Aciclovir Uses, Dosage, Side Effects, Food Interaction and all others data.

Aciclovir is a synthetic purine neucleotide analogue, which acts against human herpes viruses. The enzyme thymidine kinase (TK)encoded by HSV, VZV and EBV converts acyclovir into acyclovir monophosphate, a neucleotide analogue, which is further converted to diphosphate and triphosphate by cellular enzymes. Aciclovir triphosphate interferes with DNA polymerase and inhibits viral DNA replication with resultant chain termination following its incorporation into the growing viral DNA chain.

Aciclovir exerts its antiviral effect on herpes simplex viruses (HSV) and varicella-zoster virus by interfering with DNA synthesis and inhibiting viral replication. The exact mechanisms of action against other susceptible viruses have not fully elucidated. In vitro studies with herpes simplex viruses indicate that acyclovir triphosphate is the pharmacologically active form of the drug; the triphosphate functions as both a substrate for and preferential inhibitor of viral DNA polymerase.

Aciclovir is a synthetic purine nucleoside with inhibitory activity against herpes simplex virus(HSV-1 & HSV-2) and varicella-zoster virus (VZV). The activity of Aciclovir is highly selective due to its affinity for the enzyme thymidine kinase encoded by HSV and VZV. This viral enzyme converts Aciclovir into Aciclovir monophosphate, a nucleotide analogue. The monophosphate is further converted into diphosphate and finally triphosphate by a number of cellular enzymes. In vitro, Aciclovir triphosphate stops replication of herpes viral DNA. This is accomplished in 3 ways: 1) Competitive inhibition of viral DNA polymerase, 2) Incorporation into and termination of the growing viral DNA chain and 3) Inactivation of the viral DNA polymerase.

Trade Name Aciclovir
Availability Prescription only
Generic Acyclovir
Acyclovir Other Names Aciclovir, Aciclovirum, Acycloguanosine, Acyclovir
Related Drugs prednisone, valacyclovir, Valtrex, Zovirax, Deltasone, tetracaine topical, famciclovir, lysine, benzocaine topical, Abreva
Weight 200mg,
Type Tablet
Formula C8H11N5O3
Weight Average: 225.2046
Monoisotopic: 225.086189243
Protein binding

Acyclovir is 9-33% protein bound in plasma.

Groups Approved
Therapeutic Class Anti Viral
Manufacturer R,y, International, Ranbaxy (uk) Limited A Sun Pharmaceutical Company
Available Country Pakistan, United Kingdom, Netherlands
Last Updated: September 19, 2023 at 7:00 am


Aciclovir IV for Infusion is used for the treatment of- Herpes Zoster, Genital Herpes, Chickenpox, Herpes Simplex Infections, Herpes Simplex Encephalitis

Aciclovir eye ointment is used for treatment of Herpes Simplex Keratitis.

Aciclovir Oral is used for Herpes Zoster Genital Herpes, Chickenpox, Herpes Simplex Infections, Herpes Simplex Encephalitis

Aciclovir cream are used for the treatment of herpes simplex virus infections of the skin including initial and recurrent genital herpes and herpes labialis.

Aciclovir is also used to associated treatment for these conditions: Bell's Palsy, Chickenpox, Cytomegalovirus (CMV) Infection, Encephalitis, Herpes Simplex, Herpes Simplex Infection, Herpes Zoster, Herpes simplex of the oral-labial, Herpes simplex type I reactivation, Recurrent Genital Herpes (RGH), Recurrent Herpes Labialis, VZV re-activation, Acute Genital herpes, Acute Herpes labialis, Acute Herpetic keratitis, Severe Genital herpes

How Aciclovir works

Aciclovir is becomes acyclovir monophosphate due to the action of viral thymidine kinase. Aciclovir monophosphate is converted to the diphosphate form by guanylate kinase. Aciclovir diphosphate is converted to acyclovir triphosphate by nucleoside diphosphate kinase, pyruvate kinase, creatine kinase, phosphoglycerate kinase, succinyl-CoA synthetase, phosphoenolpyruvate carboxykinase and adenylosuccinate synthetase. Aciclovir triphosphate has higher affinity for viral DNA polymerase than cellular DNA polymerase and incorporates into the DNA where the missing 2' and 3' carbons causes DNA chain termination. In other cases acyclovir triphosphate competes so strongly for viral DNA polymerase that other bases cannot associate with the enzyme, inactivating it.


Aciclovir dosage

Apply ointment into lower conjunctival sac five times daily at 4 hours interval; continue for minimum 3 days after healing.

