Varicella Drug Summary

Last updated: 15 December 2025
Reviewed by

Content on this page:

Antivirals

Content on this page:

Antivirals

Antivirals

Drug Dosage Remarks
Aciclovir (Acyclovir) Varicella
Immunocompetent:
800 mg PO 4 hourly (omit night-time dose) x 5-7 days
Immunocompromised: 10 mg/kg IV 8 hourly x 7-10 days
Herpes Zoster
Immunocompetent: 800 mg PO 4 hourly x 5-7 days (omit night-time dose) or 5 mg/kg IV 8 hourly
Immunocompromised: 10 mg/kg IV 8 hourly x 7-10 days
 Adverse Reactions
  • GI effects  (nausea/vomiting, diarrhea, occasionally increased serum bilirubin, liver enzymes); CNS effects (headache, dizziness); Other effects (hematologic changes, skin rashes, fever, transient increase in BUN and creatinine)
  • IV: Inflammation, injection site phlebitis, renal impairment (reversible with hydration, dosage reduction/withdrawal)
Special Instructions
  • Parenteral administration by slow IV over 1 hour to avoid precipitation in kidney; avoid rapid bolus injection
  • Use with caution in patients with renal impairment (adjust dose according to creatinine clearance), neurologic abnormalities, significant hypoxia, serious hepatic or electrolyte abnormalities
  • Maintain adequate hydration
Famciclovir  Varicella
Immunocompetent: 
500 mg PO 8 hourly x 5-7 days
Immunocompromised: 
Step-down from IV Aciclovir for a total of 7-10 treatment days
500 mg PO 8 hourly
Herpes Zoster
Immunocompetent: 250-500 mg PO 8 hourly x 7 days
Immunocompromised: 500 mg PO 8 hourly x 7-10 days 

Adverse Reactions

  • CNS effects (headache, dizziness, confusion, hallucinations); GI effects (nausea/vomiting, abdominal pain); Hematologic effects (granulocytopenia, thrombocytopenia); Other effects (fever, skin rash)

Special Instructions

  • Reduce dose in patients with renal impairment
Valaciclovir  Varicella
Immunocompetent: 1,000 mg PO 8 hourly x 5 days
Immunocompromised: 1,000 mg PO 8 hourly x 5-7 days
Herpes Zoster
Immunocompetent: 1,000 mg PO x 7 days
Immunocompromised: 1,000 mg PO 8 hourly x 7 days and for 2 more days following crusting of lesions 

Adverse Reactions

  • GI effects  (nausea/vomiting, diarrhea, occasionally increased serum bilirubin, liver enzymes); CNS effects (headache, dizziness); Other effects (hematologic changes, skin rashes, fever, transient increase in BUN and creatinine)
  • IV: Inflammation, injection site phlebitis, renal impairment (reversible with hydration, dosage reduction/withdrawal)

Special Instructions

  • Parenteral administration by slow IV over 1 hour to avoid precipitation in kidney; avoid rapid bolus injection
  • Use with caution in patients with renal impairment (adjust dose according to creatinine clearance), neurologic abnormalities, significant hypoxia, serious hepatic or electrolyte abnormalities
  • Maintain adequate hydration

Vaccines, Antisera & Immunologicals

Drug Dosage Remarks
Herpes zoster vaccine 
(Recombinant)
(Herpes zoster virus vaccine)		 ≥50 and ≥18 years old (at increased risk for herpes zoster): 0.5 mL IM followed by second dose after 2-6 months
 Adverse Reactions
  • Musculoskeletal effect (myalgia); Local effects (injection site reactions: Pain, redness, swelling): Other effects (fever, fatigue, shivering, GI symptoms)
Special Instructions
  • Contraindicated in patients with previous anaphylactic reaction to any component of the vaccine
Varicella-zoster vaccine 
(Live, attenuated)1
(Varicella-zoster virus vaccine) 		 0.5 mL SC followed by second dose after 4-8 weeks
≥50 years old: 0.65 mL SC as single dose 

Adverse Reactions

  • Local effects (injection site reactions [inflammation, soreness, rash, erythema, induration], generalized varicella-like rashes); Other effect (anaphylaxis)
  • May be followed by fever, headache and malaise starting a few hours after injection and lasting for 1-2 days
  • Virus may become latent and result in late development of zoster infection

Special Instructions

  • Contraindicated in pregnancy, immunodeficiency, clinical AIDS, active and untreated tuberculosis, prior use of high-dose corticosteroids, previous anaphylactic reaction to any component of the vaccine, recent (within the past 3 months) treatment with IgG by IM or recent (within 9 months) treatment with IgG
Varicella-zoster immunoglobulin 
(Varicella-zoster virus IgG) 		 Adult >40 kg: 625 units as single deep IM injection
Divide dose and administer at different sites if >5 mL
May repeat dose at 3-week intervals if patients is re-exposed or continuously exposed to varicella until the risk of exposure is no longer present

Adverse Reactions

  • Local effects (injection site reactions [erythema, rash, pain, tenderness]); Other effects (fever, chills, facial flushing, headache, arthralgia, nausea)

Special Instructions

  • IgG may interfere with the ability of live vaccines to induce an immune response
    • Separate administration of the two products by a suitable interval
  • Dose should preferably be given within 48 hours after exposure but no later than 96 hours after exposure
1Combination with measles, mumps and rubella (MMR) vaccine is available. Please see the latest MIMS for specific formulations and prescribing informaiton.

Disclaimer

All dosage recommendations are for non-pregnant and non-breastfeeding women, and non-elderly adults with normal renal and hepatic function unless otherwise stated.  
Not all products are available or approved for above use in all countries.  
Products listed in the Drug Summary are based on indications stated in the locally approved product monographs.   
Please refer to local product monographs in Related MIMS Drugs for country-specific prescribing information.  

Related MIMS Drugs