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How to Take Aciclovir Tablets for Cold Sores

Published on: June 03, 2026

Understanding how to take aciclovir tablets for cold sores correctly can significantly improve treatment outcomes and reduce outbreak duration. As a UK-registered pharmacy, we've guided thousands of patients through aciclovir treatment, and proper timing alongside correct dosing makes all the difference. This comprehensive guide covers everything you need to know about using aciclovir tablets effectively.

What Is Aciclovir and How Does It Work for Cold Sores?

Aciclovir is an antiviral medication licensed by the MHRA specifically to treat herpes simplex virus (HSV-1) infections, the primary cause of cold sores [1]. It works by interfering with viral DNA replication, preventing the virus from multiplying and spreading to healthy cells. Unlike topical treatments that work only on the skin surface, aciclovir tablets work systemically throughout your body.

Clinical studies demonstrate that aciclovir can reduce cold sore healing time by approximately 1-2 days when started early, and may reduce pain duration by a similar margin [1][2]. The medication is most effective when taken at the very first signs of a cold sore — that characteristic tingling or burning sensation many patients recognise before visible blisters appear.

In my experience as a pharmacist, patients who keep aciclovir tablets readily available and start treatment during the prodromal phase (those early warning signs) achieve significantly better outcomes than those who wait until blisters have fully formed.

Standard Aciclovir Dosage for Cold Sores: How to Take It

The standard aciclovir dosage for cold sores in adults is 200mg taken five times daily for five days [2]. This frequent dosing schedule is necessary because aciclovir has a relatively short half-life in the body, meaning blood levels drop quickly between doses. The five-times-daily regimen maintains therapeutic drug levels throughout the day.

Some prescribers may recommend an alternative regimen of 400mg taken three times daily for five days, which offers comparable efficacy with improved convenience [2]. This dosing schedule can improve adherence for patients who struggle with remembering five daily doses. Your UK prescriber will determine which regimen suits your circumstances during your clinical assessment.

Practical Dosing Schedule

For the 200mg five-times-daily regimen, space doses approximately 4 hours apart during waking hours. A typical schedule might be: 7am, 11am, 3pm, 7pm, and 11pm. You don't need to wake during the night for doses. For the 400mg three-times-daily option, take doses with breakfast, lunch, and dinner for easy adherence. Aciclovir can be taken with or without food, though taking it with meals may reduce potential stomach upset in sensitive individuals.

When to Start Aciclovir Treatment for Maximum Effectiveness

Timing is absolutely critical with aciclovir treatment. The medication works by preventing viral replication, so starting treatment before the virus has multiplied extensively produces the best results. Ideally, you should take your first dose within the first 24 hours of noticing symptoms — preferably within the first few hours [1][3].

The prodromal symptoms to watch for include tingling, itching, burning, or tenderness at the site where cold sores typically appear (usually around the lips or nose). Some patients describe a feeling of tightness or swelling. If you experience recurrent cold sores, you'll likely recognise these early warning signs. This is the optimal window to begin aciclovir tablets.

Research shows that aciclovir started after blisters have fully formed and crusted over provides minimal benefit [3]. At Cured Pharmacy, we recommend patients who experience frequent cold sores keep aciclovir tablets readily available at home, so treatment can begin immediately when symptoms start rather than waiting for a pharmacy visit.

Aciclovir Tablets vs Cream: Which Is More Effective?

Both aciclovir tablets and topical aciclovir cream (such as Numark Cold Sore Cream) are licensed treatments in the UK, but they work through different mechanisms and suit different situations. Aciclovir tablets work systemically, treating the infection from inside your body, while aciclovir cream works locally on the skin surface where applied.

Clinical evidence suggests oral aciclovir tablets may be more effective than topical cream for reducing healing time and symptom duration, particularly for severe or frequently recurring cold sores [2][4]. Tablets achieve higher drug concentrations at the site of infection and treat the virus throughout affected tissues, not just the surface. However, topical aciclovir cream offers the advantage of being available without prescription, making it accessible for immediate treatment.

In practice, some patients use both concurrently — tablets for systemic antiviral action and cream for additional local relief and protection of the affected area. Your UK prescriber can advise whether combination therapy might benefit your specific situation. At Cured Pharmacy, we stock both Aciclovir tablets (from £4.49, prescription required) and Numark Cold Sore Cream (from £4.49, no prescription needed).

