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Study on Oxybutynin and Venlafaxine for Reducing Hot Flashes in Women Undergoing Endocrine Therapy After Breast Cancer

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What is this trial about?

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

The RED FLASH study is focused on helping women who have had breast cancer and are experiencing hot flashes as a side effect of their ongoing treatment. Hot flashes are sudden feelings of warmth, often intense, that can occur in women undergoing endocrine therapy after breast cancer. This study is comparing two treatments: oxybutynin and venlafaxine. Oxybutynin is usually used to treat bladder issues, while venlafaxine is commonly used as an antidepressant. Both medications are being tested to see how well they can reduce the number and severity of hot flashes.

The purpose of the study is to find out which of these two medications is more effective in reducing hot flashes. Participants will receive both treatments at different times during the study, allowing researchers to compare the effects within the same individual. This approach is known as a "cross-over" study. The study will last for several weeks, during which participants will take one medication for a period, then switch to the other. Throughout the study, participants will keep a daily record of their hot flashes in a Hot Flash Diary.

In addition to tracking hot flashes, the study will also look at other factors such as any side effects, sleep quality, overall quality of life, and mental health aspects like anxiety and depression. The study aims to provide valuable information that could help improve the quality of life for women dealing with hot flashes after breast cancer treatment.

The research process

The trial runs in 7 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Initial assessment

    Upon joining the study, an initial assessment is conducted to confirm eligibility. This includes verifying that you are a pre-, peri-, or postmenopausal woman aged 18 or above, currently undergoing endocrine therapy with tamoxifen, aromatase inhibitors, or luteinizing hormone-releasing hormone analogues for at least 4 weeks, and experiencing at least 14 hot flashes per week for a minimum of 1 month.

  2. Step 2

    Randomization and treatment assignment

    You will be randomly assigned to receive either oxybutynin or venlafaxine to manage hot flashes. Oxybutynin is taken orally, while venlafaxine is also administered orally.

  3. Step 3

    Treatment phase

    The treatment phase lasts for 6 weeks. During this time, you will take the assigned medication as directed. The specific dosage and frequency will be provided by the study team.

  4. Step 4

    Daily hot flash diary

    Throughout the 6-week treatment phase, you will be required to maintain a daily diary to record the number and severity of hot flashes. This information is crucial for assessing the effectiveness of the treatment.

  5. Step 5

    Evaluation of primary and secondary endpoints

    The primary endpoint is the number and severity of hot flashes, which will be evaluated using the data from your hot flash diary. Secondary endpoints include monitoring for any adverse events, assessing sleep quality, quality of life, health status, anxiety and depression, cognitive function, sexual function, personal preference, and adherence to the treatment.

  6. Step 6

    Cross-over phase

    After the initial 6-week treatment phase, you may switch to the alternative medication (from oxybutynin to venlafaxine or vice versa) for another 6-week period, following the same procedures as the initial phase.

  7. Step 7

    Final assessment

    At the end of the study, a final assessment will be conducted to evaluate the overall effectiveness of the treatments and gather your feedback on personal preference and adherence.

Who can join the trial?

3 criteria

  • Women who are either before menopause, going through menopause, or have completed menopause and are 18 years or older.
  • Women who need to take **endocrine therapy** (a treatment that blocks or removes hormones) and have already started taking medications like tamoxifen, aromatase inhibitors, or luteinizing hormone-releasing hormone analogues for at least 4 weeks. They should plan to continue these medications during the study.
  • Women who experience **hot flashes** (sudden feelings of warmth, often over the face, neck, and chest) at least 14 times a week for at least 1 month and want to start taking medication to help with this.

Who cannot join the trial?

3 criteria

  • Participants must not have any other type of cancer besides breast cancer.
  • Participants should not be male, as the study is only for females.
  • Participants must not be part of a vulnerable population, which means they should not be in a situation where they are unable to make decisions for themselves.
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Investigated drugs

  • Oxybutynin

    is a medication commonly used to treat symptoms of overactive bladder, such as frequent or urgent urination. In this trial, it is being tested for its ability to reduce hot flashes in women who are undergoing endocrine therapy after breast cancer treatment. The goal is to see if it can help manage these uncomfortable symptoms.

  • Venlafaxine

    is an antidepressant that belongs to a class of medications known as serotonin-norepinephrine reuptake inhibitors (SNRIs). It is often used to treat depression and anxiety disorders. In this study, venlafaxine is being evaluated for its effectiveness in reducing hot flashes in women receiving endocrine therapy after breast cancer. The trial aims to determine if venlafaxine can provide relief from these symptoms.

What is already known about the treatment

  • Oxybutynin

    Oxybutynin is typically administered orally in tablet form. It is currently being studied for its effectiveness in reducing hot flashes in women undergoing endocrine therapy after breast cancer. The medication is primarily used to treat symptoms of overactive bladder, but in this context, it is being evaluated for its potential to alleviate hot flashes. Oxybutynin works by blocking certain receptors in the body, which helps to relax bladder muscles and may also influence temperature regulation. It is classified as an anticholinergic agent.

  • Venlafaxine

    Venlafaxine is usually taken orally in the form of tablets or extended-release capsules. It is being investigated for its ability to reduce hot flashes in women receiving endocrine therapy following breast cancer treatment. Venlafaxine is commonly used as an antidepressant, but it is also known to help manage hot flashes. It functions by increasing the levels of serotonin and norepinephrine in the brain, which can help stabilize mood and potentially reduce the frequency and severity of hot flashes. It belongs to the class of medications known as serotonin-norepinephrine reuptake inhibitors (SNRIs).

Investigated diseases

Breast Cancer – Breast cancer is a disease where cells in the breast grow uncontrollably, forming a tumor that can often be felt as a lump. It typically begins in the ducts or lobules of the breast and can spread to other parts of the body if not managed. The progression of breast cancer can vary, with some tumors growing slowly and others more rapidly. Hormonal, genetic, and environmental factors can influence its development. Symptoms may include changes in breast shape, skin dimpling, or nipple discharge. Early detection through screening can help manage the disease more effectively.
Trial detailsLast updated 7 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2023-507847-13-00Estimated enrolment67 patientsSponsorReinier de Graaf Groep

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