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Author: Admin | 2025-04-28
And other antibacterials, use only for treatment or prevention of infections proven or strongly suspected to be caused by susceptible bacteria.When selecting or modifying anti-infective therapy, use results of culture and in vitro susceptibility testing.Because S. pyogenes (group A β-hemolytic streptococci) may not be eradicated by co-trimoxazole, do not use the drug for treatment of infections caused by this organism since it cannot prevent sequelae such as rheumatic fever. Specific PopulationsPregnancyCategory C. Because sulfonamides may cause kernicterus in neonates, co-trimoxazole is contraindicated in pregnant women at term. LactationBoth sulfamethoxazole and trimethoprim distributed into milk. Co-trimoxazole contraindicated in nursing women. Pediatric UseSafety and efficacy not established in children Geriatric UseGeriatric patients may be at increased risk of severe adverse reactions, particularly if they have impaired hepatic and/or renal function or are receiving concomitant drug therapy. The most frequent adverse reactions in geriatric patients are severe skin reactions, generalized bone marrow suppression, or a specific decrease in platelets (with or without purpura). Those receiving concurrent therapy with a diuretic (principally thiazides) are at increased risk of thrombocytopenia with purpura. Dosage adjustments are necessary based on age-related decreases in renal function.Hepatic ImpairmentUse with caution in patients with impaired hepatic function. Renal ImpairmentUse reduced dosage in patients with Clcr 15–30 mL/minute. Do not use in patients with Clcr Common Adverse EffectsGI effects (nausea, vomiting, anorexia); dermatologic and sensitivity reactions (rash, urticaria). Drug InteractionsSpecific Drugs and Laboratory TestsDrug or TestInteractionCommentsAmantadineToxic delirium reported in an individual who received amantadine and co-trimoxazole concomitantlyAntidepressants, tricyclicsPossible decreased efficacy of the tricyclic antidepressantCyclosporineReversible nephrotoxicity reported in renal transplant recipients receiving cyclosporine and co-trimoxazole concomitantlyDigoxinPossible increased digoxin concentrations, especially in geriatric patientsMonitor serum digoxin concentrations in patients receiving co-trimoxazole concomitantlyDiureticsPossible increased incidence of thrombocytopenia and purpura if certain diuretics (principally thiazides) are used concomitantly, especially in geriatric patients Hypoglycemic agents, oralPossible potentiation of hypoglycemic effectsIndomethacinPossible increased sulfamethoxazole concentrationsMethotrexateCo-trimoxazole can displace methotrexate from plasma protein-binding sites resulting in increased free methotrexate concentrations Possible interference with serum methotrexate assays if competitive protein binding technique is used with a bacterial dihydrofolate reductase as the binding protein; interference does not occur if methotrexate is measured using radioimmunoassay Use caution if methotrexate and co-trimoxazole used concomitantlyPhenytoinCo-trimoxazole may inhibit metabolism and increase half-life of phenytoin Monitor for possible increased phenytoin effects PyrimethamineMegaloblastic anemia reported when co-trimoxazole used concomitantly with pyrimethamine dosages >25 mg weekly (for malaria prophylaxis)Tests for creatininePossible interference with Jaffe alkaline picrate assay resulting in falsely elevated creatinine concentrations WarfarinPossible inhibition of warfarin clearance and prolonged PT Monitor PT closely and adjust warfarin dosage if co-trimoxazole used concomitantly Co-trimoxazole PharmacokineticsAbsorptionBioavailabilitySulfamethoxazole and trimethoprim are rapidly and well absorbed from the GI tract following oral administration of the fixed combination preparation (co-trimoxazole). Peak serum concentrations of both sulfamethoxazole and trimethoprim are attained within 1–4 hours. Co-trimoxazole contains a 1:5 ratio of trimethoprim to sulfamethoxazole, but the trimethoprim:sulfamethoxazole ratio in serum after administration of the fixed-combination preparation is about 1:20 at steady-state.DistributionExtentWidely distributed into body tissues and fluids, including sputum, aqueous humor, middle ear fluid, bronchial secretions, prostatic
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