C difficile risk
Oral Bioavailability


Oral: 400 mg 3 times daily, beginning at 36 weeks' gestation and continued until delivery (If preterm delivery is predicted in a woman with recurrent genital herpes, then use of suppressive antivirals may be considered at an earlier gestational age)

Oral: 400 mg 3 times daily for 7 to 10 days; extend treatment duration if lesion has not healed completely after 10 days

IV (severe disease): 5 to 10 mg/kg intravenously every 8 hours for 2 to 7 days, then oral therapy for primary infection to complete 10 days

Oral: 400 mg three times daily for 5 days OR 800 mg twice daily for 5 days

ALL IV doses to be infused over 2 hours

20 mg/kg/dose IV Q8H x 14-21 days

Note: If limited to skin, eye and mucous membrane HSV infection, treat for minimum 14 days. If disseminated or CNS disease, treat for minimum duration of 21 days

< 32 wks GA or weight < 1200g≥ 32 wks GA and weight ≥ 1200g20 mg/kg/dose IV Q12H x 21 days20 mg/kg/dose IV Q8H x 21 days

< 32 wks GA or weight < 1200g≥ 32 wks GA and weight ≥ 1200g20 mg/kg/dose IV Q12H x 14 days20 mg/kg/dose IV Q8H x 14 days

< 32 wks GA or weight < 1200g≥ 32 wks GA and weight ≥ 1200g15 mg/kg/dose IV Q12H x 10 to 14 days15 mg/kg/dose IV Q8H x 10 to 14 days


Central LinePeripheral Line7 mg/mL5 mg/mL

7 mg/mL5 mg/mLMix 8.6 mL of D5W with 1.4 mL of 50 mg/mL Acyclovir in a 10mL empty sterile vial = 7 mg/mLMix 9 mL of D5W with 1 mL of 50 mg/mL Acyclovir in a 10 mL empty sterile vial = 5 mg/mL

50 mg/mL = 24H 7 mg/mL = 24H 5 mg/mL = 24HStore at Room Temperature Do not refrigerate

Serum creatinine 90-109 micromole/LSerum creatinine 110-130 micromole/LSerum creatinine >130 micromole/L or urine output <1 ml/kg/h20 mg/kg/dose Q12H20 mg/kg/dose Q24H10 mg/kg/dose Q24H

General Information

Therapy and prophylaxis for herpes viral infections


  • Compatible in all stages of pregnancy, no untoward effects reported


  • Compatible

Follow SCr as appropriate, check urine for crystals if suspect AKI

  • GI upset, phlebitis - common

  • Increased SCr

  • AKI from crystal nephropathy

May diminish efficacy of varicella vaccine.

People taking long-term antiviral therapy should discontinue these drugs, if possible, at least 24 hours before administration of varicella vaccine and should not restart antiviral therapy until 14 days after vaccination.

Oral: 200 mg tablets IV: 500 mg vials

For oral indications, consider valacyclovir (pro-drug) which is more bioavailable with more convenient dosing.

Keep well hydrated to prevent nephrotoxicity from crystallization in renal tubules.

Dosage adjustment required in renal impairment, consult pharmacy.

Use adjusted body weight for calculating IV doses in obese patients.

Antimicrobial class: Antiviral, nucleoside analogue

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