Aciclovir cream should be applied to lesions or impending lesions 5 times daily (at 4 hourly intervals omitting the night-time dose). Treatment should continue for 5 days. If healing does not occur, treatment may be extended for up to 10 days.

The total daily dosage of Aciclovir should be based on the type or severity of infection and given in equally divided doses based on consideration of degree of susceptibility of the pathogens, renal function and body-weight.

Aciclovir Tablet

• Acute Herpes Zoster:

800 mg every 4 hours, 5 times daily for 7 to 10 days.

• Genital Herpes:

Initial Genital Herpes: 200 mg every 4 hours, 5 times daily for 10 days.

Chronic suppressive therapy for recurrent disease: 400 mg 2 times daily for up to 12 months.

Intermittent therapy: 200 mg every 4 hours, 5 times daily for 5 days.

• Chickenpox:

Children (2 years of age and older): 20 mg/kg/dose 4 times daily (80 mg/kg/day) for 5 days.

Adults and Children (>40 kg): 800 mg 4 times daily for 5 days.

Aciclovir IV

The required dose of Aciclovir IV should be administered by slow intravenous infusion over a one-hour period.

• Herpes Simplex (HSV-1 and HSV-2) Infections:

Adults and Adolescents (≥12 years): 5 mg/kg, 8 hourly for 7 days.

Pediatrics (<12 years): 10 mg/kg 8 hourly for 7 days.

• Severe Initial Herpes Genitalis:

Adults and Adolescents (≥12 years): 5 mg/kg 8 hourly for 5 days.

• Herpes Simplex Encephalitis:

Adults and Adolescents (≥12 years): 10 mg/kg 8 hourly for 10 days.

Pediatrics (3 months to 12 years of age): 20 mg/kg 8 hourly for 10 days.

• Neonatal Herpes Simplex (Birth to 3 months):

10 mg/kg 8 hourly for 10 days.

• Varicella Zoster:

Adults and Adolescents (≥12 years): 10 mg/kg 8 hourly for 7 days.

Pediatrics (<12 years): 20 mg/kg 8 hourly for 7 days.

Dose adjustment of Tablet for patients with acute or chronic renal impairment, based on Creatinine Clearance, Cr Cl (mL/min/1.73 m2):

For Cr Cl= > 25 : 800 mg 4 hourly 5 times daily

For Cr Cl = 10 to 25 : 200 mg 4 hourly 5 times daily or 400 mg 12 hourly or 800 mg 8 hourly

For Cr Cl = 0 to 10 : 200 mg 12 hourly or 400 mg 12 hourly or 800 mg 12 hourly

Dose adjustment of IV for patients with acute or chronic renal impairment, based on Creatinine Clearance, Cr Cl (mL/min/1.73 m2):

For Cr Cl = > 50 : 100% of recommended dose, 8 hourly

For Cr Cl = 25 to 50 : 100% of recommended dose, 12 hourly

For Cr Cl = 10 to 25 : 100% of recommended dose, 24 hourly

For Cr Cl = 0 to 10 : 50% of recommended dose, 24 hourly

Caution: Rapid or bolus intravenous injection must be avoided. Intramuscular or subcutaneous injection must be avoided.

Reconstitution procedure of IV infusion

Vial containing 250 mg Aciclovir will be reconstituted with 50 ml infusion solution and vial containing 500 mg Aciclovir will be reconstituted with 100 ml infusion solution. Besides, Vial containing 1 gm Aciclovir will be reconstituted with 250 ml infusion solution. 10 ml of the infusion solution will be added to the vial containing 250 mg, 500 mg and 1 gm Aciclovir. Shake well and transfer the required amount of solution to the infusion container. The final concentration of Aciclovir will be not more than 5 mg/ml.

The reconstituted solution should be used within 12 hours. Refrigeration of reconstituted solution may result in the formation of a precipitate which will re-dissolve at room temperature.

Compatible infusion fluids

Sodium Chloride Intravenous Infusion BP (0.45% and 0.9% w/v)

Sodium Chloride (0.18% w/v) and Glucose (4% w/v) Intravenous Infusion BP

Sodium Chloride (0.45% w/v) and Glucose (2.5% w/v) Intravenous Infusion BP

Hartmann's Solution

It is recommended that Aciclovir IV Injection for Intravenous Infusion should be administered for five to seven days in the treatment of most infections and for at least ten days in the treatment of Herpes simplex encephalitis.

