Can I split an acyclovir tablet for an 11‑year‑old child to achieve the appropriate weight‑based dose?

Can You Split Acyclovir Tablets for Pediatric Dosing?

You should use the commercially available acyclovir oral suspension (6 mg/mL) rather than splitting tablets to achieve accurate weight-based dosing in an 11-year-old child. 1

Why Oral Suspension is Preferred Over Tablet Splitting

• Acyclovir oral suspension provides precise weight-based dosing at 20 mg/kg per dose (maximum 400 mg/dose) three times daily, which is the CDC-recommended regimen for pediatric HSV infections 1, 2

• Tablet splitting introduces significant dosing errors in pediatric populations—research on antiepileptic drugs showed that 49% of split tablet parts exceeded acceptable weight deviation limits, and 41.5% fell outside acceptable drug content specifications 3

• The oral suspension is specifically designed for children and eliminates the risk of dose variability that occurs with manual tablet splitting 1

Practical Dosing Algorithm for an 11-Year-Old

Step 1: Calculate the dose

• Multiply the child's weight in kg by 20 mg/kg (maximum 400 mg per dose) 1, 2
• For example: A 30 kg child requires 600 mg per dose, but this is capped at 400 mg 1

Step 2: Convert to suspension volume

• The suspension concentration is 6 mg/mL 4
• Volume (mL) = prescribed dose (mg) ÷ 6 mg/mL 4
• For a 400 mg dose: 400 ÷ 6 = 66.7 mL (approximately 67 mL) 4

Step 3: Administer three times daily

• Continue for 5-10 days until complete lesion healing 1, 2

When Tablets Might Be Considered

• For adolescents ≥45 kg who can swallow whole tablets, the CDC recommends acyclovir 400 mg tablets twice daily (not split) for genital herpes 2

• If suspension is unavailable, pharmacies can compound a 6 mg/mL suspension from tablets following package label instructions 4

Critical Safety Considerations

• Ensure adequate hydration throughout treatment to prevent acyclovir crystalluria 1, 5

• Monitor for clinical improvement within 48-72 hours of starting therapy 1, 5

• Watch for neutropenia with prolonged courses (occurs in 21-46% of infants on extended therapy, though typically self-limited) 1

• Adjust dose if renal insufficiency develops, as acyclovir is primarily eliminated by the kidneys 5

Common Pitfalls to Avoid

• Do not stop treatment when symptoms improve—continue until complete healing occurs 1, 2

• Do not use topical acyclovir alone, as it cannot reach the site of viral reactivation or impact host immune response 1

• Do not delay treatment—initiate within the first 3 days of symptom onset for maximum efficacy 1, 2

If Treatment Fails

• Consider acyclovir-resistant HSV if no clinical response occurs after 5-7 days of appropriate therapy 1, 5

• Switch to intravenous foscarnet 40 mg/kg per dose three times daily for documented resistance 1, 5, 2