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BNF Aciclovir Strength Comparison Guide

Published on: June 03, 2026

Understanding the aciclovir strength comparison UK options is essential for effective cold sore management. At Cured Pharmacy, we dispense both topical aciclovir 5% cream from £4.49 and prescription-strength oral tablets, helping you choose the right formulation based on your clinical needs and symptom severity.

Aciclovir Strength Comparison UK: Cream vs Tablets

Aciclovir is available in the UK in two primary formulations: topical 5% cream for mild cold sores and oral tablets (200mg or 400mg) for more severe or recurrent infections [1]. The British National Formulary (BNF) recommends topical treatment for early-stage cold sores, whilst oral aciclovir may be prescribed for immunocompromised patients or those experiencing frequent recurrences [2].

Topical aciclovir 5% cream delivers the active ingredient directly to the affected area, achieving high local concentrations without significant systemic absorption. Clinical trials demonstrate that when applied at the first tingling sensation (prodrome), topical aciclovir can reduce healing time by approximately 0.5 to 1 day compared to placebo [1]. Oral tablets work systemically, providing broader antiviral coverage and are typically reserved for more severe presentations or prophylactic use in patients with frequent outbreaks exceeding six episodes per year [2].

How Aciclovir 5% Cream Works for Cold Sores

Aciclovir 5% cream contains 50mg of aciclovir per gram, making it the standard over-the-counter strength licensed by the MHRA for herpes simplex labialis (cold sores) [1]. The medication works by inhibiting viral DNA polymerase, preventing the herpes simplex virus type 1 (HSV-1) from replicating within infected cells.

For optimal efficacy, the BNF recommends applying aciclovir cream five times daily for five days, starting at the earliest sign of a cold sore outbreak [2]. The cream should be applied to the affected area and approximately 1cm of surrounding skin. Clinical evidence shows that early application — ideally during the prodromal tingling phase — produces the best outcomes, with some patients experiencing reduced blister formation when treatment begins within the first few hours of symptom onset [1].

When to Choose Topical Aciclovir

Topical aciclovir 5% cream is appropriate for immunocompetent adults experiencing occasional cold sores (fewer than six episodes annually). It's available without prescription at UK pharmacies, though a brief consultation ensures suitability and excludes contraindications such as hypersensitivity to aciclovir or valaciclovir. Patients who experience only mild, infrequent outbreaks typically achieve satisfactory results with topical treatment alone.

Oral Aciclovir Tablets: 200mg and 400mg Dosing

Oral aciclovir tablets are prescription-only medicines in the UK, available in 200mg, 400mg, and 800mg strengths. For cold sore treatment, the BNF recommends either 200mg five times daily for five days or 400mg three times daily for five days [2]. Both regimens provide equivalent systemic exposure and clinical efficacy, with the 400mg dosing schedule offering improved convenience for patients who struggle with frequent dosing.

Oral aciclovir is typically prescribed for patients with severe cold sores, those who are immunocompromised, or individuals experiencing frequent recurrences that significantly impact quality of life [2]. In clinical trials, oral aciclovir initiated within 48 hours of symptom onset reduced healing time by an average of 1 to 2 days and decreased the duration of viral shedding, potentially reducing transmission risk [3]. Suppressive therapy with 400mg twice daily may be considered for patients with six or more recurrences per year, subject to prescriber assessment.

Aciclovir 400mg vs 200mg: Which Dose Is Right?

The choice between 200mg and 400mg aciclovir depends on dosing frequency preference rather than efficacy differences. The 200mg dose requires five administrations daily (approximately every four hours during waking hours), whilst the 400mg dose simplifies the regimen to three times daily [2]. Your UK prescriber will consider your lifestyle, adherence patterns, and clinical presentation when recommending a specific strength. Both doses are equally effective when taken as prescribed, and neither formulation has demonstrated superior outcomes in head-to-head trials for immunocompetent patients [3].

Aciclovir 5% Cream vs Tablets: Efficacy and Suitability

Direct comparative trials between topical and oral aciclovir for cold sores in immunocompetent adults show modest differences in healing time reduction. Topical aciclovir 5% cream typically shortens healing by 0.5 to 1 day, whilst oral aciclovir may reduce healing time by 1 to 2 days when initiated early [1][3]. However, the clinical significance of this difference is debated, and many patients achieve satisfactory outcomes with topical treatment alone.

