Medications

Calcium-channel blockers, commonly used to treat heart disease, are important agents for preventing cluster headaches. Verapamil (Calan) is the standard calcium-channel blocker used for headache prevention. Constipation is a common side effect. No one taking any calcium-channel blocker should withdraw abruptly, because such action could dangerously increase blood pressure. Overdose can cause dangerously low blood pressure and slow heart beats. It should be noted that drinking grapefruit juice or eating grapefruit with these drugs could enhance their potency, sometimes to toxic levels that can cause heart failure in patients with heart disease.

Lithium

Lithium (Eskalith, Lithane, Lithobid, Lethonate, Lithotabs), commonly used for bipolar disorder, is beneficial for cluster headaches and is the most effective agent for chronic cluster patients. One small study suggested that lithium may act directly on the nerve clusters affecting the circadian rhythm and slow down the cycle of this "biologic clock." (There is some evidence that cluster headaches are caused by a failure in the biologic clock.) The patient usually experiences benefits within two weeks, and often within the first week. It is not clear how or why it works for cluster headache patients. Lithium may be used alone or with other drugs.

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Toxic Effects. Minor toxic reactions include the following:

• Trembling hands.
• Nausea.
• Increased urine output.
• Some loss of coordination.

More severe reactions, which occur at higher blood levels, are the following:

• Convulsions.
• Uncontrolled jerky movements in arms and legs.
• Blurred vision.
• Vomiting.
• Stupor.
• Coma.