Walsh & Hoyt: Headache Attributable to a Substance or Its Withdrawal

Medication overuse headache (MOH), also called analgesic rebound headache, was first described in 1951 by Peters and Horton. Potentially all analgesic drugs, including over-the-counter agents, may lead to MOH. The most common cause of migraine occurring 15 or more days a month, or a mixed migraine/tension-type headache, is medication overuse. In headache subspecialty practices, medication overuse is the most common cause of intractability. The IHS criteria define MOH primarily by treatment days per month. The regularity of treatment is important, as well; bunching of treatment days with long periods of no medication intake is less likely to result in MOH. The headache is generally dull, constant, and diffuse. The headache may vary in severity and location. There is evidence of tolerance to analgesics over time, and withdrawal symptoms are observed when medications are discontinued abruptly. Many patients with MOH have a preexisting headache type (usually migraine); their daily headaches may be a mixture of chronic daily headache with superimposed episodic migraine attacks. Recent data suggest that triptans will soon be recognized as the most common group of medications to cause MOH. Indeed, the second edition of IHS has a separate entry for triptan overuse. Patients with triptan overuse headache typically describe a unilateral, pulsating headache with migrainous qualities.