The decision between formulations should consider outbreak frequency, severity, and patient preference. Topical treatment offers the advantage of minimal systemic side effects and no prescription requirement, making it accessible for immediate use. Oral aciclovir provides systemic antiviral activity and is preferred for patients with frequent recurrences, immunosuppression, or cold sores affecting large areas. At Cured Pharmacy, our UK-registered clinical team assesses your individual circumstances during a free online consultation to recommend the most appropriate aciclovir strength and formulation.

Side Effects and Safety Considerations by Strength

Topical aciclovir 5% cream is generally well-tolerated, with the most common side effects being mild stinging, burning, or dryness at the application site [1]. Systemic absorption from topical application is minimal, making it suitable for most patients, including pregnant and breastfeeding women after consultation with a healthcare professional.

Oral aciclovir tablets may cause systemic side effects, though these are typically mild and transient. The most frequently reported adverse effects include headache, nausea, and gastrointestinal discomfort [2]. Adequate hydration is recommended during oral aciclovir therapy to reduce the risk of crystalluria, particularly in patients receiving higher doses. Renal impairment requires dose adjustment, and your prescriber will review your medical history to ensure safe prescribing. Serious side effects are rare but may include hypersensitivity reactions or neurological symptoms in patients with compromised renal function [3].

Drug Interactions and Contraindications

Aciclovir has few clinically significant drug interactions, though caution is advised when combining oral aciclovir with nephrotoxic medications such as aminoglycosides or high-dose NSAIDs [2]. Probenecid may increase aciclovir plasma concentrations by reducing renal clearance. Aciclovir is contraindicated in patients with known hypersensitivity to aciclovir, valaciclovir, or any excipients. Your UK prescriber will review your current medications and medical history during the online consultation to identify any potential interactions or contraindications before prescribing.

Buying Aciclovir Online UK: What to Expect

At Cured Pharmacy, we supply genuine UK-licensed aciclovir products with transparent upfront pricing. Our Numark Cold Sore Cream containing aciclovir 5% is available from £4.49, providing immediate access to over-the-counter cold sore treatment. For patients requiring prescription-strength oral aciclovir tablets, we offer a free online consultation completed in under three minutes, with assessment by our UK-registered clinical team led by Superintendent Pharmacist Tarun Kumar (GPhC 2233073).

All prescription aciclovir orders require clinical assessment to ensure suitability, appropriate dosing, and safe use. Our consultation process reviews your medical history, current medications, outbreak frequency, and symptom severity. Once approved by a UK prescriber, your medication is dispensed by our GPhC-registered pharmacy (9012511) and delivered in 100% discreet packaging. We guarantee the lowest prices in the UK and supply only genuine, MHRA-licensed medicines sourced from reputable UK wholesalers.

Next Steps: Starting Aciclovir Treatment

If you're experiencing cold sores and considering aciclovir treatment, start by assessing your outbreak frequency and severity. For occasional, mild cold sores, topical aciclovir 5% cream available without prescription may be sufficient. If you experience frequent recurrences, severe outbreaks, or have underlying immunosuppression, speak with a UK prescriber about oral aciclovir tablets. Our clinical team is available to answer questions and guide you toward the most appropriate treatment option based on current BNF guidance and your individual circumstances.

Scientific References

1. Spruance, S. L., et al. (2002). Acyclovir cream for treatment of herpes simplex labialis: results of two randomized, double-blind, vehicle-controlled, multicenter clinical trials. Antimicrobial Agents and Chemotherapy, 46(7), 2238–2243. https://doi.org/10.1128/AAC.46.7.2238-2243.2002 [accessed 13 August 2026]
2. Joint Formulary Committee. (2024). British National Formulary (BNF) 87. London: BMJ Group and Pharmaceutical Press. Retrieved from https://bnf.nice.org.uk/ [accessed 13 August 2026]
3. Raborn, G. W., et al. (1997). Oral acyclovir and herpes labialis: a randomized, double-blind, placebo-controlled study. Journal of the American Dental Association, 128(9), 1281–1286. https://doi.org/10.14219/jada.archive.1997.0414 [accessed 13 August 2026]

Information on this page is for educational purposes only and is not medical advice. All prescription treatments require clinical assessment by a UK-registered prescriber. Always consult a qualified healthcare professional before starting any new medication.