Trimethoprim-Sulfamethoxazole (Bactrim) Prescription for Impetigo in a 19-Month-Old
For a 19-month-old infant weighing 12.9 kg with impetigo, the appropriate Bactrim dosage is 8-12 mg/kg/day (based on trimethoprim component) divided into two doses for 7 days. 1
Prescription Details
- Medication: Trimethoprim-Sulfamethoxazole (Bactrim) suspension (40 mg TMP/200 mg SMX per 5 mL)
- Dosage: 2.5 mL twice daily for 7 days 1
- Total daily dose: 5 mL (40 mg TMP/200 mg SMX per day)
- Route: Oral
- Instructions: Give 2.5 mL by mouth twice daily for 7 days
- Quantity: 35 mL (sufficient for 7-day course)
Rationale for Treatment
- Trimethoprim-sulfamethoxazole is effective against both Staphylococcus aureus and Streptococcus pyogenes, the primary causative organisms of impetigo 2
- The calculated dose of 8-12 mg/kg/day (based on trimethoprim component) provides appropriate coverage for skin and soft tissue infections 1
- For this 12.9 kg child, the daily dose of trimethoprim component is approximately 10 mg/kg/day, which falls within the recommended range 1
Clinical Considerations
- Bactrim is particularly useful when there is concern for methicillin-resistant Staphylococcus aureus (MRSA), as it provides good coverage 2
- While topical antibiotics are often first-line for limited impetigo, oral antibiotics may be preferred when lesions are more extensive or in areas difficult to treat topically 2, 3
- A 7-day course is appropriate for uncomplicated skin infections 1
- Monitor for potential side effects, including gastrointestinal symptoms and rare but serious skin reactions 1
Important Precautions
- Parents should be advised to complete the full 7-day course even if symptoms improve earlier 1
- If no improvement is seen within 48-72 hours, reevaluation is recommended 2
- Bactrim should be used with caution in infants under 2 months due to risk of kernicterus, but is safe for a 19-month-old 1
- Ensure adequate hydration during treatment to prevent crystalluria 1
Alternative Options
- If the patient has a sulfa allergy or treatment failure occurs, alternative options include:
The dosage provided is based on pediatric guidelines and takes into account the child's weight to ensure optimal efficacy while minimizing potential adverse effects 1.