Take the tablet orally with a glass of water, with or without food. Taking it with food or milk may help to minimize gastrointestinal upset. Drink plenty of fluids to prevent crystalluria.

Sulfamethoxazole inhibits bacterial dihydropteroate synthase, an enzyme involved in bacterial folic acid synthesis. Trimethoprim inhibits bacterial dihydrofolate reductase, an enzyme involved in the next step of folic acid synthesis. This sequential blockade provides a synergistic bactericidal effect.

• •Hypersensitivity to sulfamethoxazole, trimethoprim, or any component of the formulation
• •Megaloblastic anemia due to folate deficiency
• •Severe renal impairment (creatinine clearance < 15 mL/min) not on dialysis
• •Severe hepatic impairment
• •Infants less than 2 months of age
• •Pregnancy at term and during lactation (due to risk of kernicterus)

Store in a cool, dry place, below 30°C. Protect from light and moisture. Keep out of reach of children.

Symptoms of acute overdose include nausea, vomiting, dizziness, headache, crystalluria, hematuria, and depression of bone marrow. Chronic overdose can lead to bone marrow suppression. Treatment is symptomatic and supportive, including gastric lavage, forced diuresis, alkalinization of urine, and possibly hemodialysis for severe cases.

Pregnancy Category C/D (depending on trimester). Avoid in late pregnancy due to the risk of kernicterus in the neonate. Use only if the potential benefit justifies the potential risk to the fetus. Excreted in breast milk; generally avoided during lactation, especially in premature or jaundiced infants, or infants with G6PD deficiency, due to kernicterus risk.