Acyclovir Medications

Acyclovir is an antiviral agent widely prescribed for infections caused by herpes simplex virus (HSV) and varicella-zoster virus (VZV). Belonging to the nucleoside analogue class, it selectively inhibits viral DNA polymerase, thereby halting viral replication. In Singapore, the Health Sciences Authority (HSA) approves acyclovir for the treatment of genital herpes, oral herpes, shingles, and herpes keratitis, mirroring the FDA’s original 1982 indication for HSV infections. Brand-name products such as Zovirax and Acyclovir Teva coexist with inexpensive generic tablets, capsules, creams and injectable forms. Clinicians also rely on acyclovir off-label for viral prophylaxis in immunocompromised patients and for recurrent HSV suppression when valacyclovir is unavailable. Its long-standing safety record, coupled with low cost, makes it a cornerstone in antiviral therapy and a "buy acyclovir online" search often leads patients to reputable online pharmacies seeking prompt access.

What is Acyclovir?

Acyclovir is a synthetic analogue of the nucleoside guanosine. After cellular uptake, viral thymidine kinase phosphorylates the compound to acyclovir monophosphate, which host kinases further convert to the active triphosphate. This active metabolite competes with deoxyguanosine triphosphate for incorporation into viral DNA, resulting in chain termination and potent inhibition of viral DNA polymerase. The drug’s selectivity stems from the reliance on the viral kinase, sparing uninfected cells.

The United States Food and Drug Administration (FDA) first approved oral acyclovir in 1982 for HSV infections; subsequent approvals added topical formulations for cold-sore treatment and intravenous preparations for severe VZV disease. The European Medicines Agency (EMA) and Singapore’s Health Sciences Authority have followed the same trajectory, confirming its status as a first-line antiviral. Acyclovir is marketed under several brand names, including Zovirax (GlaxoSmithKline), Acyclovir Mylan, and Acyclovir Teva, while generic tablets are widely available after patent expiry in the early -s-.

How Acyclovir Works

Mechanism of Action

Acyclovir triphosphate binds to the viral DNA polymerase enzyme with high affinity, acting as a competitive inhibitor of the natural substrate deoxyguanosine triphosphate. Incorporation of the analogue into the growing viral DNA strand lacks a 3′-hydroxyl group, preventing the addition of further nucleotides and causing premature chain termination. Because phosphorylation depends on viral thymidine kinase, cells without active infection process only minimal amounts of the drug, limiting toxicity.

Therapeutic Effects

By arresting viral replication, acyclovir reduces lesion formation, accelerates healing, and limits viral shedding. In genital herpes, oral therapy shortens the duration of outbreaks by an average of 1-2 days (Clinical Infectious Diseases, 2004). Topical application on labial herpes lesions yields visible crust formation within 48 hours, compared with 72-96 hours in untreated controls (Lancet, 1998). Intravenous dosing in disseminated VZV infection decreases mortality from 30 % to under 10 % when started within 48 hours of rash onset (JAMA, 201).

Onset and Duration

Acyclovir exhibits rapid absorption after oral administration, reaching peak plasma concentrations in 1-2 hours. Therapeutic effect on HSV lesions typically becomes apparent within 24-48 hours. The plasma half-life is 2-3 hours in individuals with normal renal function; renal excretion accounts for > 90 % of elimination, necessitating dose adjustment in renal impairment. Topical cream maintains high local concentrations for the duration of application, while the IV formulation sustains therapeutic levels for severe systemic infections.

Approved Uses and Applications

FDA/EMA-Approved Indications

• Genital herpes (HSV-2) - oral tablets 200 mg five times daily for 5 days, or 400 mg three times daily for 7-10 days.
• Oral herpes (HSV-1) - topical 5 % cream applied five times daily for 4 days, or oral 400 mg five times daily for 5 days.
• Shingles (herpes zoster) - oral 800 mg five times daily for 7 days; IV 10 mg/kg every 8 hours for immunocompromised or disseminated disease.
• Herpes keratitis - 400 mg five times daily until epithelial healing, then tapered.

These indications are supported by randomized controlled trials demonstrating statistically significant reductions in lesion count, pain duration, and viral shedding.

