ZOVIRAX 200/MG/5/ML SUSP

Indications

Approved Uses

Treatment of herpes simplex infections of skin and mucous membranes (including genital herpes) and varicella-zoster infections (chickenpox and herpes zoster); in some labeling also includes HSV encephalitis and neonatal HSV (often managed with IV acyclovir rather than oral suspension).

Off-Label Uses

HSV/VZV prophylaxis in selected immunocompromised patients (e.g., some transplant/hematology settings) is used; CMV prophylaxis is generally not preferred (valganciclovir/ganciclovir are standard) and acyclovir is only used in limited/low-risk protocols; EBV treatment is not routinely recommended (limited clinical benefit).

Dosage & Administration

Dosing by Condition

HSV (genital/mucocutaneous) initial episode: 200 mg 5 times daily for 10 days (alternative: 400 mg 3 times daily for 7-10 days). Recurrent genital HSV: 200 mg 5 times daily for 5 days (alternative regimens exist). Suppression: 400 mg twice daily (or 200 mg 3-5 times daily). Herpes zoster: 800 mg 5 times daily for 7 days. Varicella (chickenpox): adults 800 mg 4 times daily for 5 days; children ≥2 years: 20 mg/kg (max 800 mg) 4 times daily for 5 days.

Initial Dose

Genital Herpes - Initial treatment: 200 mg orally every 4 hours while awake (5 times daily) for 10 days or 400 mg orally every 8 hours for 7-10 days

Maintenance Dose

For suppression of recurrent genital herpes: 400 mg twice daily for up to 12 months.

Maximum Dose

Maximum typical oral adult daily dose: 4,000 mg/day (e.g., 800 mg five times daily).

Children's Dosage

Chickenpox (2-18 years, <40kg): 20mg/kg (max 800mg per dose) 4 times daily for 5 days. Chickenpox (>40kg): adult dose 800mg 4 times daily for 5 days. HSV treatment in children: 250mg/m² or 5mg/kg every 8 hours (IV); oral dosing 200mg 4-5 times daily for children over 2 years. Neonatal herpes: IV acyclovir preferred

Dose Adjustment Notes

Dose adjustment is required in renal impairment (reduce dose and/or extend interval based on creatinine clearance); maintain adequate hydration; no routine hepatic dose adjustment is required.

How to Take

Shake well before each dose; measure with an oral syringe/medicine spoon; may be taken with or without food; space doses evenly (e.g., 5 times daily about every 4 hours while awake); maintain adequate hydration; complete the prescribed course.

How to Prepare

Ready-to-use oral suspension; shake well before each dose and measure with an appropriate dosing device.

Side Effects

Common Side Effects

Nausea, vomiting, diarrhea, headache; sometimes abdominal pain and rash (less common).

Side Effect Frequency

Common: nausea, vomiting, diarrhea, headache; less common/rare: rash/urticaria, reversible renal impairment (especially with dehydration/high doses), and neurotoxicity (confusion, hallucinations, seizures) particularly in renal impairment; severe hypersensitivity (e.g., anaphylaxis, SJS/TEN) is rare.

Safety & Warnings

Contraindications

Hypersensitivity to acyclovir, valacyclovir, or any excipients/components of the formulation.

Warnings & Precautions

Maintain adequate hydration; use caution and adjust dose in renal impairment; increased risk of renal and CNS toxicity in elderly and renally impaired-monitor renal function in high-risk patients; avoid/monitor with concomitant nephrotoxins; rare TTP/HUS in severely immunocompromised patients.

Age Restriction

Safety/efficacy for oral acyclovir are not established in children <2 years for most labeled oral indications; use in neonates/young infants is typically IV (specialist-directed) rather than this oral suspension.

Drug Interactions

Drug Interactions

Key interactions: probenecid and cimetidine (increase acyclovir exposure by reducing renal clearance); other nephrotoxic drugs (e.g., aminoglycosides, cyclosporine, tacrolimus) increase renal toxicity risk; mycophenolate mofetil may increase exposure of both; zidovudine may increase CNS adverse effects (e.g., lethargy/somnolence).

Interaction Severity

MAJOR/clinically significant: concomitant nephrotoxic agents (e.g., aminoglycosides, cyclosporine, tacrolimus, amphotericin B, IV contrast, cidofovir) increase risk of renal toxicity; MODERATE: probenecid and cimetidine can increase acyclovir exposure by reducing renal tubular secretion; zidovudine may increase CNS adverse effects (e.g., lethargy/somnolence) in some patients.

