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P A R T 4  Drugs acting on the central and peripheral nervous systems

and continued state of arterial dilation are not clearly understood, but they may be related to the release of bradykinins or serotonin, or as a response to other hormones and chemicals. ANTIMIGRAINE AGENTS For many years, the one standard treatment for migraine headaches was acute analgesia, often involving an opioid, together with control of lighting and sound and the use of ergot derivatives. In the late 1990s, a new class of drugs, the triptans, was found to be extremely effec- tive in treating migraine headaches without the adverse effects associated with ergot derivative use. Because these agents are associated with many systemic adverse effects, their usefulness is limited in some people (see Box 26.5). Table 26.2 includes additional information about each class of antimigraine agents. E rgot derivatives The ergot derivatives cause constriction of cranial blood vessels and decrease the pulsation of cranial arteries. As a result, they reduce the hyperperfusion of the basilar artery vascular bed. Available ergot derivatives include ergotamine ( Cafergot ) (no longer available in Australia). Therapeutic actions and indications The ergot derivatives block alpha-adrenergic and sero- tonin receptor sites in the brain to cause a constriction of cranial vessels, a decrease in cranial artery pulsa- tion and a decrease in the hyperperfusion of the basilar the mother and fetus. Women of childbearing age should be advised to use contraception while they are taking these drugs. Women who are breastfeeding should be encouraged to find another method of feeding the baby because of the potential for adverse drug effects on the baby. OLDER ADULTS Older adults are more likely to have chronic diseases such as cardiovascular disease or renal or hepatic impairment that would be exacerbated by the antimigraine drugs.They should be used with extreme caution in older adults.The older adult should be encouraged to take the least amount of the drug possible and should be monitored closely for any sign of chest pain, MI or acute vascular changes. Safety measures are extremely important with the older adult. If the person is in an institutional setting, side rails, assistance with moving and careful monitoring should be used.

Gender considerations

BOX 26.4

Migraines are generally classified as common or classic. Common migraines, which occur without an aura, cause severe, unilateral, pulsating pain that is frequently accompanied by nausea, vomiting and sensi- tivity to light and sound. Such migraine headaches are often aggravated by physical activity. Classic migraines are usually preceded by an aura—a sensation involving sensory or motor disturbances—that usually occurs about half an hour before the pain begins. The pain and adverse effects are the same as those of the common migraine. It is believed that the underlying cause of migraine headaches is arterial dilation. Headaches accompanied by an aura are associated with hypoperfusion of the brain during the aura stage, followed by reflex arterial dilation and hyperperfusion. The underlying cause predisposition to migraine headaches may be related to the vascular sensitivity to hormones. Some women can directly plot migraine occurrence to periods of fluctuations in their menstrual cycle.The introduction of the triptan class of antimigraine drugs has been beneficial for many of these women. Headache distribution Headaches are distributed in the general population in a definite gender-related pattern. For example: • Migraine headaches are three times more likely to occur in women than men. • Cluster headaches are more likely to occur in men than in women. • Tension headaches are more likely to occur in women than in men. There is some speculation that the female

Drug therapy across the lifespan

BOX 26.5

Antimigraine agents CHILDREN None of the drugs used to treat migraines are

recommended for use in children.The ergot derivatives can have many adverse effects in children, and there is not enough clinical experience with triptans to recommend them for use in children. ADULTS Adults requesting treatment for migraine headaches should be carefully evaluated before one of the antimigraine drugs is used to ensure that the headache being treated is of the type that can benefit from these drugs. PREGNANCY AND BREASTFEEDING The ergots and the triptans are contraindicated during pregnancy because of the potential for adverse effects in