What are the guidelines for using Bactrum (co-trimoxazole) in pediatric patients?

Bactrim (Co-trimoxazole) Guidelines for Pediatric Patients

Primary Recommendation

Bactrim is contraindicated in infants younger than 2 months of age and should be used cautiously in children, with amoxicillin now preferred as first-line therapy for most common pediatric infections including pneumonia. 1

Approved Pediatric Indications and Dosing

Standard Treatment Dosing (Children ≥2 months)

Urinary Tract Infections:

• 40 mg/kg sulfamethoxazole + 8 mg/kg trimethoprim per 24 hours, divided every 12 hours for 10 days 1
• Alternative: 10 mg/kg trimethoprim + 40 mg/kg sulfamethoxazole twice daily for 5 days 2

Acute Otitis Media:

• 4 mg/kg trimethoprim + 20 mg/kg sulfamethoxazole twice daily for 5 days 2
• Only recommended where there is no known resistance to co-trimoxazole 2

Shigellosis:

• Same dosing as UTI but for 5 days duration 1

Weight-Based Dosing Table

• 22 lb (10 kg): 1 tablet every 12 hours 1
• 44 lb (20 kg): 1½ tablets every 12 hours 1
• 66 lb (30 kg): 2 tablets or 1 DS tablet every 12 hours 1
• 88 lb (40 kg): 2 tablets or 1 DS tablet every 12 hours 1

Pneumocystis Jirovecii Pneumonia

Treatment:

• 75-100 mg/kg sulfamethoxazole + 15-20 mg/kg trimethoprim per 24 hours, divided every 6 hours for 14-21 days 1

Prophylaxis:

• 750 mg/m²/day sulfamethoxazole + 150 mg/m²/day trimethoprim, divided twice daily, 3 consecutive days per week 1
• Maximum daily dose: 1600 mg sulfamethoxazole + 320 mg trimethoprim 1

Long-term Prophylaxis for Recurrent UTI

• 2 mg/kg trimethoprim + 10 mg/kg sulfamethoxazole once daily 3
• Proven effective with only 6 of 130 children developing reinfection during 2637 months of treatment 3

Current Clinical Position vs. Alternative Antibiotics

Pneumonia Treatment - Major Guideline Shift

Amoxicillin is now preferred over co-trimoxazole as first-line therapy for non-severe pneumonia in children 2

Rationale for this change:

• Co-trimoxazole has higher treatment failure rates compared to amoxicillin in pneumonia 2
• Widespread bacterial resistance to co-trimoxazole limits efficacy 2
• Amoxicillin lacks anti-malarial activity, allowing concurrent malaria treatment in endemic areas 2

When co-trimoxazole was used first-line, the preferred second-line agent is oral amoxicillin at 50 mg/kg in two divided doses for 5 days 2

HIV-Infected Children - Important Exception

For children with HIV in areas of high HIV prevalence presenting with non-severe pneumonia, amoxicillin is recommended regardless of co-trimoxazole prophylaxis status 2

• Co-trimoxazole prophylaxis reduces mortality by 58% in adults starting ART 4
• Provides ongoing protection against malaria and bacterial infections after immune reconstitution 4
• WHO now recommends long-term co-trimoxazole prophylaxis for HIV-infected children in settings with high malaria or severe bacterial infection prevalence 4

Special Populations and Adjustments

Renal Impairment

• Creatinine clearance >30 mL/min: Standard dosing 1
• Creatinine clearance 15-30 mL/min: Half the usual dose 1
• Creatinine clearance <15 mL/min: Use not recommended 1

Malaria-Endemic Regions

If pneumonia cannot be distinguished from malaria, prescribe both first-line therapies for malaria AND pneumonia concurrently 2

Safety Considerations and Contraindications

Absolute Contraindications

• Infants <2 months of age 1
• Pregnancy (Category C) - may interfere with folic acid metabolism 1
• Nursing mothers - excreted in breast milk 1

Common Adverse Events (Grade 3-4)

• Urticarial rash (equally common as placebo) 5
• Neutropenia (grade 4, more common with co-trimoxazole) 5
• Anaemia (equally common as placebo) 5
• Rare but serious: toxic epidermal necrolysis 5

Monitoring Requirements

• Elderly patients and those with renal impairment require close monitoring for hyperkalemia 1
• Serum potassium monitoring warranted in patients with underlying potassium metabolism disorders 1
• Hematological changes indicating folic acid deficiency may occur, reversible with folinic acid 1

Critical Clinical Pitfalls

Resistance Patterns

Despite high levels of microbial resistance reported globally, co-trimoxazole maintains efficacy in specific contexts (HIV prophylaxis, malaria prevention) 4

However, resistance significantly impacts treatment outcomes in complicated UTI and pneumonia 2, 6

Drug Interactions

• Can interfere with serum methotrexate assays using bacterial dihydrofolate reductase 1
• May overestimate creatinine by ~10% using Jaffé alkaline picrate reaction 1
• Increased digoxin levels possible, especially in elderly patients 1

Treatment Failure Assessment

Reassess at 48-72 hours if no clinical improvement 2

In HIV-endemic areas, reassess at 48 hours rather than 72 hours 2

Practical Administration

Compliance and Acceptability

Co-trimoxazole in prophylactic dosing has proven acceptable with good compliance and minimal adverse effects in long-term use 3

Age-based dosing regimens are justified and generate effective plasma concentrations in children aged 1-48 months 7