Prescribing Notes

Migraine

Initial management of migraine should include a discussion of previously tried medications and identification of trigger factors such as dietary, physical or emotional stimuli.

TREATMENT
Symptomatic pain relief using simple analgesics such as aspirin or paracetamol can be optimised by taking a high enough dose early in an attack, and in a soluble form for enhanced absorption. GI symptoms may be managed using anti-emetics.

Where migraine proves refractory to simple analgesics, a 5HT1-agonist (triptan) can be tried. They can relieve migraine at any stage of the attack, but are best given early. All triptans provide effective relief from accompanying symptoms of nausea, photophobia and phonophobia but this class of compound has been associated with coronary vasospasm and therefore should not be used in patients with ischaemic heart disease, unstable angina or unrecognised cardiac disease. Sensations of tightness or pressure over the precordium which may also extend to the throat and limbs have been reported. If these persist or are severe, they should be fully investigated before further doses are given.

Similarly an ergot alkaloid may be effective if given within 60-90 min of onset. Overuse of ergot derivatives can exacerbate symptoms and lead to gangrene through vasoconstriction of peripheral vessels. Therefore, the recommended dose periods should not be exceeded. Peripheral vasoconstriction also contraindicates use of ergot preparations in patients with chronic heart disease, peripheral vascular disease, hypertension, renal and hepatic disease. Uterine contractile activity excludes their use in pregnancy. Other side effects include nausea, vomiting, leg cramps, abdominal pain and paraesthesia. It should be remembered that ergotamine interacts with β-blockers and 5HT1-agonists and therefore should not be given concomitantly for migraine.

MEDICATION OVERUSE
Excessive use of headache medications may lead to an increased frequency of headache, potentially requiring withdrawal of treatment. The possibility of medication overuse headaches should be considered in patients who have frequent or daily headaches despite (or because of) the regular use of headache medications.

PROPHYLAXIS
Preventative treatment is recommended for patients who have more than two attacks per month or poor response to acute therapy.

β-blockers are effective but their side effects and contraindications should be carefully considered before prophylactic use.

Erenumab is the first in a new class of migraine prophylactics known as calcitonin gene-related peptide (CGRP) antagonists. CGRP is a neuropeptide that modulates nociceptive signalling and a vasodilator that has been associated with migraine pathophysiology. Erenumab is indicated for use in adults who have at least four migraine days per month; it is given as a subcutaneous injection once every four weeks.

Other prophylactic treatments that can be tried include amitriptyline and pizotifen. Cyproheptadine can be tried in refractory cases. Side effects common to both pizotifen and cyproheptadine include increased appetite, weight gain and fatigue. Topiramate may be used for the prophylaxis of migraine headache in adults experiencing three or more migraine attacks per month or whose daily routine is significantly disrupted. Botox (botulinum toxin type A) is indicated for the prophylaxis of chronic migraine in adults who experience headaches on at least 15 days per month, of which at least 8 days are with migraine. By blocking the release of neurotransmitters, it is thought to suppress peripheral pain signals to the central nervous system. Treatment with topiramate or Botox should be initiated under specialist care. The efficacy of clonidine in migraine prophylaxis is questionable. Side effects include sedation, dry mouth, bradycardia, constipation and contact dermatitis.