Each 250 mg vial of Aciclovir IV Injection should be reconstituted by the addition of 10 ml of either Water for Injection or Sodium Chloride Intravenous Infusion (0.9% w/v). This provides a solution containing 25 mg Aciclovir per ml.

Each 500 mg vial of Aciclovir IV Injection should be reconstituted by the addition of 10 ml of either Water for Injection or Sodium Chloride Intravenous Infusion (0.9% w/v). This provides a solution containing 50 mg Aciclovir per ml.

Side Effects

Transient mild stinging immediately following application may occur in a small proportion of patients. Local irritation and inflammation such as blepharitis and conjunctivitis have also been reported.

Skin rashes which, resolve after withdrawal of the drug have been reported with acyclovir. The most common adverse effect is mild pain including transient burning and stinging at the site of application following acyclovir cream.


Symptoms of overdose include agitation, coma, seizures, lethargy, and precipitation in renal tubules. These symptoms are more common in patients given high doses without monitoring of fluid and electrolyte balance or reduced kidney function. In the case of an overdose, treat with symptomatic and supportive care.


Aciclovir should be administered with caution in patient with renal impairment and doses should be adjusted according to creatinine clearance.

Renal impairment. Pregnancy, lactation. Neurological abnormalities with significant hypoxia, serious hepatic or electrolyte abnormalities. Maintain adequate hydration.

Aciclovir cream is not recommended for application to mucous membrane such as eye, mouth, vagina etc.


Concomitant administration of probenecid and acyclovir has reportedly increased the mean plasma half-life and decreased urinary excretion and renal clearance of acyclovir. Amphotericin B has been shown to potentiate the antiviral effect of acyclovir against pseudorabies virus in vitro when both drugs are added to the culture medium. Ketoconazole and acyclovir have shown dose-dependent, synergistic, antiviral activity against herpes simplex virus types 1 and 2 (HSV-1 and HSV-2) in in-vitro replication studies.

Food Interaction

  • Drink plenty of fluids. Dehydration with acyclovir predisposes patients to nephrotoxicity.
  • Take with or without food. The absorption is unaffected by food.

Volume of Distribution

The volume of distribution of acyclovir is 0.6L/kg.

Elimination Route

The oral bioavailability of acyclovir is 10-20% but decreases with increasing doses. Aciclovir ointment is 12 Aciclovir buccal tablets and ophthalmic ointment are minimally absorbed. The bioavailability of acyclovir is not affected by food.

Aciclovir has a mean Tmax of 1.1±0.4 hours, mean Cmax of 593.7-656.5ng/mL, and mean AUC of 2956.6-3102.5h*ng/mL.

Half Life

The clearance of acyclovir varies from 2.5-3 hours depending on the creatinine clearance of the patient. The plasma half life of acyclovir during hemodialysis is approximately 5 hours. The mean half life in patients from 7 months to 7 years old is 2.6 hours.


The renal clearance of acyclovir is 248mL/min/1.73m. The total clearance in neonates if 105-122mL/min/1.73m

Elimination Route

The majority of acyclovir is excreted in the urine as unchanged drug. 90-92% of the drug can be excreted unchanged through glomerular filtration and tubular secretion. 2.

Pregnancy & Breastfeeding use

Pregnancy category B. There are no adequate and well-controlled studies in pregnant women. Aciclovir should be used during pregnancy only if the potential benefit justifies the potential risk to the fetus.

Use in nursing mothers: Aciclovir should be administered to a nursing mother with caution and only when indicated. Geriatric Use: No overall differences in safety are observed between older and younger subjects.

The use of Aciclovir sterile eye ointment should be considered only when the potential benefits outweigh the possibility of unknown risk.


Aciclovir IV Injection is contraindicated in patients known to be hypersensitive to Aciclovir or Valacyclovir.

Aciclovir ophthalmic is contraindicated to the patients with known hypersensitivity to acyclovir.

Aciclovir oral is contraindicated in patients known to be hypersensitive to acyclovir. For the patients with severe renal impairment, a reduction of the doses is recommended.

Aciclovir cream is contraindicated in patients known to be hypersensitive to acyclovir.

Special Warning

The dose of Aciclovir IV injection in children aged 1-12 years should be calculated on the basis of body surface area. Children in this age group with Herpes simplex infections (except Herpes simplex encephalitis) or Varicella zoster infections should be given Aciclovir Infusion in doses of 250 mg per square metre of body surface area (equivalent to 5 mg/kg in adults). Immunocompromised children in this age group with Varicella zoster virus infection or with Herpes simplex encephalitis should be given Aciclovir IV Infusion in doses of 500 mg per square metre of body surface area (equivalent to 10 mg/kg in adults). Children with impaired renal function require an appropriately modified dose, according to the degree of impairment.