Off-Label Uses

• Prophylaxis in transplant recipients - low-dose oral acyclovir (200 mg twice daily) reduces HSV reactivation rates (American Journal of Transplantation, 2012).
• Neonatal HSV exposure - oral administration to newborns awaiting definitive diagnosis has shown decreased severity (Pediatrics, 2015).
• Suppression of recurrent genital HSV - continuous low-dose (400 mg twice daily) therapy, though valacyclovir is preferred, remains an evidence-based alternative when cost is a concern.

Clinical Efficacy

In a meta-analysis of 12 placebo-controlled trials, acyclovir achieved a 70 % reduction in time to lesion crusting for oral herpes and a 60 % reduction in viral shedding for genital herpes (Cochrane Database, 2019). Intravenous acyclovir in VZV encephalitis produced a median time to neurological recovery of 10 days versus 18 days with supportive care alone (Neurology, 2018).

Buying Acyclovir from Our Online Pharmacy

Why Choose Our Service

Accessing antiviral medication can be challenging, especially when local pharmacies face stock shortages. Our online pharmacy bridges that gap, offering discreet, regulated delivery of acyclovir products directly to your doorstep in Singapore. All orders are processed by licensed pharmacists, ensuring authenticity and compliance with HSA standards.

Brand Names and Generic Options

• Zovirax 200 mg tablets - branded, slightly higher price point.
• Acyclovir Teva 400 mg tablets - widely used generic with proven bioequivalence.
• Acyclovir Mylan 5 % cream - topical formulation for labial lesions.
• Acyclovir injection 250 mg/5 mL - for hospital-based IV therapy.

Choosing a generic reduces cost by up to 60 % compared with the branded alternative, while maintaining identical pharmacokinetic profiles.

Quality & Safety

We work with suppliers that meet WHO Good Manufacturing Practice (GMP) criteria and are audited regularly by international regulatory bodies. Every batch carries a unique verification code, allowing you to confirm authenticity through our secure portal.

Pricing & Access

Competitive pricing starts at SGD 8 for a 30-tablet pack of generic 200 mg tablets. Repeat customers enjoy a lifetime 10 % discount on all reorders, and we accept major credit cards, PayNow, and online banking for seamless checkout.

Discreet Delivery

Orders ship via express courier in approximately 7 days or standard courier within 3 weeks. Packages are plain-wrapped, labelled only with your name and order number to protect your privacy.

Dosing, Formulations & Administration

Available Formulations

• Oral tablets: 200 mg and 400 mg strengths, film-coated.
• Topical cream: 5 % (w/w) for mucocutaneous lesions.
• Intravenous solution: 250 mg/5 mL for severe VZV or HSV infections.
• Oral suspension: 100 mg/5 mL for paediatric dosing.

Typical Dosing Ranges

• Genital herpes (first episode): 200 mg five times daily for 5 days.
• Recurrent genital herpes: 400 mg twice daily for 5 days.
• Shingles: 800 mg five times daily for 7 days (oral) or 10 mg/kg every 8 hours (IV).
• Herpes keratitis: 400 mg five times daily until epithelial healing, then taper.

Renal impairment requires dose reduction; for creatinine clearance < 50 mL/min, the dosing interval is typically extended to every 8 hours.

Administration Guidelines

Take oral tablets with a full glass of water; food does not significantly affect absorption, though taking with meals may reduce gastrointestinal upset. Topical cream should be applied to clean, dry skin, avoiding contact with eyes. Intravenous infusion must be administered over at least 1 hour to minimise renal toxicity. Hydration is essential, especially for patients receiving high-dose IV therapy.

Note: Final dosing decisions must be individualized by a qualified healthcare provider.

Safety Profile & Considerations

Common Side Effects

• Nausea (≈ 10 % of patients).
• Headache (≈ 8 %).
• Diarrhoea (≈ 5 %).
• Mild rash (≈ 3 %).
• Dizziness (≈ 2 %).

These events are usually transient and resolve without intervention.

Serious Adverse Events

Rarely, high plasma concentrations can precipitate central nervous system toxicity, manifesting as confusion, agitation, or seizures-reported in ≤ .1 % of patients receiving IV therapy with impaired renal function. Acute kidney injury may occur when acyclovir crystals precipitate in renal tubules, especially with concomitant nephrotoxic drugs; monitoring serum creatinine is advised.

