Aciclovir Intravenous Infusion for Adults

Who can administer

May be administered by registered competent doctor or nurse/midwife

Important information

  • Must ensure adequate hydration and give over recommended time (to avoid potential renal tubular damage)
  • See under 'Dose' for adjustments required in renal impairment
  • See under 'Dose' for considerations in obesity

Available preparations

Aciclovir 250mg per 10ml vial

Zovirax 250mg vial



Already in solution

Dilute further prior to administration

Zovirax brand

Water for injection or Sodium chloride 0.9%

10ml per 250mg vial

Dilute further prior to administration

Infusion fluids

Sodium Chloride 0.9%

Glucose 5% (unlicensed) (ref 1)

Methods of intravenous administration

Intermittent intravenous infusion (administer using an electronically controlled infusion device)

Dilute with infusion fluid to a concentration not greater than 5mg/ml (0.5%w/v)
Doses of 250 to 500mg 100ml infusion fluid

Administer required dose over 60 minutes

Sixty minute infusion time reduces the risk of renal tubular damage

Doses between 501mg and 1000mg 250ml infusion fluid
Fluid restricted patient (central line) (ref 3) May be infused at a concentration of 25mg/ml - ie 250mg per 10ml

Dose in adults

Herpes simplex infections (other than encephalitis) (treatment)

  • Give 5mg per kg every eight hours
  • Higher dose may be required in severe infection/immunocompromised. Discuss with Microbiology or Infectious Diseases (ref 2)

Herpes simplex encephalitis

  • Give 10mg per kg every eight hours (for 14 to 21 days)

Herpes simplex infections (prophylaxis in immunocompromised) (ref 3)

  • Give 5mg per kg every eight hours

    Varicella zoster (chickenpox)or Herpes zoster(shingles)infections

    • NOT immunocompromised: give 5mg per kg every eight hours
    • Immunocompromised, or severe /complicated infections: give 10mg per kg every eight hours


    • Limited data available on aciclovir intravenous dosing in obesity (BMI greater than or equal to 30 kg/m2 )
    • Ideal Body Weight (IBW) has been used, as dosing based on Total Body Weight can result in overdosing and subsequent toxicity
    • However, use of IBW in morbidly obese patients (BMI greater than or equal to 40 kg/m2 ) can result in underdosing. Use of Adjusted body weight (Adj BW) in these patients may be considered - see calculations below(ref 4)
    • Take type and severity of infection and patients renal function into account when choosing dose in obese patients
    • Monitor patient for nephrotoxicity or neurotoxicity when using large doses
    • Contact Microbiology or antimicrobial pharmacist for advice if necessary
    • The GAPP gentamicin calculator can be used to calculate ideal and adjusted body weight (=Dosing weight) for your patient. Alternatively, the calculations may be done manually using the following formulas
      • Ideal body weight (IBW) calculations (ref 2)
      • Male 50kg + (2.3 x inches over 5 feet) or 50kg + (0.9 x cm over 152 cm)
      • Female 45.5kg + (2.3 x inches over 5 feet) or 45.5kg + (0.9 x cm over 152 cm)
      • Adjusted body weight (Adj BW) = (IBW + 0.4 x [TBW-IBW])
      • (where TBW = total body weight or actual weight)
    Renal impairment
    eGFR Dose
    25 to 50ml/minute/1.73m2 give recommended dose every 12 hours
    10 to 25ml/minute/1.73m2 give recommended dose once every 24 hours
    less than 10ml/minute/1.73m2 give 50% of recommended dose every 24 hours
    Dialysis consult specialist literature or pharmacy


    • Monitor renal function regularly
    • Ensure adequate hydration
    • Monitor for neurological side-effects


    • Store below 250C
    • Do not refrigerate as precipitation may occur


    Zovirax SPC Sept 2021

    1. Injectable medicines administration guide accessed online via Medusa 14/03/2022

    2: Gapp app

    3. BNF accessed online via Medicinescomplete 24/03/2022

    4. Sanford Guide to antimicrobial therapy accessed online 24/03/2022

    Therapeutic classification

    Antiviral agent