Sulfamethoxazole and Trimethoprim Suspension

Generic name: Sulfamethoxazole and Trimethoprim

Drug class: Sulfonamide Antibiotics

Dosage form: Oral Suspension

Root of administration: Oral

Dose:

• Adults: 20 mL (200 mg sulfamethoxazole and 40 mg trimethoprim) every 12 hours for 10 to 14 days for urinary tract infections; 20 mL every 12 hours for 5 days for shigellosis; 20 mL every 12 hours for 14 days for acute exacerbations of chronic bronchitis; 20 mL every 12 hours for 5 days for traveler’s diarrhea.
• Children (2 months and older): 40 mg/kg sulfamethoxazole and 8 mg/kg trimethoprim per 24 hours, divided into two doses every 12 hours for 10 days for urinary tract infections and acute otitis media; identical daily dosage for 5 days for shigellosis; 75 to 100 mg/kg sulfamethoxazole and 15 to 20 mg/kg trimethoprim per 24 hours, divided into four doses every 6 hours for 14 to 21 days for Pneumocystis jiroveci pneumonia; 750 mg/m²/day sulfamethoxazole and 150 mg/m²/day trimethoprim, divided into two doses every 12 hours for 3 consecutive days per week for prophylaxis of Pneumocystis jiroveci pneumonia.

Mechanism of action: Sulfamethoxazole inhibits bacterial synthesis of dihydrofolic acid by competing with para-aminobenzoic acid, while trimethoprim inhibits bacterial dihydrofolate reductase, leading to a sequential blockade in the folic acid pathway, essential for bacterial DNA synthesis.

Drug usage cases:

• Urinary tract infections
• Acute otitis media in children
• Shigellosis
• Acute exacerbations of chronic bronchitis in adults
• Pneumocystis jiroveci pneumonia (treatment and prophylaxis)
• Traveler’s diarrhea in adults

Drug contra indications:

• Hypersensitivity to sulfamethoxazole, trimethoprim, or other sulfonamides
• History of drug-induced immune thrombocytopenia with use of trimethoprim and/or sulfonamides
• Documented megaloblastic anemia due to folate deficiency
• Pediatric patients less than 2 months of age
• Marked hepatic damage
• Severe renal insufficiency when renal function status cannot be monitored

Side effects:

• Gastrointestinal disturbances (nausea, vomiting, diarrhea)
• Skin reactions (rash, pruritus, photosensitivity)
• Hematologic effects (leukopenia, thrombocytopenia, megaloblastic anemia)
• Elevated liver enzymes
• Hyperkalemia
• Renal impairment
• Hypoglycemia (especially in patients on concurrent sulfonylureas)
• Headache, dizziness
• Fatigue

Warnings:

• Use with caution in patients with impaired renal or hepatic function
• Monitor blood counts periodically during prolonged therapy
• Discontinue therapy if significant hematologic abnormalities occur
• Use with caution in patients with glucose-6-phosphate dehydrogenase deficiency
• May cause severe skin reactions; discontinue if signs of severe skin reactions occur
• May increase the risk of hyperkalemia; monitor potassium levels
• Use with caution in patients with a history of folate deficiency
• May interact with other medications; review patient’s medication list

Use during pregnancy or breastfeeding:

Pregnancy: Category C. Animal studies have shown adverse effects on the fetus, but there are no adequate and well-controlled studies in humans. Use only if the potential benefit justifies the potential risk to the fetus.

Breastfeeding: Sulfamethoxazole and trimethoprim are excreted in human milk. Due to the potential for serious adverse reactions in nursing infants, a decision should be made whether to discontinue nursing or discontinue the drug, taking into account the importance of the drug to the mother.