What is the recommended treatment approach for a patient with chickenpox, especially for those with weakened immune systems or other high-risk factors?

Treatment of Chickenpox

For immunocompetent adolescents ≥12 years and adults, initiate oral acyclovir 800 mg five times daily for 5-7 days within 24 hours of rash onset; for immunocompromised patients, administer intravenous acyclovir 10 mg/kg every 8 hours for 7-10 days immediately upon diagnosis. 1, 2

Treatment Algorithm by Patient Population

Immunocompetent Children and Adolescents

• Children <40-45 kg: Administer oral acyclovir 20 mg/kg per dose (maximum 800 mg) four times daily for 5 days 1, 2
• Adolescents ≥12 years and children >40 kg: Administer oral acyclovir 800 mg orally four times daily for 5 days 1, 2
• Treatment must begin within 24 hours of rash onset for maximum clinical benefit, as delayed initiation significantly reduces efficacy 1, 2
• Five days of therapy is sufficient for immunocompetent patients, as extending to 7 days provides no additional benefit 1

Immunocompetent Adults

• Standard dosing: Oral acyclovir 800 mg five times daily (every 4 hours while awake) for 7-10 days 1, 2
• Adults are at substantially higher risk for complications including pneumonitis, visceral dissemination, and hemorrhagic manifestations compared to children 3, 4
• Critical timing: Initiate therapy within 24 hours of rash onset; efficacy when started >24 hours after onset has not been established 2, 5

Immunocompromised Patients (High-Priority Population)

• Mandatory intravenous therapy: Acyclovir 10 mg/kg IV every 8 hours for 7-10 days or until no new lesions appear for 48 hours 1, 6, 2
• Alternative dosing in children >1 year: 500 mg/m² IV every 8 hours 1
• Discontinue immunomodulator therapy immediately in severe cases if clinically feasible 1, 7
• Do not commence or continue immunosuppressive therapy during active infection—this substantially increases mortality risk 7
• Intravenous acyclovir prevents visceral dissemination, halts progression, and reduces complications 3, 4

High-Risk Groups Requiring Antiviral Treatment

The following populations should receive acyclovir therapy regardless of disease severity 1, 6:

• Patients with chronic cutaneous or pulmonary disorders 1, 6
• Patients receiving long-term salicylate therapy 1, 6
• Patients on short, intermittent, or aerosolized corticosteroid therapy 1, 6
• Secondary household contacts of infected children 1
• Pregnant women (though routine use is not generally recommended; acyclovir is Pregnancy Category B) 1

Post-Exposure Prophylaxis Strategy

For Immunocompromised Patients and High-Risk Individuals

• First-line: Administer Varicella-Zoster Immune Globulin (VZIG) as soon as possible, ideally within 96 hours of exposure (some sources extend to 10 days) 8, 1, 6
• If VZIG unavailable: Administer oral acyclovir 10 mg/kg four times daily for 7 days, starting 7-10 days after exposure 1, 6
• VZIG may prolong the incubation period from 21 to 28 days, requiring extended monitoring 8, 7

Specific High-Risk Populations Requiring VZIG

• Pregnant women without evidence of immunity 1, 6
• Neonates born to mothers with varicella 5 days before to 2 days after delivery 1, 6
• Premature infants <28 weeks gestation or <1,000 g regardless of maternal immunity 1, 6
• Immunocompromised patients of all ages 8

Post-Exposure Vaccination

• For susceptible individuals with no contraindications: Administer varicella vaccine within 3-5 days of exposure, which may modify disease if infection has not yet occurred 8, 7
• Vaccination >5 days post-exposure still provides protection against subsequent exposures 8
• Delay varicella vaccination 5 months after VZIG administration 1, 6

Infection Control Measures

• Isolate patients until all lesions have crusted over—this is when infectivity ceases 8, 1
• Implement airborne precautions (negative air-flow rooms) and contact precautions for all hospitalized patients with varicella 8
• Healthcare workers without immunity exposed to VZV should be furloughed from days 10-21 after exposure (extended to days 8-28 if VZIG administered) 8, 7
• Only healthcare personnel with evidence of immunity should care for patients with confirmed or suspected varicella 8

Vaccination Considerations in Treatment Context

• Live varicella vaccination is absolutely contraindicated in immunocompromised patients due to risk of disseminated viral infection 1, 7, 6
• Susceptible household contacts of immunocompromised patients should be vaccinated to prevent transmission 1, 6
• For patients on immunomodulators: Complete the two-dose varicella vaccine series at least 3 weeks prior to starting immunosuppressive therapy 7
• If already on immunosuppression, vaccination requires 3-6 months cessation of all immunosuppressive therapy before and after administration 7

Dosage Adjustments for Renal Impairment

• Creatinine clearance 10-25 mL/min: Reduce 800 mg dose to every 8 hours 2
• Creatinine clearance 0-10 mL/min: Reduce 800 mg dose to every 12 hours 2
• Hemodialysis patients: Administer additional dose after each dialysis session due to 60% decrease in plasma concentrations during 6-hour dialysis 2
• Maintain adequate hydration and urine flow, especially at higher doses 4

Critical Clinical Caveats

• Timing is everything: The evidence demonstrates a clear gradient in treatment efficacy, with maximum benefit within 24 hours of rash onset 1, 2
• Acyclovir does not eradicate latent virus or affect subsequent risk, frequency, or severity of herpes zoster 1
• Antibody titers after infection in children receiving acyclovir do not differ substantially from untreated patients 1
• Monitor mental status in patients receiving high-dose therapy, as neurological side effects can occur 4
• Never rely on antibody titers in patients with nephrotic-range proteinuria or receiving IVIG, as results are unreliable 6
• Between 30-35% of adults remain susceptible to VZV—never assume immunity based on age alone; always verify history or serology 7

Common Pitfalls to Avoid

• Do not delay treatment waiting for laboratory confirmation—initiate therapy based on clinical diagnosis within 24 hours 1, 2
• Do not continue immunosuppressive therapy during active varicella infection in severe cases, as this substantially increases mortality risk (5 of 20 IBD patients with varicella died in one review) 7
• Do not use latex agglutination tests alone for screening healthcare personnel, as false-positive results can lead to unvaccinated susceptible workers subsequently contracting varicella 8
• Do not administer acyclovir prophylactically to healthy individuals after exposure—reserve for high-risk populations 1