Acyclovir Use in a 1-Month-Old Baby
Acyclovir can be safely administered to a 1-month-old baby for treatment of herpes simplex virus (HSV) infections, with appropriate dosing and monitoring. 1
Indications for Acyclovir in Infants
- Acyclovir is the drug of choice for treatment of HSV infections in infants and children, regardless of HIV-infection status 1
- For neonatal HSV disease (CNS and disseminated disease), high-dose intravenous acyclovir (20 mg/kg body weight/dose three times daily) is recommended for 21 days 1
- For skin, eye, and mouth HSV disease in neonates, intravenous acyclovir should be administered for 14 days 1
- For symptomatic HSV gingivostomatitis in infants, either intravenous acyclovir (5-10 mg/kg/dose three times daily) or oral acyclovir (20 mg/kg/dose three times daily) for 7-14 days is recommended 1
Dosing Considerations for 1-Month-Old Infants
- Intravenous acyclovir is preferred over oral administration for infants younger than 2 years of age, especially for severe infections 2
- The elimination half-life of acyclovir decreases sharply during the first month after birth, from 10-15 hours to approximately 2.5 hours 3
- Acyclovir clearance is related to glomerular filtration rate, body surface area, and serum creatinine level, requiring careful dosing in young infants 3
Safety Profile and Monitoring
- The most common adverse events in infants receiving high-dose acyclovir include 4:
- Thrombocytopenia (25% of infants)
- Hypotension (9% of infants)
- Seizures (9% of infants)
- Renal toxicity is a concern but occurs infrequently, with elevated creatinine observed in only 2% of infants receiving high-dose acyclovir 4
- The risk of acute kidney injury (AKI) during acyclovir treatment in infants is relatively low (5.6%), but increases with 5:
- Confirmed HSV disease
- Receipt of ≥2 concomitant nephrotoxic medications
- Receipt of mechanical ventilation
- Admission to intensive care unit
Important Clinical Considerations
- Acyclovir therapy should not be discontinued in neonates with CNS disease unless a repeat CSF HSV DNA PCR assay is negative at day 19-21 of treatment 1
- Acyclovir is primarily excreted by the kidney; dose adjustment based on creatinine clearance is needed in patients with renal insufficiency 1
- Monitoring for neutropenia is recommended, as it was observed in 46% of infants receiving long-term oral acyclovir therapy, though it was generally self-limited 1
When to Consider Alternative Treatments
- For acyclovir-resistant HSV infections, intravenous foscarnet (120 mg/kg/day in 2-3 divided doses) is recommended until the infection resolves 1
- Foscarnet should be administered slowly over 2 hours (or no faster than 1 mg/kg/minute) with saline fluid loading to minimize renal toxicity 1