What is the recommended syrup aciclovir dosage for a pediatric patient with a viral infection?

Acyclovir Syrup Dosing for Pediatric Patients

For pediatric patients with viral infections requiring oral acyclovir suspension, the recommended dose is 20 mg/kg body weight per dose (maximum 400 mg/dose) administered 3-4 times daily, with specific frequency and duration determined by the type and severity of infection. 1

Dosing by Indication

Herpes Simplex Virus (HSV) Infections

Mild Symptomatic Gingivostomatitis or Mucocutaneous HSV:

• 20 mg/kg body weight per dose (maximum 400 mg/dose) orally 3 times daily for 5-10 days 1
• For children <45 kg with genital herpes: same dosing regimen for 5-14 days 1

Moderate to Severe Disease:

• Initial IV acyclovir 5-10 mg/kg per dose 3 times daily, then transition to oral acyclovir at 20 mg/kg per dose after lesions begin to regress 1
• Continue therapy until lesions completely heal 1, 2

Varicella Zoster Virus (VZV) Infections

Chickenpox in Immunocompromised Children:

• 20 mg/kg body weight orally per dose (maximum 800 mg/dose) 4 times daily for 7-10 days or until no new lesions for 48 hours 1
• This dosing applies to children with no or moderate immune suppression 1

Age-Specific Considerations

Neonates and Young Infants (<1 month):

• Higher doses are typically required: 20 mg/kg IV every 8 hours for serious HSV infections 1, 2
• For oral suspension in neonates: 24 mg/kg three times daily 3
• Elimination half-life is significantly prolonged in neonates (10-15 hours) compared to older infants (2.5 hours) 3

Infants 1-3 months:

• 24 mg/kg four times daily for oral suspension 3
• Bioavailability is approximately 12% in this age group 3

Children >3 months:

• Standard dosing of 20 mg/kg per dose applies 1
• For VZV infections, some evidence suggests a twofold dose increase may be necessary for adequate therapeutic levels 3

Critical Dosing Adjustments

Renal Function:

• Acyclovir clearance is directly related to estimated glomerular filtration rate (eGFR) 3, 4
• Dose reduction required in patients with impaired renal function 1
• For children with augmented renal clearance (eGFR >250 ml/min/1.73 m²), higher or more frequent dosing may be needed 4

Body Weight Considerations:

• Always calculate dose based on actual body weight 3, 4
• Maximum single dose caps at 400 mg for HSV and 800 mg for VZV regardless of weight 1

Administration and Monitoring

Key Clinical Points:

• Ensure adequate hydration throughout treatment to prevent crystalluria 5, 2
• Monitor for clinical improvement within 48-72 hours of initiating therapy 5, 2
• Watch for neutropenia with prolonged use, though uncommon with standard 5-10 day courses 5
• Monitor renal function, especially in neonates and patients receiving IV therapy 2, 6

Common Adverse Events:

• Thrombocytopenia occurs in approximately 25% of treated infants 6
• Elevated creatinine is rare (2% of infants), and renal failure requiring dialysis is extremely uncommon 6
• Most adverse events are mild and may be related to underlying infection rather than drug toxicity 6

Important Caveats

Treatment Timing:

• Treatment is most effective when started early in the disease course 5
• For chickenpox, initiate within 24 hours of rash onset for maximum benefit 5

Limitations:

• Acyclovir does not eradicate latent virus or affect risk of future recurrences 5
• For severe immune suppression (CDC category 3), IV therapy is preferred over oral 1

Alternative Formulations:

• Valacyclovir offers less frequent dosing but lacks pediatric-specific formulations and dosing data for young children 1
• Famciclovir similarly lacks pediatric preparations and dosing data 1