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Study of acetylsalicylic acid and diclofenac for treating blood clots in superficial venous malformations in children aged 6 to 17 years

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What is this trial about?

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

This study focuses on children experiencing thrombotic episodes, which are instances where blood clots form, within superficial venous malformations. A venous malformation is an abnormal buildup of blood vessels located close to the surface of the skin. The purpose of the study is to evaluate the effectiveness of acetylsalicylic acid compared to a placebo in managing the pain associated with these events. Participants in the study also use diclofenac, a type of non-steroidal anti-inflammatory drug, which is applied topically as a gel to the affected area.

The research follows a cross-over design, meaning that participants will receive different treatments at different times during the study. During the trial, some will receive the active medication, while others receive the placebo, in addition to the local gel. This process is conducted as a double-blind trial, which means neither the participants nor the researchers know which specific treatment is being administered at any given time. The treatment periods will last between 3 and 14 days.

The research process

The trial runs in 3 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial phase

    The participation begins with the use of diclofenac gel, which is a local non-steroidal anti-inflammatory drug used to manage pain. this gel is applied to the skin.

    One of two treatments will be administered for a period of 3 to 14 days. either the aspro 320 mg tablet (containing acetylsalicylic acid) will be taken orally at a total daily dose of 1920 mg, or a placebo (an inactive substance containing calcium hydrogen phosphate dihydrate) will be taken orally at a total daily dose of 1920 mg.

  2. Step 2

    Follow-up and monitoring

    Daily assessments of functional impairment are conducted using a visual analog scale, which is a tool to measure discomfort from 0 to 10.

    sleep quality is monitored once a day for 14 days using a specific measurement tool.

    The amount of pain medication consumed over 14 days is recorded to evaluate how well the treatment works.

    The impact on quality of life is measured using specific index tools at the start and after each medical event.

    Blood tests are performed to check coagulation markers, which are substances in the blood that help with clotting. these tests include a complete blood count (cbc), prothrombin time (pt), activated partial thromboplastin time (aptt), plasma fibrinogen, and d-dimers.

  3. Step 3

    Crossover period

    Because this is a cross-over trial, the treatments are switched. the group that previously received the aspro 320 mg will receive the placebo, and the group that previously received the placebo will receive the aspro 320 mg.

Who can join the trial?

10 criteria

  • The person must be between 6 and 17 years old.
  • The person must weigh at least 20 kilograms.
  • The person must have a superficial venous malformation, which is a cluster of abnormal, widened blood vessels located near the surface of the skin.
  • The condition must be confirmed by imaging, such as an MRI (a detailed picture using magnets), a CT scan (a detailed picture using X-rays), or a Doppler ultrasound (an imaging test that shows how blood flows through vessels).
  • The person must have phleboliths, which are small, hardened deposits of calcium found inside the blood vessels.
  • The person must have experienced superficial venous thrombosis, which means blood clots have formed in the small veins near the skin.
  • The person must have had at least 2 acute thrombotic episodes (sudden blood clot events) within the last 12 months.
  • A legal representative (such as a parent or guardian) must provide written permission for the child to join.
  • The person must be covered by a social security scheme (a government or private insurance system for healthcare costs).
  • Young women who are able to become pregnant must use a highly effective method of contraception (a way to prevent pregnancy, such as specific medicines or devices).

Who cannot join the trial?

21 criteria

  • You have deep venous malformations (abnormal growths of blood vessels located deep within the body) or syndromic venous malformations (blood vessel issues that are part of a larger medical syndrome).
  • You have G6PD deficiency (a condition where the body lacks enough of an enzyme that helps red blood cells work properly).
  • You have mastocytosis (a condition where too many certain types of white blood cells build up in the body).
  • You have a history of hemarthrosis (bleeding that occurs into a joint).
  • You are currently taking part in another medical research study.
  • You have a haemostasis pathology (a disorder that affects how your body stops bleeding), whether you were born with it or developed it later.
  • You are currently using treatments that affect how your blood clots, such as anticoagulants (blood thinners), platelet anti-aggregants (medicines that prevent blood cells from sticking together), or oral NSAIDs (medicines used to reduce pain and inflammation taken by mouth).
  • You experience frequent bleeding, such as epistaxis (nosebleeds) or other types of bleeding that require medical care.
  • You are taking mTOR inhibitors (a specific type of medicine used to treat certain blood vessel growths).
  • You have an active neoplasia (an abnormal growth of cells, such as a tumor) or an active infection that affects your blood's ability to clot.
  • You have a known allergy to acetylsalicylic acid (commonly known as aspirin).
  • You have galactose intolerance, Lapp lactase deficiency, or glucose or galactose malabsorption syndrome (conditions where the body cannot properly digest certain sugars).
  • You have a known allergy to NSAIDs (non-steroidal anti-inflammatory drugs used to treat pain and swelling).
  • You have Klippel-Trenaunay syndrome or Cloves syndrome (rare medical conditions that affect the growth of blood vessels and limbs).
  • You have a history of peptic ulcer disease (sores in the lining of the stomach or small intestine) or chronic gastritis (long-term inflammation of the stomach lining).
  • You have a history of asthma, angioedema (swelling under the skin), urticaria (hives), or acute rhinitis (sudden inflammation of the nose) triggered by certain pain medicines.
  • You are allergic to any of the excipients (inactive ingredients used to make a medicine) in the diclofenac gel.
  • You have damaged skin, such as dermatitis (skin inflammation), eczema, infected spots, burns, or wounds.
  • You are pregnant or breastfeeding.
  • You have severe renal insufficiency (serious kidney problems), severe hepatic insufficiency (serious liver problems), or severe uncontrolled cardiac insufficiency (serious heart problems).
  • You take methotrexate (a medicine used for various conditions) at a dose of 20 mg or more per week.
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Investigated drugs

  • Aspirin

    is a medication used in this study to help treat blood clots and reduce pain in children with certain vein issues.

  • Diclofenac

    is a gel applied to the skin to help reduce pain and swelling at the site of the problem.

What is already known about the treatment

  • Acetylsalicylic acid

    This medication is taken orally in the form of a tablet. It is a widely used and well-established medicine used to reduce pain, fever, and inflammation. It works by blocking specific enzymes in the body that produce chemicals responsible for pain and swelling. This drug belongs to a group of medicines known as non-steroidal anti-inflammatory drugs.

  • Calcium hydrogen phosphate dihydrate

    This substance is administered orally and is used in this study as a placebo, which means it has no active medicinal effect. It is a common, inactive ingredient often used as a filler in various oral medications. It is not used to treat any specific medical condition but serves to ensure the trial results are accurate.

  • Diclofenac diethylamine

    This medication is applied to the skin as a gel. It is a standard treatment used to relieve pain and swelling in joints or muscles. At a molecular level, it works by stopping the production of natural chemicals in the body that cause inflammation and pain. It is classified as a topical non-steroidal anti-inflammatory drug.

Investigated diseases

Thrombotic episodes in superficial venous malformations - This condition occurs when blood clots form within abnormal collections of veins located near the surface of the skin. These malformations are structural abnormalities in the blood vessels that are present from birth. When a clot develops in these vessels, it can lead to localized inflammation and discomfort. The progression involves the blockage of blood flow within the malformed veins. This process may cause the affected area to become swollen or tender.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2024-517595-38-00Protocol codeDR200091Estimated enrolment34 patientsSponsorCentre Hospitalier Regional Universitaire De Tours

sourced from the EU Clinical Trials Register and site verification

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