Skip to content
Clinical Trials – home

Rare diseases

Investigational molecules

Locations

Our offerNewsroom

Recruiting

Study comparing aciclovir gel and cream effectiveness in treating recurrent cold sores (herpes labialis)

Verified siteRegistered drug
Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

What is this trial about?

A plain-language summary of the goals, design and what participants do

This study examines treatments for Recurrent Herpes Labialis, commonly known as cold sores - a condition that causes recurring outbreaks of blisters and sores around the lips. The study compares two medications containing the antiviral substance aciclovir: Lipovir gel and Zovirax cream, along with a placebo.

The purpose is to determine if Lipovir gel works as effectively as Zovirax cream in treating cold sores. Both medications contain the same amount of active ingredient (5% aciclovir) but come in different forms - one as a gel and the other as a cream. The medications are applied directly to the skin where cold sores appear.

During the study, participants who experience a cold sore outbreak will apply their assigned treatment to the affected area. They will use the medication for up to 10 days and keep track of how their cold sore heals. The main focus will be on how long it takes for the cold sore to heal completely, from the time treatment begins until the skin returns to normal or symptoms stop.

The research process

The trial runs in 4 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial evaluation

    Your participation begins when you experience early signs (called prodromal symptoms) of a cold sore outbreak, such as itching, redness, burning, tingling, or irritation in the lip area.

    You will be randomly assigned to receive one of three treatments: Lipovir Gel, Zovirax Cream, or a placebo (inactive treatment).

    All treatments contain 5% aciclovir, except for the placebo

  2. Step 2

    Treatment application

    You will need to apply the assigned treatment to the affected area on your lips when you notice the first signs of a cold sore outbreak

    The medication should be applied directly to the skin of the affected area

    You will receive specific instructions on how often to apply the treatment and for how long to continue using it

  3. Step 3

    Daily monitoring

    You will need to keep a daily record in a study diary

    Record any changes in your symptoms and cold sore appearance

    Note any side effects or skin reactions you may experience

    Document the time when the cold sore completely heals (when the scab falls off and only light redness may remain)

  4. Step 4

    Assessment of results

    A healthcare provider will evaluate how long it takes for your cold sore to heal completely

    You will be asked to rate how well you tolerated the treatment

    You will provide feedback on how acceptable the treatment was to use

    Any side effects that occurred during the treatment period will be documented

Who can join the trial?

12 criteria

  • Must have experienced at least 3 episodes of cold sores (herpes labialis) in the past year
  • At least half of these cold sore outbreaks must be preceded by early warning signs (prodromal symptoms) such as:
    • Itching
    • Redness
    • Burning
    • Tingling
    • Sense of irritation
    • At least half of these early warning signs must lead to typical cold sore symptoms such as:
      • Ulcers
      • Fluid-filled blisters
      • Hard crusts
      • Must be 18 years or older when signing the consent form
      • Must be able to read, understand, and sign the informed consent document
      • Must be able to understand and follow study procedures, including completing a daily diary

Who cannot join the trial?

12 criteria

  • History of allergic reactions to acyclovir (active ingredient in Zovirax) or similar medications
  • Pregnancy or breastfeeding
  • Current participation in other clinical trials
  • Use of antiviral medications in the past 14 days
  • Presence of other skin conditions in the area affected by cold sores
  • Weakened immune system due to medications or medical conditions
  • History of severe or frequent herpes outbreaks requiring constant medication
  • Any serious medical condition that could interfere with study participation
  • Unable to follow study procedures or attend follow-up visits
  • Known sensitivity to any ingredients in the study medications
  • Active cold sore that has been present for more than 48 hours
  • Use of topical treatments on the affected area in the past 24 hours
Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

Tell us about your condition – we search every trial in Europe and connect you with the right site.

We usually reply within a few days

Verified sites

All sites with verified contact details – recruitment status may not be available; ask directly

Trial locations

Where you can join this trial

Countries are shaded by recruitment status. Click a recruiting country to ask about joining there.

Recruiting
Not finding your country?

Not sure what to do next?

Joining a clinical trial can seem overwhelming. We guide you step by step, so you know exactly what to expect and how we support you through the process.

See the full process and FAQ

Investigated drugs

Lipovir Gel (containing acyclovir) is a topical medication used to treat cold sores caused by herpes labialis. It works by stopping the growth of the herpes virus, helping to reduce the duration and severity of cold sore outbreaks. Zovirax Cream (containing acyclovir) is a well-established topical antiviral medication used to treat cold sores. It helps speed up healing and reduces the symptoms of herpes labialis outbreaks by preventing the virus from multiplying. Both medications contain the same active ingredient (acyclovir) but are manufactured by different companies and have different formulations - one as a gel and one as a cream.

What is already known about the treatment

  • Lipovir Gel

    A topical antiviral medication containing 5% acyclovir, administered as a gel formulation for the treatment of recurrent herpes labialis (cold sores). This medication works by interfering with viral DNA synthesis, effectively stopping the herpes simplex virus from multiplying in infected cells. It belongs to the class of antiviral medications and is applied directly to the affected area at the first sign of a cold sore outbreak.

  • Zovirax Cream

    A topical antiviral preparation containing 5% acyclovir, formulated as a cream for treating recurrent herpes labialis (cold sores). The medication penetrates the skin to reach infected cells, where it blocks viral DNA replication and prevents the herpes simplex virus from spreading to healthy cells. As a well-established treatment in medical practice, this prescription medication is applied topically to the affected area and belongs to the nucleoside analog antiviral drug class.

Investigated diseases

Recurrent Herpes Labialis - A common viral infection that causes cold sores or fever blisters, primarily on or around the lips. The condition is caused by the herpes simplex virus type 1 (HSV-1) and is characterized by recurring episodes of fluid-filled blisters. The infection typically begins with tingling or burning sensation, followed by the formation of small blisters that eventually break, form a crust, and heal. Episodes can be triggered by factors such as stress, sunlight exposure, fever, or hormonal changes. The virus remains dormant in nerve cells between outbreaks and can reactivate periodically.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2023-510338-10-00Protocol codeOP-LIPC02Estimated enrolment200 patientsSponsorLaboratorios Ojer Pharma S.L.

sourced from the EU Clinical Trials Register and site verification

Want to learn more about this trial or check if you can participate?

Clinical Trials Concierge

Prefer not to search? Our Concierge searches the trials for you.

Tell us about your condition – we search every trial in Europe and connect you with the right site.