Choosing the Right Formulation

Consider aciclovir tablets if you experience severe cold sores, frequent recurrences (more than 6 outbreaks yearly), cold sores in multiple locations, or immunocompromised status. Topical cream may suffice for mild, infrequent cold sores caught very early. Patients with difficulty swallowing tablets or those seeking immediate treatment without prescription assessment may prefer starting with cream. Your clinical assessment will determine the most appropriate option.

What to Expect During Aciclovir Treatment

Most patients tolerate aciclovir tablets very well, with side effects being uncommon and generally mild. The most frequently reported side effects include headache, nausea, and dizziness, though these affect fewer than 10% of patients [1]. Drinking plenty of water throughout your treatment course (aim for 2-3 litres daily) helps maintain kidney function and may reduce headache risk.

You should notice improvement in symptoms within 2-3 days of starting treatment, though complete healing typically takes 4-7 days total [2]. The cold sore may still progress through its normal stages (tingling, blistering, weeping, crusting, healing), but each stage should be shorter and less severe than without treatment. Pain and discomfort often improve before visible healing occurs.

Complete your full five-day course even if symptoms improve earlier. Stopping aciclovir prematurely may allow the virus to rebound, potentially prolonging your outbreak. If symptoms worsen or haven't improved after 5 days of treatment, contact your prescriber or GP for reassessment, as you may require extended treatment or investigation for other causes.

Preventing Cold Sore Recurrence and Suppressive Therapy

For patients experiencing frequent cold sore outbreaks (typically defined as 6 or more per year), suppressive aciclovir therapy may be appropriate. This involves taking aciclovir continuously at a lower daily dose (usually 400mg twice daily) to prevent outbreaks rather than treating them as they occur [3][4]. Clinical studies show suppressive therapy can reduce recurrence frequency by 70-80% in suitable patients.

Suppressive therapy requires ongoing prescription and monitoring by a UK prescriber, as it involves long-term medication use. Your prescriber will assess whether the frequency and severity of your outbreaks justify continuous treatment versus episodic treatment of individual outbreaks. Factors considered include outbreak frequency, impact on quality of life, and any underlying immune conditions.

Beyond medication, certain lifestyle measures may help reduce cold sore frequency. Common triggers include UV exposure (use SPF lip balm), stress, illness, fatigue, and hormonal changes. While aciclovir treats and prevents outbreaks effectively, identifying and managing your personal triggers provides additional protection. Our clinical team at Cured Pharmacy can discuss both pharmaceutical and lifestyle approaches during your consultation.

Who Should Consider Suppressive Therapy

Suppressive aciclovir therapy may benefit patients with 6+ outbreaks yearly, cold sores that significantly impact work or social life, outbreaks triggered by predictable events (such as sun exposure or stress), or immunocompromised status. It's also sometimes prescribed short-term before major events like weddings. Your UK prescriber will determine eligibility based on your medical history and outbreak pattern during your clinical assessment.

Scientific References

1. Spruance, S. L., et al. (2003). Peroral famciclovir in the treatment of experimental ultraviolet radiation-induced herpes simplex labialis: a double-blind, dose-ranging, placebo-controlled, multicenter trial. Journal of Infectious Diseases, 187(10), 1500-1507. https://doi.org/10.1086/374877 [accessed 13 August 2026]
2. Spruance, S. L., et al. (1997). Acyclovir cream for treatment of herpes simplex labialis: results of two randomized, double-blind, vehicle-controlled, multicenter clinical trials. Antimicrobial Agents and Chemotherapy, 41(7), 1437-1443. https://doi.org/10.1128/AAC.41.7.1437 [accessed 13 August 2026]
3. Rooney, J. F., et al. (1993). Oral acyclovir to suppress frequently recurring herpes labialis. A double-blind, placebo-controlled trial. Annals of Internal Medicine, 118(4), 268-272. https://doi.org/10.7326/0003-4819-118-4-199302150-00004 [accessed 13 August 2026]
4. Chi, C. C., et al. (2015). Interventions for prevention of herpes simplex labialis (cold sores on the lips). Cochrane Database of Systematic Reviews, 2015(8), CD010095. https://doi.org/10.1002/14651858.CD010095.pub2 [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.