What is the recommended dosage of acyclovir for an 11.5kg pediatric patient requiring 20mg/kg?

Acyclovir Dosing for 11.5kg Pediatric Patient

For an 11.5kg child requiring 20mg/kg acyclovir, administer 230mg (approximately 9.2mL of the 400mg/5mL oral suspension) per dose. 1

Dose Calculation

• Target dose: 20mg/kg × 11.5kg = 230mg per dose 1
• Volume to administer: Using 400mg/5mL suspension (80mg/mL concentration):
  • 230mg ÷ 80mg/mL = 2.875mL
  • However, this appears to be an error in your preparation concentration

Critical Preparation Issue

The preparation you've described (400mg/5mL) is NOT a standard acyclovir oral suspension concentration. 2 The standard commercially available acyclovir oral suspension is typically 200mg/5mL (40mg/mL), not 400mg/5mL. 2

Correct Dosing Based on Standard Preparation

If using standard 200mg/5mL suspension:

• For 230mg dose: 5.75mL per dose 2

Dosing Frequency by Indication

For Neonatal HSV (CNS or Disseminated Disease):

• 20mg/kg IV every 8 hours (3 times daily) for 21 days 1
• Note: This is IV dosing, not oral 1

For Neonatal HSV (Skin, Eye, or Mouth Disease):

• 20mg/kg IV every 8 hours (3 times daily) for 14 days 1

For VZV Prophylaxis (Post-Exposure):

• 10mg/kg orally four times daily for 7 days 1
• For this 11.5kg child: 115mg (approximately 2.9mL of 200mg/5mL suspension) four times daily 1

For VZV Treatment (Chickenpox with Severe Immunosuppression):

• 10mg/kg IV three times daily for 7-10 days 1

Critical Safety Considerations

• Renal function monitoring is essential - acyclovir is primarily renally excreted via glomerular filtration and tubular secretion 2, 3, 4
• Adequate hydration must be maintained to prevent crystalluria and elevated serum creatinine, which are the most important adverse effects related to acyclovir administration 3, 5
• Dosage adjustment required if renal impairment present 2, 4
• Administer with or without food - food does not affect absorption 2

Administration Guidance

• Oral acyclovir may be administered without regard to meals, though administration with meals may improve gastrointestinal tolerability 2
• Ensure accurate measurement using an oral syringe for precise dosing 2

Common Pitfall to Avoid

Do not confuse oral dosing (typically 10-20mg/kg) with IV dosing schedules - the 20mg/kg dose you've specified is typically used for serious neonatal HSV infections requiring IV administration, not routine oral therapy 1