What is the recommended treatment for varicella?

Treatment of Varicella

For otherwise healthy children and adults with varicella, oral acyclovir (20 mg/kg four times daily for children, 800 mg five times daily for adults) should be initiated within 24 hours of rash onset to reduce disease severity and duration, though it is most beneficial for high-risk populations including adults, immunocompromised patients, and pregnant women with complications. 1, 2

Treatment Approach by Patient Population

Healthy Children (2-12 years)

• Oral acyclovir at 20 mg/kg (maximum 800 mg) four times daily for 5 days reduces the maximum number of lesions, shortens time to healing, and decreases fever duration when started within 24 hours of rash onset 2, 3
• Treatment shortened time to 50% healing and reduced median number of vesicles in clinical trials of 993 pediatric patients 2
• Important caveat: Acyclovir does not decrease transmission of varicella or reduce duration of school absence, so its routine use in healthy children remains optional 1
• Treatment must begin within the first 24 hours of rash to be effective; later initiation provides no benefit 1, 4

Healthy Adults (>12 years)

• Oral acyclovir 800 mg five times daily for 7 days is recommended, as adults are at higher risk for moderate to severe disease 5, 2
• Early treatment (within 24 hours) reduced total time to 100% crusting from 7.4 to 5.6 days and decreased maximum lesion count by 46% 4
• Treatment initiated 25-72 hours after rash onset showed no benefit in uncomplicated adult varicella 4

Immunocompromised Patients

• Intravenous acyclovir 500 mg/m² or 10 mg/kg every 8 hours for 7 days is the standard of care for immunocompromised patients with varicella 6, 7
• IV acyclovir decreases cutaneous and visceral dissemination, reduces complications, and promotes more rapid resolution 6, 7
• Oral acyclovir 800 mg five times daily for 7 days can be considered for carefully selected immunocompromised children under close physician observation, though IV remains preferred 8
• In one study of 25 immunocompromised children treated with oral acyclovir, only 2 required transfer to IV therapy compared to 12 of 25 historical placebo controls 8

Pregnant Women

• For pregnant women with serious varicella complications (e.g., pneumonia), intravenous acyclovir should be administered 5, 9
• Acyclovir is FDA Category B in pregnancy, with a registry of 596 first-trimester exposures showing no increased rate of birth defects compared to the general population 5, 9
• Routine oral acyclovir is not recommended for mild, uncomplicated varicella in pregnancy 9
• Pregnant women at increased risk for moderate to severe disease should be considered for acyclovir treatment 9

Neonates

• Neonates whose mothers developed varicella from 5 days before to 2 days after delivery require Varicella-Zoster Immune Globulin (VZIG) administration, as these infants are at highest risk for severe disease and mortality 1, 9
• Premature infants born at <28 weeks gestation or weighing <1,000g with postnatal exposure require VZIG regardless of maternal immunity 1
• Premature infants born at ≥28 weeks gestation with postnatal exposure whose mothers lack immunity also require VZIG 1

Post-Exposure Prophylaxis

High-Risk Populations

• VZIG is the first-line prophylaxis for immunocompromised patients, pregnant women, and neonates after varicella exposure 1, 10
• VZIG dosing: 125 units/10 kg body weight (maximum 625 units) administered intramuscularly within 96 hours of exposure 1, 10
• VZIG provides approximately 3 weeks of protection 10

When VZIG is Unavailable or Delayed

• Oral acyclovir 20 mg/kg (maximum 800 mg) four times daily for 5-7 days can be used as alternative prophylaxis, initiated 7-10 days after exposure 10
• For pregnant women when VZIG is unavailable, oral acyclovir 10 mg/kg four times daily for 7 days can be considered 10
• Critical limitation: Acyclovir prophylaxis only provides protection during the treatment period, unlike VZIG's 3-week coverage 10

Healthy Individuals Without Immunity

• Vaccination is the method of choice for post-exposure prophylaxis in otherwise healthy children, adolescents, and adults without evidence of immunity 5, 1
• Acyclovir is not indicated for prophylactic use in healthy individuals after varicella exposure 5

Important Clinical Considerations

Timing of Treatment

• Maximum effectiveness requires initiation within 24 hours of rash onset—this is the most critical factor determining treatment success 1, 4, 3
• Treatment started after 24 hours in healthy individuals provides minimal to no benefit 4

Dosing Adjustments

• Adequate hydration and urine flow must be maintained with high-dose acyclovir therapy 7
• Mental status monitoring is required, particularly with IV administration 7
• Renal function impairment requires downward dosage adjustment 7
• Coadministration with probenecid increases acyclovir half-life and reduces renal clearance 2, 6

Treatment Limitations

• Acyclovir does not affect varicella-zoster virus-specific immune responses at 1 month or 1 year following treatment 2
• Treatment does not prevent transmission or reduce contagious period 1
• The low frequency of serious complications (pneumonia, encephalitis) in healthy individuals makes it difficult to assess acyclovir's impact on these rare outcomes 4, 3