Cluster headache is a primary headache disorder characterized by attacks of unilateral headache of short duration and severe pain intensity. There is an unmet need to understand the underlying disease mechanisms that will ultimately lead to the development of disease-specific medicines. Until now, it has been suggested that the calcitonin gene-related peptide (CGRP) plays a major role in the initiation of a cluster headache attack, possibly involving the ATP-sensitive potassium channels. The current study aims to determine whether the opening of ATP-sensitive potassium channels triggers cluster headache attacks in patients with cluster headache.

Inclusion Criteria:

• Cluster headache patients meeting ICHD-3 criteria for episodic and chronic cluster headache of either sex. Patients were defined as having episodic cluster headache in the active phase when they had usual attacks within the last 30 days, episodic cluster headache in the remission phase when they were attack-free for at least 30 days, or chronic cluster headache when they had not had more than 30 consecutively attack-free days over the last 12 months or longer.
• Weight between 50 and 100 kg.
• All preventive medications, except steroid treatments or greater occipital nerve blockade within 30 days, were allowed with stable dosing.
• Negative urinary HCG at baseline.

Exclusion Criteria:

• Primary headache types except above.
• Secondary headache disorders, according to ICHD-3.
• Headache at baseline.
• Anamnestic information or clinical signs of (at inclusion date) hypertension (systolic blood pressure >150 mmHg and/or diastolic blood pressure >100 mmHg) or hypotension (systolic blood pressure < 90 mmHg and/or diastolic blood pressure < 50 mmHg)
• Known severe or treatment-requiring cardiovascular disease including cerebrovascular disease.
• Anamnestic or clinical evidence of mental disorder or substance abuse.
• Anamnestic or clinical evidence of any disease considered by the investigating physician to be relevant to participation in the study.
• Pregnant or lactating women.