Contra-indications

• Known hypersensitivity to acyclovir or valacyclovir.
• Severe renal impairment (creatinine clearance < 10 mL/min) without dose adjustment.

Pregnant women may use acyclovir when benefits outweigh potential risks; FDA classifies it as Category B, and extensive registries have not shown teratogenicity.

Drug Interactions

• Probenecid decreases renal clearance, raising acyclovir plasma levels by up to 50 %.
• Nephrotoxic agents (e.g., amphotericin B, NSAIDs) increase risk of renal dysfunction.
• Zidovudine co-administration may heighten-hance bone-marrow suppression.

CYP450 enzymes play a minimal role in acyclovir metabolism, limiting interaction potential with most other antivirals.

Special Populations

• Elderly: Reduced renal function often necessitates dose modification.
• Pediatrics: Dosing is weight-based; oral suspension is preferred for children under 12 kg.
• Hepatic impairment: No major dosage change required, as hepatic metabolism is negligible.
• Breastfeeding: Small quantities are excreted in milk; infant monitoring is recommended.

Overall, the safety profile remains favourable when prescribed according to renal function guidelines.

Frequently Asked Questions

• What is the difference between acyclovir and valacyclovir? Acyclovir requires activation by viral thymidine kinase, whereas valacyclovir is a pro-drug that converts to acyclovir after oral absorption, resulting in higher bioavailability (≈ 55 % vs 15-30 %). This allows less frequent dosing with valacyclovir.

• How long before acyclovir produces noticeable effects? Oral therapy usually begins to reduce viral shedding within 24 hours, and lesion crusting appears 2 days after the first dose. Topical cream shows improvement in lesion appearance by the second day of application.

• Is acyclovir safe for long-term use? Long-term suppressive therapy (≥ 12 months) has been studied in genital herpes, showing sustained efficacy without cumulative toxicity; renal function should be monitored annually (Acyclovir long-term safety, 2021).

• What should I do if I experience a rash while taking acyclovir? A mild rash is common and often self-limited; however, if the rash spreads, is accompanied by fever, or involves mucous membranes, seek medical attention promptly as this may indicate a hypersensitivity reaction.

• Can I take acyclovir with food? Food does not significantly alter oral absorption, so you may take the tablets with or without meals. Taking them with food may lessen gastrointestinal discomfort.

• How does acyclovir work against shingles? By inhibiting VZV DNA polymerase, acyclovir curtails viral replication in dorsal root ganglia, reducing the severity and duration of the painful rash associated with herpes zoster.

• Are there any concerns for kidney health? High doses, especially IV formulations, can precipitate renal crystals. Maintaining adequate hydration and adjusting the dose in renal impairment mitigates this risk.

• What information should I provide my doctor when discussing acyclovir? • Current health conditions (especially kidney disease). • All medications and supplements you are taking. • History of HSV or VZV infections and frequency of outbreaks. • Any known drug allergies, particularly to antiviral agents.

Disclaimer

The information provided about acyclovir is for general knowledge only. It does not replace professional medical consultation or the official prescribing information for medications containing this ingredient. All treatment decisions-including dosing, formulation selection, and monitoring-should be made under the supervision of a qualified healthcare provider who can assess individual medical history, current medications, and specific health needs. We assume all readers are responsible adults capable of making informed decisions about their health. Our online pharmacy offers access to medications containing acyclovir for individuals who may have limited availability through traditional pharmacies, prescription-based insurance schemes, or who are seeking affordable generic alternatives. Always consult your doctor before starting, changing, or discontinuing any medication containing acyclovir.

External Resources about Acyclovir

• CompoundingToday.com | Formulation: Acyclovir 43-mg/mL Oral Suspension, Preserved
• PRESCRIBING INFORMATION Acyclovir Capsules USP
• PRESCRIBING INFORMATION ZOVIRAX - Food and Drug …
• Aciclovir Pharmacology - Active Ingredient - RxReasoner
• Acyclovir Related Compound A USP Reference Standard Sigma-Aldrich