What is the recommended Bactrim (trimethoprim/sulfamethoxazole) dosing for a 27 kg patient?

Trimethoprim/Sulfamethoxazole (Bactrim) Dosing for a 27 kg Child

For a 27 kg child, the recommended Bactrim dosage is 8-12 mg/kg/day of the trimethoprim component, divided into 2 doses given every 12 hours, which equates to approximately 108-162 mg of trimethoprim per day (54-81 mg twice daily).

Dosage Calculation

The FDA-approved dosing for children with trimethoprim-sulfamethoxazole is based on the trimethoprim component:

• Standard pediatric dosing: 8 mg/kg/day of trimethoprim component divided into 2 doses 1
• For a 27 kg child:
  • 8 mg/kg/day × 27 kg = 216 mg/day of trimethoprim
  • Divided into 2 doses = 108 mg (trimethoprim) twice daily

Practical Administration

Based on available formulations:

• Oral suspension (40 mg trimethoprim/200 mg sulfamethoxazole per 5 mL):
  • 13.5 mL twice daily
• Tablets (80 mg trimethoprim/400 mg sulfamethoxazole):
  • 1 tablet twice daily (slightly lower than calculated dose but within therapeutic range)

Indications and Duration

Duration depends on the condition being treated:

• Urinary tract infections: 10-14 days 1
• Acute otitis media: 10 days 1
• Shigellosis: 5 days 1

Special Considerations

Contraindications

• Contraindicated in children less than 2 months of age due to risk of kernicterus 1, 2
• Hypersensitivity to trimethoprim or sulfonamides 2

Renal Impairment

• For creatinine clearance 15-30 mL/min: reduce to half the usual dosage
• For creatinine clearance <15 mL/min: not recommended 1

Administration Tips

• Shake liquid formulation well before measuring
• Administer with food to decrease GI side effects
• Ensure adequate hydration during therapy 3
• Can mix with small amount of juice if taste is not tolerated 3

Monitoring and Adverse Effects

Common adverse effects include:

• Gastrointestinal symptoms (nausea, vomiting, diarrhea)
• Hypersensitivity reactions (rash)

Rare but serious adverse effects:

• Stevens-Johnson syndrome
• Blood dyscrasias
• Hepatic necrosis 2, 3

Monitor for:

• Skin rashes or other signs of hypersensitivity
• Adequate hydration to prevent crystalluria 2

Alternative Agents

If trimethoprim-sulfamethoxazole is contraindicated or not tolerated, consider alternative antimicrobials based on the specific infection being treated and local susceptibility patterns.

Remember to adjust the dose as the child grows, as pediatric dosing is weight-based.