of methotrexate. Sulfamethoxazole: May potentiate the effects of sulfonylureas. Trimethoprim: May increase serum concentrations of digoxin, procainamide, repaglinide, zidovudine, zalcitabine, and lamivudine. May decrease serum concentrations with rifampicin. May increase risks of megaloblastic anaemia with other folate inhibitors (e.g. pyrimethamine). May enhance the risk of hyperkalaemia with ACE inhibitors.
CIMS Class
Antibacterial Combinations
ATC Classification
J01EC01 - sulfamethoxazole ; Belongs to the class of intermediate-acting sulfonamides. Used in the systemic treatment of infections.
J01EA01 - trimethoprim ; Belongs to the class of trimethoprim and derivatives. Used in the systemic treatment of infections.
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