Regular medication to reduce the frequency and/or severity of attacks is recommended for moderate to severe migraine when 2–3 or more attacks occur per month.
PROPHYLAXIS OF MIGRAINE
Regular medication to
reduce the frequency and/or severity of attacks is recommended for moderate to severe
migraine when 2–3 or more attacks occur per month. Diverse classes of drugs are
used but none is effective in all cases, and none abolishes the attacks
totally. It may be prudent to discontinue pophylaxis every 6 months to check
whether its continuation is needed or not. It is important to avoid the
precipitating factor(s).
Β-Adrenergic
blockers
Propranolol is the most commonly used
drug: reduces frequency as well as severity of attacks in upto 70% patients.
Effect is generally seen in 4 weeks and is sustained during prolonged therapy.
The starting dose is 40 mg BD, which may be increased upto 160 mg BD if
required. The mechanism of action is not clear; that it is due to β adrenergic blockade
has been questioned. Other nonselective (timolol) and β1 selective
(metoprolol, atenolol) agents are also effective, but pindolol and others
having intrinsic sympathomimetic action are not useful.
Tricyclic antidepressants
Many tricyclic compounds of which amitriptyline has been most
extensively tried (25–50 mg at bed time) reduce migraine attacks. It is
effective in many patients but produces more side effects than propranolol. It
is not known whether its 5HT (and other monoamine) uptake blocking property is
causally related to the prophylactic effect. The antimigraine effect is
independent of antidepressant property, but this class of drugs are better
suited for patients who also suffer from depression.
Calcium Channel Blockers
Verapamil was found to reduce
migraine attacks, but was judged inferior to propranolol. Flunarizine is a relatively weak Ca2+ channel blocker that also inhibits
Na+ channels. It is claimed to be as effective as propranolol, but convincing
proof is lacking. Frequency of attacks is often reduced, but effect on
intensity and duration of attacks is less well documented. It is claimed to be
a cerebroselective Ca2+ channel blocker; may benefit migraine by reducing
intracellular Ca2+ overload due to brain hypoxia and other causes. Side effects
are sedation, constipation, dry mouth, hypotension, flushing, weight gain and
rarely extrapyramidal symptoms.
Dose: 10–20 mg OD, children
5 mg OD, NOMIGRAIN, FLUNARIN 5 mg, 10
mg caps/tab.
Anticonvulsants
Valproic acid (400–1200 mg/day) and gabapentin (300–1200 mg/day) have
some prophylactic effect in migraine. The newer drug topiramate has recently
been approved for migrain prophylaxis. A 50% reduction in the number of attacks
in half of the patients was noted in 2 randomized trials. Start with 25 mg OD
and gradually increase to 50 mg OD or BD. Efficacy of anticonvulsants in
migraine is lower than that of β blockers. They are indicated in patients
refractory
to
other drugs or when propranolol is contraindicated.
5HT Antagonists
The
prophylactic effect of methysergide and
cyproheptadine is less impressive than β blockers. They are
seldom used now for migraine.
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