What is the recommended treatment for a patient with chicken pox, particularly for those with underlying health conditions or at high risk of complications?

Treatment of Chickenpox

For immunocompromised patients, initiate intravenous acyclovir 10 mg/kg every 8 hours immediately upon diagnosis, regardless of timing; for otherwise healthy adults and adolescents ≥13 years, start oral acyclovir 800 mg four times daily for 5 days only if within 24 hours of rash onset. 1, 2, 3

Risk Stratification and Treatment Algorithm

Immunocompromised Patients (Highest Priority)

• Immediate IV acyclovir is mandatory for all immunocompromised patients including HIV-infected individuals, transplant recipients, cancer patients on chemotherapy, and those receiving high-dose corticosteroids 1, 2
• Dosing: 10 mg/kg IV every 8 hours for 7-10 days 1, 3
• Critical action: Discontinue immunomodulator therapy immediately during active infection in severe cases, as mortality risk is substantially increased if immunosuppression continues 1
• Therapy can only be reintroduced after all vesicles have crusted over and fever has resolved 1

Adults and Adolescents ≥13 Years (Otherwise Healthy)

• Oral acyclovir 800 mg four times daily for 5 days if started within 24 hours of rash onset 1, 2, 3
• After 24 hours, acyclovir loses efficacy and is not recommended 2
• Adults face significantly higher complication rates than children, with case-fatality rates 21.3 per 100,000 versus 0.8 per 100,000 in children aged 1-4 years 2

Children <13 Years

• Supportive care only for otherwise healthy children 2
• Oral acyclovir 20 mg/kg (maximum 400 mg) four times daily for 5 days only if within 24 hours of rash onset AND one of the following: 1, 3
  • Chronic cutaneous disorders (e.g., eczema) 1, 2
  • Chronic pulmonary disorders 1
  • Long-term salicylate therapy 1
  • Weight >40 kg: use adult dose of 800 mg four times daily 3

Pregnant Women

• Oral acyclovir for uncomplicated disease if within 24 hours of rash onset 2
• IV acyclovir for serious complications such as pneumonia 2
• Acyclovir is FDA Pregnancy Category B with reassuring safety data from 596 first-trimester exposures showing no increased birth defects 4, 2

Post-Exposure Prophylaxis

High-Risk Individuals

• Varicella-Zoster Immune Globulin (VZIG) within 96 hours of exposure is first-line for: 1, 4, 2
  • Immunocompromised patients 1, 4
  • Pregnant women without immunity 4, 2
  • Neonates born to mothers with varicella from 5 days before to 2 days after delivery (regardless of whether mother received VZIG) 4, 2
  • Premature infants <28 weeks gestation or <1,000 g regardless of maternal immunity 4
• VZIG prolongs incubation period to 28 days, requiring extended monitoring 5, 4
• Dosing: 125 IU/10 kg IM, maximum 625 IU; minimum 62.5 IU for infants ≤2.0 kg 2

Susceptible Immunocompetent Individuals

• Varicella vaccine within 3-5 days of exposure is >90% effective at preventing disease 2
• If vaccine contraindicated or unavailable, acyclovir 20 mg/kg (maximum 800 mg) four times daily for 5-7 days starting 7-10 days after exposure 1, 4

Healthcare Personnel Management

• Unvaccinated HCP without immunity: furlough days 10-21 after exposure 5, 1
• HCP with 1 dose of vaccine: give second dose within 3-5 days of exposure (if ≥4 weeks since first dose), then monitor days 8-21 5, 1
• HCP with 2 doses: monitor daily for fever and rash days 8-21 post-exposure 5, 1

Infection Control Measures

• Airborne and contact precautions for all hospitalized patients 4
• Patients are infectious from 2 days before rash onset until all lesions are crusted (typically 5-7 days after rash onset) 4, 2
• Isolate until all lesions have crusted over 1, 4

Renal Dosing Adjustments

For patients with renal impairment receiving oral acyclovir 800 mg regimen: 3

• CrCl >25 mL/min: 800 mg every 4 hours, 5 times daily
• CrCl 10-25 mL/min: 800 mg every 8 hours
• CrCl 0-10 mL/min: 800 mg every 12 hours
• Hemodialysis: administer additional dose after each dialysis session 3

Critical Pitfalls to Avoid

• Never assume immunity based on age alone—always verify history or serology, especially in healthcare workers where birth before 1980 is not considered evidence of immunity 5, 1
• Never continue immunosuppressive therapy during active varicella in severe cases—this substantially increases mortality risk (5 of 20 IBD patients with varicella died in one review) 1
• Do not start acyclovir >24 hours after rash onset in immunocompetent patients—it is ineffective 2
• Avoid aspirin in children due to Reye's syndrome risk 4
• Do not confuse with herpes zoster treatment, which has a 72-hour window rather than 24-hour window 4
• Acyclovir is not indicated for prophylaxis in otherwise healthy individuals after exposure—vaccination is the method of choice 2