Aciclovir is a nucleoside analogue antiviral medication specifically designed to inhibit the replication of herpes viruses. It is widely recognized in clinical practice for its efficacy in managing outbreaks of herpes simplex virus (HSV-1, HSV-2) and varicella-zoster virus (VZV). By targeting viral DNA polymerase, aciclovir disrupts the viral replication process, reducing symptom severity, accelerating healing, and decreasing the frequency of recurrences. This medication is available in multiple formulations—oral tablets, topical cream, and intravenous infusion—to accommodate varying clinical needs and infection severities.

Features

• Active ingredient: Aciclovir (chemically known as 2-amino-1,9-dihydro-9-[(2-hydroxyethoxy)methyl]-6H-purin-6-one)
• Mechanism of action: Selective inhibition of viral DNA polymerase via phosphorylation by viral thymidine kinase
• Formulations: 200mg, 400mg, 800mg oral tablets; 5% topical cream; intravenous solution (500mg/10mL vial)
• Bioavailability: Approximately 15–30% for oral administration; significantly higher with IV formulation
• Half-life: 2.5–3.3 hours in adults with normal renal function
• Excretion: Primarily renal, with ~80% excreted unchanged in urine

Benefits

• Reduces duration and severity of active herpes outbreaks
• Decreases frequency of recurrent episodes with prophylactic use
• Lowers risk of viral transmission to susceptible individuals
• Minimizes complications such as neurologic involvement or disseminated infection
• Supports faster healing of lesions and symptom relief
• Available in multiple administration routes for tailored treatment

Common use

Aciclovir is indicated for the treatment of initial and recurrent episodes of herpes simplex virus infections (genital herpes, cold sores, herpetic whitlow), herpes zoster (shingles), and chickenpox. It is also used prophylactically to prevent recurrence in immunocompromised patients (e.g., HIV/AIDS, chemotherapy recipients, transplant patients) and for suppression in individuals with frequent genital herpes outbreaks.

Dosage and direction

Dosage varies based on infection type, patient immune status, and formulation:

• Genital herpes (initial episode): 200mg orally every 4 hours (5x daily) for 10 days, or 400mg TID for 7–10 days
• Recurrent genital herpes: 200mg every 4 hours (5x daily) for 5 days; alternative: 400mg TID for 5 days
• Chronic suppression: 400mg BID or 200mg TID–QID; may adjust based on recurrence frequency
• Herpes zoster: 800mg orally every 4 hours (5x daily) for 7–10 days
• Chickenpox (immunocompetent patients): 20mg/kg (max 800mg) QID for 5 days
• Topical cream: Apply to affected area every 3–4 hours (6x daily) for 7 days
• IV dosing: 5–10mg/kg every 8 hours, infused over 1 hour; adjust for renal impairment

Take oral doses with plenty of water to ensure adequate renal clearance.

Precautions

• Renal function must be assessed before and during treatment; dosage adjustment required for creatinine clearance <50mL/min
• Maintain adequate hydration to prevent crystalline nephropathy
• Use with caution in elderly patients due to age-related decline in renal function
• Neurologic symptoms (e.g., agitation, confusion) should be monitored, especially with IV administration
• Topical formulation is for external use only; avoid contact with eyes and mucous membranes
• Not a cure for herpes infections; does not eliminate latent virus or prevent transmission entirely

Contraindications

• Hypersensitivity to aciclovir, valaciclovir, or any component of the formulation
• Severe renal impairment (CrCl <10mL/min) without appropriate dose adjustment and monitoring
• Concurrent use of other nephrotoxic agents without close supervision (e.g., aminoglycosides, cyclosporine)

Possible side effect

Common:

• Nausea, vomiting, diarrhea
• Headache, dizziness
• Mild skin reactions (rash, pruritus)

Less common:

• Elevated liver enzymes, jaundice
• Renal impairment (especially with dehydration or IV use)
• Neurologic effects: confusion, hallucinations, tremors (more frequent with high-dose IV)
• Hematologic changes: leukopenia, thrombocytopenia
• Local reactions: phlebitis (IV), burning/stinging (topical)

Drug interaction

• Probenecid: Reduces renal clearance of aciclovir, increasing plasma levels and risk of toxicity
• Nephrotoxic agents (e.g., aminoglycosides, NSAIDs, cyclosporine): Increased risk of renal impairment
• Zidovudine: Potential for enhanced neurotoxicity (lethargy, fatigue)
• Mycophenolate mofetil: Possible increased levels of both drugs

Missed dose

If a dose is missed, take it as soon as remembered unless it is nearly time for the next dose. Do not double the dose to make up for a missed one. Maintain regular dosing intervals to ensure consistent antiviral activity.

Overdose

Symptoms may include agitation, coma, seizures, and renal impairment. Management involves supportive care and hemodialysis (which significantly enhances aciclovir clearance). Maintain adequate hydration and monitor renal function closely.

Storage

• Store tablets and cream at room temperature (15–30°C), away from moisture and light
• Keep IV solution refrigerated (2–8°C); use reconstituted solution within 12 hours
• Keep all formulations out of reach of children

Disclaimer

This information is intended for educational purposes and does not replace professional medical advice. Dosage and treatment decisions must be made by a qualified healthcare provider based on individual patient characteristics. Always follow prescribed instructions and report any adverse effects promptly.

Reviews

Clinical studies and meta-analyses consistently demonstrate aciclovir’s efficacy in reducing herpes outbreak duration and frequency. A Cochrane review of 26 trials confirmed that aciclovir shortens healing time and symptom duration in recurrent genital herpes by approximately 1–2 days. Long-term suppressive therapy has shown up to 80% reduction in recurrence rates. Topical formulations are generally considered less effective than systemic administration for moderate to severe episodes but remain useful for mild localized outbreaks. Patient tolerance is generally high, with most adverse effects being mild and transient.