A Study of Candesartan Compared to Placebo in Adults with Episodic Cluster Headache to Prevent Severe Headache Attacks

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What is this study about?

This study is looking at episodic cluster headache, a condition where people experience severe headache attacks that occur in patterns or cycles called bouts. 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 tablets or placebo, and both will be given in capsules so that no one knows which treatment they are receiving. The purpose of the study is to find out if candesartan can reduce the number of severe and very severe cluster headache attacks compared to placebo during a three-week treatment period.

The study involves several phases that participants will go through over time. First, there is a one-week period before treatment starts where participants keep a diary of their headache attacks to establish a starting point. Then comes a three-week blinded phase where participants take either candesartan up to 32 milligrams daily or placebo, with neither the participants nor the doctors knowing which treatment is being given. During this time, participants continue to record their headache attacks, how severe they are, and what medications they use to treat them. After the three-week blinded phase, there is an optional treatment period where participants may continue taking the study medication, followed by a wash-out phase where the medication is stopped to see what happens.

Throughout the study, participants will be asked to complete questionnaires about how much their condition has improved, how the headaches affect their daily life, and how they are feeling emotionally. The study will track how often severe and very severe attacks occur, how intense the attacks are, and how much rescue medication participants need to use. Researchers will also monitor how long it takes for attacks to stop completely and whether attacks return after treatment ends. The study is designed to gather information about whether candesartan can effectively prevent cluster headache attacks and improve the quality of life for people living with this condition.

1 Baseline diary period

This period lasts one week before receiving any treatment.

During this time, you will record all your headache attacks in a diary.

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 your headache frequency during the treatment period.

2 Blinded treatment phase

This phase lasts three weeks.

You will be randomly assigned to receive either candesartan 32 mg or placebo (an inactive substance that looks like the real medication).

Candesartan is a medication that blocks certain receptors in the body and may help reduce the frequency of severe headache attacks.

The medication is taken by mouth in the form of encapsulated tablets.

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

You will continue to record all your headache attacks, their intensity, and any medications you use to treat them.

3 Open treatment phase

This phase follows the blinded treatment phase.

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

The duration of this phase will be specified by your study doctor.

You will continue to monitor and record your headache attacks and any treatments you use.

If you were free from attacks at the end of the blinded phase, the study will track when or if your severe attacks return.

4 Wash-out phase

This phase occurs after the open treatment phase if you were taking candesartan during that period.

You will stop taking the study medication.

The purpose is to observe if and when your severe headache attacks return after stopping the medication.

You will continue to record any headache attacks during this time.

5 Assessment visits

Throughout the study, you will complete questionnaires at specific time points: at week 3, week 9, and week 14 after the baseline period.

These questionnaires will ask about your overall improvement, how your headaches affect your daily life, and your mood.

You will rate how much better you feel compared to before starting the treatment.

Questions about your emotional well-being, including anxiety and depression symptoms, will be included.

You will also be assessed for any thoughts related to self-harm using a specific questionnaire.

At week 8 of the open treatment phase, you will rate your overall condition compared to the end of the blinded treatment phase.

Who Can Join the Study?

You must be between 18 and 70 years old when you sign the consent form to join the study
You must have episodic cluster headache, which is a type of severe headache that occurs in patterns or cycles, with pain-free periods in between
You must have had at least one previous period of cluster headache that lasted more than 5 weeks
If you have other types of headaches such as migraine (a headache disorder causing severe throbbing pain) or tension-type headache (a headache causing mild to moderate pressing or tightening pain), you must be able to clearly tell them apart from your cluster headache attacks based on how the pain feels and other symptoms you experience
During the one-week observation period before treatment starts, you must have between 4 attacks per week and a maximum of 8 attacks per day that are severe or very severe in intensity on average
Your current period of cluster headache attacks must be typical of what you usually experience during these episodes
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 method of birth control throughout the study
If you are a man, no birth control requirements are needed
You must be able to understand and sign the consent form, and follow all the requirements and rules of the study

Who Cannot Join the Study?

The study information does not list specific reasons why patients cannot participate in this clinical trial
If you are interested in participating, you will need to discuss with the study team to learn about any health conditions, medications, or other factors that might prevent you from joining
General exclusion reasons in clinical trials may include having certain other medical conditions, taking medications that could interfere with the study drug, being pregnant or breastfeeding if you are a woman of childbearing age, or having allergies to the study medication
The study drug being tested is called candesartan, which is a type of medicine called an angiotensin-receptor antagonist that affects blood pressure regulation in the body

Where you can join this trial?

Verified and Recommended Sites

No sites found in this category

Verified Sites

Site Name	City	Country	Status
Oslo Universitetssykehus HF	Oslo	Norway

Other Sites

Site Name	City	Country
Universitetssykehuset Nord-Norge HF	Tromsø	Norway
St. Olavs Hospital HF	Trondheim	Norway
Helse Stavanger HF	Stavanger	Norway
Nordlandssykehuset HF	Bodo	Norway
Rigshospitalet	Copenhagen	Denmark
Armpbgbx Uhhyqqdwum Hnjoeers	Lorenskog	Norway
Huotv Bayjwo Hl	Bergen	Norway
Hxqtj Mvjap Om Rfgtdev Hd	Aalesund	Norway

Trial status

Country	Status	Recruitment Start
Denmark	Not yet recruiting	17.11.2025
Norway	Not yet recruiting	17.11.2025

Trial locations

Investigated drugs:

Candesartan

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. The medicine works by blocking certain substances in the body that can affect blood vessels. It is being compared to a placebo to find out if it can reduce how often severe cluster headaches occur in people who have episodic cluster headaches.

Episodic Cluster Headache – Episodic cluster headache is a neurological condition characterized by recurring periods of severe headache attacks that occur in cyclical patterns or clusters. During an active period, called a cluster bout, individuals experience multiple headache attacks that typically last between 15 minutes to 3 hours. These attacks occur with remarkable regularity, often striking at the same time each day, and are usually felt on one side of the head, commonly around or behind the eye. The pain is described as extremely intense and sharp, often accompanied by symptoms such as watering of the eye, nasal congestion, or facial sweating on the affected side. Between cluster periods, individuals may experience remission phases lasting months or even years when no headaches occur. The episodic form is distinguished from chronic cluster headache by these pain-free remission periods that last at least three months.

Trial ID:

2025-521470-34-00

Protocol code:

E. CandClus2 V3

Trial Phase:

Therapeutic confirmatory (Phase III)

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A Study of Candesartan Compared to Placebo in Adults with Episodic Cluster Headache to Prevent Severe Headache Attacks

What is this study about?

Who Can Join the Study?

Who Cannot Join the Study?