Purpose of Bactrim in Babies Exposed to HIV
Bactrim (trimethoprim-sulfamethoxazole) is primarily used in HIV-exposed infants to prevent Pneumocystis jiroveci pneumonia (PCP), a potentially fatal opportunistic infection that occurs with high frequency in HIV-infected infants, particularly during their first year of life. 1, 2
Primary Indication: PCP Prophylaxis
- Bactrim is FDA-approved for prophylaxis against Pneumocystis jiroveci pneumonia in immunosuppressed individuals considered at increased risk of developing PCP 1, 2
- All HIV-exposed infants should start PCP prophylaxis with Bactrim at 4-6 weeks of age, even when HIV infection status has not yet been definitively established 3
- Bactrim has been shown to substantially reduce the risk of PCP among HIV-infected children 3
Timing and Dosage
- Prophylaxis should begin at 4-6 weeks of age for all HIV-exposed infants 3
- The recommended dosage is TMP-SMX 150/750 mg/m² body surface area per day divided into 2 doses and administered 3 times weekly on consecutive days 3
- Alternative acceptable dosing schedules include:
- Single dose orally 3 times weekly on consecutive days
- Two divided doses orally daily
- Two divided doses orally 3 times weekly on alternate days 3
Duration of Prophylaxis
- For HIV-infected infants aged 1-12 months: continue prophylaxis regardless of CD4 count 3
- For HIV-infected children aged 1-5 years: continue prophylaxis if CD4 count is <500 cells/mm³ or CD4 percentage is <15% 3
- For HIV-infected children aged 6-12 years: continue prophylaxis if CD4 count is <200 cells/mm³ or CD4 percentage is <15% 3
- For HIV-exposed but uninfected infants: prophylaxis can be discontinued once HIV infection has been reasonably excluded 3
Rationale for PCP Prophylaxis in HIV-Exposed Infants
- Young HIV-infected infants have a relatively high risk for PCP 3
- PCP in infants has a frequently sudden onset and high mortality rate 3
- Studies show PCP is a common cause of hypoxic pneumonia and mortality in HIV-infected South African infants 4
- Without prophylaxis, PCP can occur in HIV-infected infants even with relatively high CD4 counts compared to adults 3
- In one study, 90% of HIV-infected infants who developed PCP had CD4 counts less than 1,500/mm³ 3
Effectiveness and Safety
- Bactrim has been shown to substantially reduce the risk for PCP among HIV-infected children 3
- A Cochrane review found an 85% reduction in PCP occurrence in immunocompromised patients receiving trimethoprim/sulfamethoxazole prophylaxis 5
- The same review found PCP-related mortality was significantly reduced with prophylaxis (RR 0.17,95% CI 0.03 to 0.94) 5
- Adverse reactions can occur in approximately 40% of HIV-infected children, with erythema multiforme (70%) and neutropenia (20%) being most common 6
- Thrice-weekly dosing may be better tolerated than daily dosing 7
Important Considerations
- Despite prophylaxis, some children may still develop PCP 3
- Underuse of prevention programs and failure to institute trimethoprim-sulfamethoxazole prophylaxis are important obstacles to reducing PCP incidence 4
- Adherence to the prophylaxis regimen is critical and requires caregiver education about:
- The high risk of PCP in young infants
- The importance of starting prophylaxis at 4-6 weeks of age
- The potentially fatal nature of PCP in infants 3
- Contrary to some concerns, evidence suggests that TMP-SMX prophylaxis may actually protect against bacterial resistance to other antibiotics rather than promote it 8