This is a double-blinded, randomized, parallel, placebo-controlled phase 2 study to evaluate the safety and efficacy of R-verapamil in the prophylaxis of episodic cluster headache.

Approximately 30 subjects (about 15 per treatment group),will be enrolled and randomized to receive either R-verapamil or placebo for 2 weeks. The study will consist of a 1-week run-in period and a 2-week treatment period (R-verapamil or placebo). The total duration of the study for each treatment group is 3 weeks.

Inclusion Criteria:

• Healthy man or woman between the ages of 18 and 65
• In good health as determined by medical history and medical examination
• Has a diagnosis of episodic cluster headache as defined by the International Classification of Headache Disorders (2nd edition)
• Has a lifetime prevalence of at least 2 prior cluster bouts - Subjects must experience at least 7 attacks/week during the run-in baseline period
• Subjects must have a typical cluster period lasting at least 1 month. Subjects must be present in active cluster period and the expected remaining duration of the cluster cycle must be at least 3 weeks from Baseline Day 1 visit
• Able to differentiate other headache types from cluster headaches
• Is using or agrees to use a medically acceptable form of contraception(female of child-bearing potential)
• Negative urine pregnancy test prior to study entry(female of child-bearing potential)
• Concomitant medication that, in the opinion of the investigator and the patient's general practitioner(GP), do not pose an unacceptable risk based upon the prescribing information for verapamil
• Able to understand and comply with all study requirements
• Written informed consent

Exclusion Criteria:

• Women who are pregnant or lactating
• Subjects who, in the investigators opinion, have a history or have evidence of a medical or psychiatric condition that would expose them to an increased risk of a significant adverse event or would interfere with the assessments of efficacy and tolerability
• Use of any drug or having any medical condition which might interact adversely with, or interfere with the action of, the study medication
• The concomitant use of beta blockers
• The consumption of grapefruit juice
• Allergic to or has shown hypersensitivity to verapamil or agents similar to verapamil
• Abuses opioids or has a history of significant drug or alcohol abuse within the past year as determined by investigator
• Has participated in an investigational drug trial in the 30 days prior to the screening visit
• Has liver or kidney disease
• Has a cardiopathology contraindicating verapamil administration
• Subjects with previous adynamic ileus.
• Subjects with chronic cluster headache
• Use of antipsychotic, antidepressants, lithium or other prophylactic treatment less than one month prior to inclusion