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A Study of Candesartan to Prevent Chronic Cluster Headache Attacks in Adults with Chronic Cluster Headache

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What is this trial about?

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

This study is looking at chronic cluster headache, a condition where people experience severe headaches that occur in patterns or clusters over time. The treatment being tested is candesartan, a medication that is normally used to treat high blood pressure but is being studied here to see if it can help prevent cluster headache attacks. Participants will receive either candesartan at a dose of 32 milligrams or placebo during different phases of the study. The purpose of the study is to see if candesartan can reduce how often severe and very severe cluster headache attacks happen compared to placebo.

The study is designed as a crossover trial, which means that participants will receive both the active medication and placebo at different times, with periods in between where no study medication is given to wash out the previous treatment. The study begins with a two-week period where participants keep track of their headache attacks in a diary before starting any treatment. Then participants will go through two four-week treatment periods where they take either candesartan or placebo, with the order being randomly assigned. Between these treatment periods there is a wash-out phase. After completing these phases, there is an optional open treatment period where participants may continue with candesartan.

Throughout the study, participants will record their headache attacks, including how severe they are and how often they occur. The study will measure changes in the number of severe and very severe attacks per week, how many people experience at least a 50 percent reduction in attacks, and changes in headache intensity. Other measurements include how much rescue medication participants need to use, improvements in quality of life and disability related to cluster headaches, and overall impression of improvement. The study will also monitor for any side effects and changes in mood or suicidal thoughts using specific questionnaires.

The research process

The trial runs in 8 steps – from screening to follow-up. Each step says what happens and what the team monitors.

  1. Step 1

    Baseline period

    This initial phase lasts two weeks.

    During this period, you will keep a diary to record your headache attacks.

    You must experience between 4 attacks per week and a maximum of 8 attacks per day of severe or very severe intensity on average.

    This information will be used to compare with later phases of the study.

  2. Step 2

    First blinded treatment period

    This phase lasts four weeks.

    You will receive either candesartan 32 mg or placebo (an inactive substance) taken by mouth.

    Neither you nor your doctor will know which treatment you are receiving during this period.

    Candesartan is a medication that affects blood vessels and may help prevent cluster headache attacks.

    You will continue to record your headache attacks in a diary, including their frequency and intensity.

    You will also record any acute treatments you use, such as inhaled oxygen.

  3. Step 3

    First wash-out period

    After the first treatment period, there will be a wash-out phase.

    During this time, the medication from the previous period will clear from your body.

    The duration of this phase is determined by the study protocol.

  4. Step 4

    Second blinded treatment period

    This phase also lasts four weeks.

    You will receive the opposite treatment from the first period. If you received candesartan 32 mg before, you will now receive placebo, or vice versa.

    The treatment is taken by mouth.

    Neither you nor your doctor will know which treatment you are receiving.

    You will continue to keep a diary of your headache attacks, their frequency, intensity, and any acute treatments used.

  5. Step 5

    Second wash-out period

    After the second treatment period, there will be another wash-out phase.

    This allows the medication to clear from your body before the next phase.

  6. Step 6

    Open-label treatment period

    This phase lasts eight weeks.

    During this period, you will receive candesartan, and both you and your doctor will know what treatment you are receiving.

    The medication is taken by mouth.

    You will continue to record your headache attacks and any acute treatments used.

    If you were free of severe or very severe attacks at the end of the second blinded period, the study will monitor how long it takes for attacks to return.

    The study will also track whether you reduce your use of acute treatments by at least 50% compared to the baseline period.

  7. Step 7

    Final wash-out period

    After the open-label treatment period, there will be a final wash-out phase.

    If you were taking candesartan during the open-label period, the study will monitor how long it takes for severe or very severe attacks to return after stopping the medication.

  8. Step 8

    Assessment throughout the study

    At specific time points (weeks 4, 12, and 20 after baseline), you will complete questionnaires to assess your overall improvement and how cluster headache affects your daily life.