HSV infections in children over 2 years should be given adult doses and children below 2 years should be given half of the adult dose.

Acute Overdose

Symptoms: Elevations in BUN and serum creatinine, subsequent renal failure, anuria, agitation, coma, lethargy, seizures.

Management: Consider use of haemodialysis until renal function is restored.

Interaction with other Medicine

Probenecid reduces Aciclovir excretion and so increases plasma concentration and risk of toxicity.

Storage Condition

Store at 15°C to 25°C. Protected from light and moisture. Keep the medicine out of the reach of children.

Innovators Monograph

You find simplified version here Aciclovir

Aciclovir contains Acyclovir see full prescribing information from innovator Aciclovir Monograph, Aciclovir MSDS, Aciclovir FDA label


What is Aciclovir used for?

It is primarily used for the treatment of herpes simplex virus infections, chickenpox, and shingles. Other uses include prevention of cytomegalovirus infections following transplant and severe complications of Epstein–Barr virus infection.

How safe is Aciclovir?

It is concluded that long-term suppression with Aciclovir is safe and effective for patients with recurrent genital herpes.

How does Aciclovir work?

Aciclovir works by stopping the spread of the herpes virus in the body.

What are the common side effects of Aciclovir?

Common side effects of Aciclovir may include:

  • mild skin pain;
  • rash, itching;
  • nausea, vomiting, diarrhea;
  • headache; or.
  • mouth pain while using an acyclovir buccal tablet.

Is Aciclovir safe during pregnancy?

Use of Aciclovir in the first trimester does not increase birth defects, and it should be the antiviral drug of choice in early pregnancy.

Is Aciclovir safe during breastfeeding?

Aciclovir to be safe during breastfeeding.

Can I drink alcohol with Aciclovir?

Yes, you can drink alcohol while taking Aciclovir.

Can I drive after taking Aciclovir?

This Aciclovir may rarely make you dizzy. Alcohol or marijuana (cannabis) can make you more dizzy. Do not drive, use machinery, or do anything that needs alertness until you can do it safely.

When should be taken of Aciclovir?

Aciclovir treatment is best started within 72 hours of symptom onset (ie, rash, blisters, tingling, burning) and most effective if started within 48 hours of symptom onset.

How often can I take Aciclovir ?

The tablets, capsules, and suspension are usually taken two to five times a day for 5 to 10 days, starting as soon as possible after your symptoms begin.

Can I take Aciclovir on an empty stomach?

You should take Aciclovir with or without food.

How long does Aciclovir take to work?

Aciclovir begins to work within 24 to 48 hours after you start taking it.

How long does Aciclovir take to work?

Aciclovir has a half-life of 2.5 to 3.3 hours in people with normal renal function.

How long can I take Aciclovir for a long time?

Long-term use of Aciclovir for up to 10 years for HSV suppression is effective and well tolerated.

Who should not take Aciclovir?

You should not take Aciclovir if you are allergic to milk proteins. Tell your doctor if you have ever had: kidney disease; or. a weak immune system (caused by disease or by using certain medicine).

What happen If I missed dose of Aciclovir?

If you miss a dose of Aciclovir take it as soon as possible, then just carry on with your regular dosing schedule. If you remember your missed dose close to the time for your next dose (ie. within 2 hours), do not double your dose.

What happen if I overdose on Aciclovir?

Taking too much Aciclovir by accident is unlikely to harm you, unless you take too much over several days. Talk to your doctor or pharmacist if you're worried that you have had too much Aciclovir.

What happen If I suddenly stop taking Aciclovir?

If you stop taking the drug suddenly or don't take it at all: The symptoms of your infection may not get better or may get worse. If you miss doses or don't take the drug on schedule: Your medication may not work as well or may stop working completely.

Can Aciclovir make me infertile?

There are no known effects of Aciclovir treatment on fertility or conception rate.

Can Aciclovir cause heart palpitations?

Increased heart rate (tachycardia).

Can Aciclovir affects my heart ?

Aciclovir can present in clinical practice as acute kidney injury (AKI), crystal-induced nephropathy, acute tubulointerstitial nephritis, and rarely, as tubular dysfunction.

Does Aciclovir cause liver damage?

No instances of acute liver failure or chronic liver injury have been linked to Aciclovir use. The liver injury associated with Aciclovir is usually mild and resolves rapidly.

*** Taking medicines without doctor's advice can cause long-term problems.