Analgesic headache

A common, treatable condition that deserves more attention

“Do no harm” is the first commandment for clinicians, but effective drug treatment cannot be given without exposing patients to the risk of side effects. One side effect quite often observed in the treatment of headache is rarely seen in other conditions: the treatment may aggravate the symptom for which it has been given. Ergotamine, narcotics, and even mild analgesics may all aggravate tension headache and migraine when taken daily.1 2

Ergotamine has a relatively short half life in plasma but a longlasting effect on arteries,3 and its frequent use may induce almost permanent vasoconstriction.4 Headache induced by ergotamine is of two types.5 One type is associated with daily use of ergotamine and is present almost constantly but fluctuates in intensity and characteristics: sometimes it fulfils the criteria for migraine, but at other times it does not. The second type is associated with sudden discontinuation of daily ergotamine, and this may cause a severe and protracted attack of migraine. Vasodilatory counteracting mechanisms that develop during chronic use of ergotamine are left unopposed when the drug is withdrawn, and this may explain the ergotamine withdrawal headache. The only effective treatment is to start ergotamine again, so the patient is caught in a vicious circle of use and abstinence from the drug. Admission to hospital may be needed to break this pattern.

Sumatriptan, the specific remedy against migraine that was introduced recently, may theoretically cause the same problems. Treatment with sumatriptan has been shown to ameliorate ergotamine withdrawal headache.6 In most migraine centres a few patients have been found to be misusing sumatriptan,7 but the drug seems only rarely to aggravate headache or migraine in people who are not already misusing another drug. The pharmacological differences between ergotamine and sumatriptan probably explain why sumatriptan rarely causes drug induced headache and why stopping overconsumption is relatively easy.

In Denmark narcotics have been widely used for migraine. As a result, each year, an estimated 13 people per million have become dependent on these drugs after taking them for migraine.8 Recently the problem has been brought under control by education of the profession. Centrally acting analgesics should not be used to treat migraine or tension headaches.

Large daily doses of mild analgesics may also aggravate headaches. Experience in Germany, Switzerland, Britain, and the United States has shown that mixed analgesic compounds containing aspirin or paracetamol in combination with a barbiturate, a benzodiazepine, or a narcotic such as dextropropoxyphene are probably the strongest inducers of chronic analgesic headache.6 Whether pure aspirin or paracetamol may do the same is less certain.

The clinical importance of analgesic headache is shown by the number of studies reporting substantial improvement in the frequency or severity of headaches after daily analgesics are stopped.1 3 4 6 Nevertheless, the mechanisms of this type of headache remain unclear. Analgesics induce headache only in people who suffer headaches—not when given for other diseases such as rheumatoid arthritis.1 6 Either the pain pathways in patients with headaches are specially prone to sensitisation by daily analgesics or the analgesic headache must be a state of psychological dependence. Analgesics on a fixed schedule are more effective in treating chronic pain than analgesics given on demand; but virtually all patients with headaches who overconsume analgesics take their drugs on demand—constantly focusing their attention on the headache and the drug. Increased attention is known to increase sensitivity to painful stimuli and so might be a relevant mechanism.9 A double blind, placebo controlled withdrawal experiment is required, but unfortunately such a study has not been done.

Despite the deficiencies in our knowledge of the mechanisms of analgesic headache several recommendations for its prevention can be made with confidence.6 Patients with headaches should never take analgesics every day: the maximum should be set at 15 days a month. Ergotamine should probably not be taken more than 10 times a month, and the same (or perhaps a slightly higher frequency) applies to sumatriptan. Narcotics should not be used at all. Compound analgesics should be avoided as far as possible. If these simple precautions were all followed new cases of analgesic headache should become rare.

Finally, what can be offered to the many patients who already suffer from analgesic headache? A careful explanation of the mechanisms of the headache and its prevention, frequent consultations, and psychological support should make it possible for the drug to be withdrawn in most cases. Once withdrawal has been achieved prognosis is favourable—the relapse rate, even in cases of severe overuse of ergotamine, is only around 30%.10 This unpleasant and often disabling condition deserves more attention.