    These questionnaires include the Patient Global Impression of Improvement, which asks you to rate how much better or worse you feel.

    You will also complete the Hospital Anxiety and Depression Scale to assess changes in mood.

    The Cluster Headache Impact Questionnaire will measure how cluster headache affects your ability to function.

    At baseline, you will complete the Columbia Suicide Severity Rating Scale, which assesses thoughts or behaviors related to suicide.

    At week 8 of the open-label period, you will rate your overall condition compared to the end of the second blinded treatment period.

Who can join the trial?

9 criteria

  • You must be between 18 and 70 years old at the time you sign the consent form to join the study
  • You must have chronic cluster headache, which is a condition where severe headaches occur in patterns or clusters without long pain-free periods between them, and this must be confirmed according to specific medical guidelines at the time you join
  • You must have had chronic cluster headache for more than 1 year, and your usual headache periods should last more than 5 weeks
  • If you have other types of headaches that happen occasionally, such as migraine (intense headaches often with nausea and light sensitivity) or tension-type headache (headaches that feel like pressure or tightness), you must be able to clearly tell the difference between these and your cluster headache attacks based on how the pain feels and other symptoms that come with it
  • During a two-week observation period before treatment starts, you must experience between 4 attacks per week and a maximum of 8 attacks per day that are severe or very severe in intensity on average
  • Your cluster headache symptoms at the time you join the study and during the observation period must be typical of what you usually experience
  • If you are a woman who can become pregnant, you must not be pregnant or planning to become pregnant during the study, and you must use an approved birth control method throughout the study period
  • If you are a man, no specific birth control requirements are needed
  • You must be able to understand and sign the consent form, and you must be willing and able to follow all the requirements and rules of the study

Who cannot join the trial?

1 criterion

  • No exclusion criteria have been provided in the study information available
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Investigated drugs

  • Candesartan

    is a medication that belongs to a group of medicines called angiotensin-receptor antagonists. In this study, it is being tested to see if it can help prevent cluster headache attacks in people who suffer from chronic cluster headaches. The goal is to find out if this medication can reduce how often severe and very severe headache attacks occur.

  • Placebo

    is an inactive treatment that looks like the real medication but contains no active medicine. It is used in this study to compare against candesartan to help determine if candesartan actually works better than no treatment at all.

What is already known about the treatment

Candesartan – Candesartan is a medication that belongs to a group of drugs called angiotensin-receptor blockers, which are commonly used to treat high blood pressure by relaxing blood vessels. In this clinical trial, it is being studied as a preventive treatment for chronic cluster headache, a severe type of recurring headache that occurs in cyclical patterns. The medication works at the molecular level by blocking specific receptors that normally respond to a hormone called angiotensin II, which causes blood vessels to narrow; by blocking these receptors, candesartan helps blood vessels stay relaxed and may reduce the frequency of severe headache attacks. The drug is typically taken by mouth in tablet form, and in this study, participants receive a 32 mg dose to evaluate its effectiveness in preventing cluster headaches.

Investigated diseases

Chronic Cluster Headache – Chronic cluster headache is a severe type of headache disorder characterized by recurring intense pain attacks that occur in patterns or clusters. The attacks typically affect one side of the head and are often centered around the eye area. Unlike episodic cluster headaches that come in periods followed by remission, chronic cluster headache occurs without significant pain-free periods, with attacks continuing for more than one year without remission or with remission periods lasting less than three months. Individual attacks can last from 15 minutes to several hours and may occur multiple times throughout the day. The condition causes severe, sharp, or stabbing pain that can be accompanied by symptoms such as eye redness, tearing, nasal congestion, or eyelid swelling on the affected side. The frequency and intensity of attacks can significantly impact daily activities and quality of life.
Trial detailsLast updated 2 Oct 2026
Age18+ yearsPhasePhase IIITrial ID2025-521529-34-00Protocol codeChronic CandClus2 V1Estimated enrolment44 patientsSponsorHelse Bergen HF

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