Can trimethoprim (TMP)-sulfamethoxazole (SMX) be prescribed in children?

Trimethoprim-Sulfamethoxazole Use in Children

Trimethoprim-sulfamethoxazole (TMP-SMX) can be safely prescribed in children aged 2 months and older, but is contraindicated in infants younger than 2 months due to the risk of kernicterus. 1, 2

Age-Based Considerations

• Contraindicated in infants < 2 months of age due to risk of kernicterus and immature drug metabolism 1
• Safe for children ≥ 2 months of age with appropriate dosing and monitoring 3

Dosing Guidelines

Treatment Dosing

• For most infections: 8-12 mg/kg/day of TMP component (40-60 mg/kg/day of SMX) divided into 2 doses 2
• For Pneumocystis jiroveci pneumonia (PCP):
  • 15-20 mg/kg/day of TMP component (75-100 mg/kg/day of SMX) divided into 3-4 doses 3
  • Can be administered intravenously initially, then switched to oral when clinically improved 3

Prophylaxis Dosing

• For PCP prophylaxis: 150 mg TMP with 750 mg SMX/m² divided, given 3 days per week 3
• Total daily dose should not exceed 320 mg TMP with 1600 mg SMX 3

Indications in Children

TMP-SMX is FDA-approved for pediatric use in:

• Urinary tract infections
• Acute otitis media
• Shigellosis
• Pneumocystis jiroveci pneumonia (treatment and prophylaxis) 1, 4

Monitoring Requirements

• Complete blood count with differential and platelet count at initiation and monthly during therapy 3
• Monitor for skin rashes or signs of hypersensitivity 2
• Ensure adequate hydration to prevent crystalluria 2
• For long-term use, monitor liver and renal function periodically

Adverse Effects

The overall frequency of adverse reactions appears to be lower in HIV-infected children than adults, with approximately 15% experiencing substantial adverse reactions 3.

Common adverse effects include:

• Gastrointestinal symptoms (nausea, vomiting, diarrhea)
• Skin rashes (including erythema multiforme)
• Hematologic abnormalities (neutropenia, thrombocytopenia) 3, 2

Rare but serious adverse effects:

• Stevens-Johnson syndrome
• Toxic epidermal necrolysis
• Agranulocytosis
• Aplastic anemia
• Hepatic necrosis 3, 2

Management of Adverse Reactions

• For mild to moderate skin rash: temporarily discontinue TMP-SMX and restart when rash resolves 3
• For urticarial rash or Stevens-Johnson syndrome: permanently discontinue TMP-SMX 3
• For other potentially drug-related reactions: temporarily discontinue and try again within 2 weeks 3

Alternative Medications

If TMP-SMX is not tolerated, consider:

• For children ≥5 years: aerosolized pentamidine (for PCP prophylaxis) 3
• Dapsone (1 mg/kg/day, not to exceed 100 mg/day) 3
• For severe infections requiring IV therapy: pentamidine isethionate (4 mg/kg/day) 3

Special Considerations

• Use with caution in patients with G6PD deficiency (risk of hemolytic anemia) 3
• Adjust dosage in renal impairment: reduce to half the usual dosage for creatinine clearance 15-30 mL/min, and avoid if <15 mL/min 2
• Can be administered with food to decrease gastrointestinal side effects 2
• Liquid formulation should be shaken well before measuring 2

TMP-SMX remains a valuable antibiotic for pediatric use when prescribed appropriately with attention to age restrictions, proper dosing, and monitoring for adverse effects.