Food Interaction

No clinically significant food interaction; may be taken with or without food.

Special Populations

Children

Chickenpox (2-18 years, <40kg): 20mg/kg (max 800mg per dose) 4 times daily for 5 days. Chickenpox (>40kg): adult dose 800mg 4 times daily for 5 days. HSV treatment in children: 250mg/m² or 5mg/kg every 8 hours (IV); oral dosing 200mg 4-5 times daily for children over 2 years. Neonatal herpes: IV acyclovir preferred

Kidney Impairment

Adjust dose/interval in renal impairment. For 200 mg five-times-daily regimen: CrCl 10-25 mL/min: 200 mg every 8 hours; CrCl <10 mL/min: 200 mg every 12 hours. For 800 mg five-times-daily regimen: CrCl 10-25 mL/min: 800 mg every 8 hours; CrCl <10 mL/min: 800 mg every 12 hours.

Storage & Patient Advice

Preparation Instructions

Ready-to-use oral suspension; shake well before each dose and measure with an appropriate dosing device.

Missed Dose

Take the missed dose as soon as remembered; if it is close to the next scheduled dose, skip the missed dose and resume the regular schedule; do not double doses.

Stopping the Medicine

Complete the prescribed treatment course; do not stop early unless advised. For long-term suppressive therapy, reassess periodically with the prescriber (commonly around 6-12 months) before discontinuation.

Overdose

Symptoms may include nausea/vomiting, headache, agitation/confusion/hallucinations, seizures, and acute kidney injury (elevated creatinine/renal failure), especially with dehydration or renal impairment; management is supportive with aggressive hydration, monitoring renal/neurologic status, and hemodialysis can enhance removal in severe cases-seek urgent medical care.

Patient Counseling

Shake well and measure doses accurately; take at evenly spaced intervals and complete the course; maintain good hydration; may take with or without food; this reduces severity/duration but does not eradicate HSV or fully prevent transmission; seek care for reduced urination, severe rash, or confusion; store below 30°C (per SFDA verified storage condition).

Monitoring Requirements

Monitor renal function (serum creatinine/CrCl; BUN as supportive) in patients with renal impairment, elderly, high-dose therapy, dehydration risk, or concomitant nephrotoxins; monitor for neurotoxicity (confusion, tremor, hallucinations) in at-risk patients.

Pharmacology

Mechanism of Action

Acyclovir is a guanosine nucleoside analogue activated by viral thymidine kinase to monophosphate then by host kinases to triphosphate; acyclovir triphosphate competitively inhibits viral DNA polymerase and is incorporated into viral DNA causing chain termination.

Onset of Action

Pharmacologic activity begins after absorption (peak levels typically ~1.5-2 hours after an oral dose); clinical symptom improvement is usually seen over 1-3 days when started early.

Duration of Effect

Short duration requiring frequent dosing: oral acyclovir half-life is ~2-3 hours in normal renal function, so therapeutic effect is maintained only with repeated dosing (e.g., every ~4 hours while awake for 5-times-daily regimens).

Half-Life

Approximately 2.5-3.3 hours in adults with normal renal function; markedly prolonged in severe renal impairment/ESRD (can approach ~20 hours).

Bioavailability

Approximately 10-30% oral bioavailability (low and decreases with increasing dose).

Metabolism

Minimal metabolism; a small fraction is converted to the inactive metabolite 9-carboxymethoxymethylguanine (CMMG).

Excretion

Primarily renal elimination via glomerular filtration and active tubular secretion; most of the dose is excreted unchanged in urine (commonly cited ~60-90%).

Protein Binding

Low protein binding: about 9-33% (often cited ~15%).

Product Information

Available Dosage Forms

Oral suspension, tablet, powder for intravenous infusion, topical cream, ophthalmic ointment

Composition per Dose

Each 5ml: 200mg acyclovir (as acyclovir base)

Generic Availability

Yes

OTC Alternatives

No OTC oral antiviral alternative; topical acyclovir 5% cream is OTC in some countries for herpes labialis, but availability is jurisdiction-specific and not an OTC substitute for systemic therapy.

Viral Target

Herpes

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