Acyclovir

Classification of Acyclovir

Acyclovir, also known as aciclovir or acycloguanosine, is an antiviral medicine from the nucleoside analogue class. It is mainly active against herpes family viruses and is considered a guanosine analogue that becomes active after conversion inside infected cells.

Information about Acyclovir

Acyclovir was developed as one of the first highly selective antiviral medicines for herpesvirus infections. Its selectivity stems from its greater activation in virus-infected cells than in healthy cells.

The chemical formula of acyclovir is C8H11N5O3. Chemical Structure of Acyclovir: insert a high-quality structure image with attribution from DrugBank or PubChem.

Pharmacology of Acyclovir

After oral dosing, acyclovir has relatively low bioavailability, averaging 10-20%, and this decreases as the dose increases. It reaches peak blood levels typically within about 1 to 2 hours. Plasma protein binding is low to moderate, around 9 to 33 percent.

The plasma elimination half-life in adults with normal kidney function is about 2.5 to 3.3 hours, but it can become much longer in renal impairment. Acyclovir is cleared mainly by the kidneys through glomerular filtration and tubular secretion, so dose adjustments are commonly required when kidney function is reduced.

It is available in multiple dosage forms, including oral tablets and suspension, intravenous infusion, topical cream or ointment, and ophthalmic formulations in some markets.

Uses of Acyclovir

• Treatment of herpes simplex virus infections, including oral herpes such as cold sores and genital herpes
• First episode of genital herpes and recurrent genital herpes management as advised by a clinician
• Suppressive therapy to reduce the frequency of recurrent genital herpes outbreaks in selected patients
• Treatment of varicella zoster virus infections, such as shingles, especially when started early
• Treatment of chickenpox in selected patients, particularly those at higher risk of complications
• Treatment and prevention of herpes infections in immunocompromised patients under specialist care
• Treatment of herpes simplex encephalitis and neonatal herpes using intravenous acyclovir in hospital settings

How Acyclovir works

• Acyclovir is a prodrug-like antiviral that becomes active mainly inside infected cells
• Viral thymidine kinase converts acyclovir into acyclovir monophosphate, then human enzymes convert it into the active triphosphate form
• Acyclovir triphosphate selectively inhibits viral DNA polymerase more than human DNA polymerase
• It can get incorporated into viral DNA and causes chain termination, stopping the virus from making new DNA copies
• This reduces viral replication, helps lesions heal faster, and lowers viral shedding when used correctly
• Effectiveness is best when started early in an outbreak, and dosing timing matters because the drug is cleared quickly
• Kidney function and hydration status influence safety, especially with higher doses or IV therapy

Side effects of Acyclovir

• Common side effects
  • Nausea, vomiting, diarrhea, abdominal discomfort
  • Headache, dizziness, tiredness
  • Rash or itching in some patients
• Side effects are seen more with IV acyclovir or higher exposure
  • Kidney-related problems, especially if dehydrated or with pre-existing kidney disease
  • Local irritation or inflammation at the IV site
• Less common but serious side effects that need urgent medical attention
  • Signs of allergic reaction, such as facial swelling, severe rash, or breathing difficulty
  • Confusion, agitation, tremors, hallucinations, or seizures, more likely with kidney impairment or high doses
  • Reduced urine output, severe flank pain, or sudden swelling, which may suggest kidney injury
• When to seek medical help
  • If you develop a severe headache with confusion, seizures, unusual behavior changes, or fainting
  • If you notice signs of kidney trouble, such as very low urine output or severe dehydration
  • If you have a widespread rash, blistering, or any breathing difficulty

Disclaimer for Acyclovir

This content is for informational and educational purposes only and should not replace professional medical advice. Always consult a qualified healthcare provider before starting, stopping, or changing any medication.