Therapeutic Classification: antivirals
Pharmacologic Classification: purine analogues
Absorption: Despite poor absorption (15–30%), therapeutic plasma concentrations are achieved.
Distribution: Widely distributed. CSF concentrations are 50% of plasma.
Metabolism/Excretion: >90% eliminated unchanged by kidneys; remainder metabolized by liver.
Half-Life: Neonates: 4 hr; Children (1–12 yr): 2–3 hr; Adults: 2–3.5 hr (↑ in renal failure).
Initial Genital Herpes
- PO (Adults and Children ): 200 mg every 4 hr while awake (5 times/day) for 7–10 days or 400 mg every 8 hr for 7–10 days; maximum dose in children: 80 mg/kg/day in 3–5 divided doses.
- IV (Adults and Children ≥12 yr): 5 mg/kg every 8 hr for 5 days.
Chronic Suppressive Therapy for Recurrent Genital Herpes
- PO (Adults and Children ): 400 mg twice daily or 200 mg 3–5 times/day for up to 12 mo. Maximum dose in children: 80 mg/kg/day in 2–5 divided doses.
Intermittent Therapy for Recurrent Genital Herpes
- PO (Adults and Children ): 200 mg every 4 hr while awake (5 times/day) or 400 mg every 8 hr or 800 mg every 12 hr for 5 days, start at first sign of symptoms. Maximum dose in children: 80 mg/kg/day in 2–5 divided doses.
Acute Treatment of Herpes Zoster in Immunosuppressed Patients
- PO (Adults ): 800 mg every 4 hr while awake (5 times/day) for 7–10 days. Prophylaxis: 400 mg 5 times/day.
- PO (Children ): 250–600 mg/m2/dose 4–5 times/day.
Herpes Zoster in Immunocompetent Patients
- PO (Adults and Children ): 4000 mg/day in 5 divided doses for 5–7 days, maximum dose in children: 80 mg/kg/day in 5 divided doses.
Chickenpox
- PO (Adults and Children ): 20 mg/kg (not to exceed 800 mg/dose) 4 times daily for 5 days. Start within 24 hr of rash onset.
Mucosal and Cutaneous Herpes Simplex Infections in Immunosuppressed Patients
- IV (Adults and Children >12 yr): 5 mg/kg every 8 hr for 7 days.
- IV (Children 3 mo–12 yr): 10 mg/kg every 8 hr for 7 days.
- (Adults ): 0.5 in. ribbon of 5% ointment for every 4-square-in. area every 3 hr (6 times/day) for 7 days.
Herpes Simplex Encephalitis
- IV (Adults and Children ≥12 yr): 10 mg/kg every 8 hr for 10 days.
- IV (Children 3 mo–12 yr): 20 mg/kg every 8 hr for 10 days.
- IV (Children birth–3 mo): 20 mg/kg every 8 hr for 14–21 days.
- IV (Neonates , premature): 10 mg/kg every 12 hr for 14–21 days.
Neonatal Herpes Simplex Infections
- IV (Children post-menstrual age of ≥34 wk): 20 mg/kg every 8 hr for 21 days.
- IV (Children post-menstrual age of <34 wk): 20 mg/kg every 12 hr for 21 days.
Varicella Zoster Infections in Immunosuppressed Patients
- IV (Adults and Children ≥12 yr): 10 mg/kg every 8 hr for 7 days.
- IV (Children <12 yr): 20 mg/kg every 8 hr for 7 days.
Renal Impairment
- PO IV (Adults and Children >3 mo): CCr 25.1–50 mL/min/1.73 m2: Normal dose every 12 hr; CCr 10.1–25 mL/min/1.73 m2: Normal dose every 24 hr; CCr ≤10 mL/min/1.73 m2: 50% of dose every 24 hr.
Herpes Labialis
- (Adults and Children >12 yr): Apply 5 times/day for 4 days; start at first symptoms.
(Adults ): Apply one 50–mg buccal tablet to the upper gum region within 1 hr of onset of prodromal symptoms (but before appearance of any lesions).
