In this essay we will discuss about the nonspecific and specific drugs used for the treatment of migraine.
Nonspecific Drugs:
Nonspecific drugs are NSAIDs, metoclopramide and pro-chloperazine.
i. NSAIDs :
NSAIDs are first-line treatment that is most effective early in the course of an attack. The headache often responds to oral administration of simple analgesics such as paracetamol or aspirin or tolfenamic acid (particularly). Ketorolac (IM or IV) is useful in the acute treatment of recalcitrant headaches.
ii. Metoclopramide:
Metoclopramide is generally given 30 minutes before the analgesic to prevent vomiting and increase the rate of gastric emptying and thus hasten the absorption of the analgesic.
iii. Prochlorperazine (IV):
Prochlorperazine (IV) may terminate migraine and help to alleviate nausea. Acute dystonic reactions and hypotension are potential side effects.
Specific Drugs :
Specific drugs are triptans and ergot alkaloids. These drugs are used when nonspecific therapy fails, which is the case in about 20% of patients. They are not analgesics but relieve migraine headache by causing constriction of the dilated blood vessels surrounding the brain and on the trigeminal nerve.
i. Triptans:
Triptans stimulate 5-HT (serotonin) receptors in the wall of the dilated blood vessels, resulting in vasoconstriction. They are effective abortive medications that are available in-multiple formulations and may be effective even in a protracted attack.
Sumatriptan is given by SC injection or as a nasal spray or orally and is effective for treatment of a migraine attack in about 65% of patients. Side effects are rare. It is contraindicated in patients with coronary artery disease, cerebrovascular disease, uncontrolled hypertension and neurological deficits. Naratriptan, zolmitriptan are amongst other triptans which are similar and are given orally.
ii. Ergot Alkaloids:
Ergot alkaloids are obtained from a fungus that grows on rye. Ergot contains many pharmacologically active substances and the alkaloid ergotamine and its derivative dihydroergotamine (DHE) are used for aborting migraine headaches.
Ergotamine:
Ergotamine stimulates α1 adreno-receptors and causes vasoconstriction, particularly of small arteries. The use of ergotamine has been limited due to its toxicity and the availability of triptans.
Dihydroergotamine (DHE):
Dihydroergotamine (DHE) is a potent vasoconstrictor with minimal peripheral arterial constriction, which makes it more suitable than ergotamine for aborting migraine headache, since the major toxicity of ergot lies in its peripheral vasoconstriction effect. It is given parenterally or intranasally.
Side effects like nausea and vomiting can be controlled by metoclopramide. Chronic use may lead to serious toxicity which includes angina pectoris, limb claudication, ergotamine headache, dependency and even gangrene. Vasoconstriction is increased in patients taking β blockers. Ergot alkaloids are contraindicated in coronary disease and pregnancy.
Prevention of Migraine Attacks:
The drugs are used on a continuous basis as a preventive measure, if the attacks occur more than once a week. There is no clear-cut best drug and the choice lies on the patient’s acceptability.
The following groups of drugs are used to prevent migraine attacks:
i. β blockers:
β blockers are the most commonly used to prevent or reduce the attacks. They probably act by reducing vasodilatation. All β blockers are equally effective and can be used provided there is no contraindication to their use. They should not be used in patients receiving ergot alkaloids.
ii. Pizotifen:
Pizotifen is an antihistamine and serotonin antagonist and prevents migraine attacks by reducing the constriction and dilation of blood vessels. It affords good prophylaxis but may cause weight gain.
iii. Anti-Epileptics:
Sodium valproate may be effective in preventing migraine attacks. Rarely, it may cause severe hepatic damage, pancreatic toxicity and a reduction in blood platelets. It is contraindicated in pregnancy.
iv. Antidepressants:
Dosulepin and amitriptyline may be used even though the patient is not suffering from depression.
v. Calcium Channel Blockers:
Verapamil and nifedipine have also been found useful for migraine prophylaxis.