Cluster headaches are often said to be the most painful of all headaches. They have been described as "boring," bearing, burning," "like a hot poker in the eye," and as "suicide headaches."

The use of high dose verapamil has become increasingly common for the prevention of CH, with higher doses than used for heart conditions and hypertension needed. Side effects include atrioventricular block and bradycardia, although how frequently they occur in CH patients is not clear. There are no formal guidelines for the use of verapamil for CH. The authors of this study have developed a protocol, keeping in mind the potential for cardiac complications and reviewed the use of the protocol and the changes seen in EKG readings.

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