Migraine Prophylaxis
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Direct answer
Start a preventive when migraine attacks run to about four or more headache days a month, when attacks are prolonged, disabling or risky (hemiplegic or migraine with brainstem aura), or when acute medicines are being overused — and the classical first-line choices are propranolol, topiramate, amitriptyline or flunarizine, with valproate reserved for selected patients who can avoid pregnancy. Each drug is given a fair trial of eight to twelve weeks at an adequate dose before judging failure, and after six to twelve months of success the dose is tapered to see whether remission sustains.
What you must remember
- Indication threshold: commonly four or more headache days per month (some guidance accepts fewer with high disability), measured against acute-medication frequency to prevent medication-overuse headache.
- Propranolol 40–160 mg daily (long-acting) — avoid in asthma, heart block, hypotension; a first-line standard alongside timolol and metoprolol.
- Topiramate 25 titrated to 50–100 mg daily — weight loss, paraesthesia, nephrolithiasis, word-finding difficulty, and teratogenicity; ineffective as concurrent acute therapy substitute.
- Amitriptyline 10–75 mg at night — best when insomnia or tension-type overlay coexists; anticholinergic caution in the elderly.
- Flunarizine 5–10 mg at night — an Indian outpatient favourite; adverse effects are sedation, weight gain, depression and drug-induced parkinsonism, which makes it unsuitable in the elderly and the depressed.
- Valproate works but is avoided in women of childbearing potential; candesartan and venlafaxine are useful alternatives with comorbidity tailoring.
- CGRP monoclonal antibodies (erenumab, fremanezumab, galcanezumab) are for refractory or contraindicated patients, subcutaneously monthly, with constipation and injection-site reactions the main issues.
- Trial discipline: eight to twelve weeks at adequate dose before declaring failure; combine only one preventive at a time; taper after six to twelve months of benefit.
- Acute-attack hygiene still applies — triptans early in the attack, limited to under about ten days a month — because prophylaxis and overuse rescue must travel together.
Matching the drug to the whole patient
A 34-year-old software engineer has eight migraine days a month; she is overweight, has PCOS, sleeps poorly, and her attacks respond to sumatriptan but recur. Run the decision as a matching exercise rather than a memorised list. Comorbidity first: her overweight points to topiramate (the one preventive that reduces weight), her poor sleep would also suit amitriptyline at night, propranolol fits neither profile especially, and flunarizine's weight gain argues against it here. Fertility next: she uses contraception but topiramate is teratogenic, so counselling is explicit; were she actively planning pregnancy, amitriptyline or propranolol would lead instead, and valproate would never be first choice in a woman of childbearing age. Trial mechanics: topiramate started at 25 mg nightly and titrated over weeks to 50–100 mg, with a diary reviewed at eight to twelve weeks — because most "failures" in practice are under-dosed or under-tried. If two adequate trials fail, the ladder advances to CGRP monoclonal antibodies, and compounded triggers — irregular meals, screen posture, sleep debt — are addressed in parallel. Success at nine months is not lifelong prescription: the dose is tapered to test remission, and the diary continues, since the commonest reason for "prophylaxis failure" on re-referral is actually medication-overuse headache layered on top.
Where students slip
Two predictable errors dominate. The first is quoting one drug for all patients — the examiner wants the matching logic: beta-blocker in the anxious hypertensive, topiramate in the obese, amitriptyline in the insomniac, flunarizine where cost matters but never in depression or the elderly. The second is impatience in the numbers: judging a preventive at two weeks, or forgetting the eight-to-twelve-week adequate-trial rule and the six-to-twelve-month taper rule. The Indian viva twist is flunarizine — examiners know it is a regional mainstay and expect its parkinsonism and depression adverse effects unprompted.
Frequently asked questions
When is migraine prophylaxis indicated?
At around four or more headache days per month, with prolonged or disabling attacks, contraindication or failure of acute therapy, high MIDAS-type disability, or high-risk subtypes such as hemiplegic migraine.
Which prophylactic suits an obese migraineur?
Topiramate, titrated to 50–100 mg daily, for its weight-attenuating effect — with counselling on teratogenicity and its paraesthesia and renal-stone adverse effects.
What are the adverse effects of flunarizine?
Sedation, weight gain, depression and drug-induced parkinsonism — avoid it in older patients and those with depressive illness.
How long before a preventive is judged ineffective?
Adequate dose for eight to twelve weeks; most apparent failures reflect under-dosing or too short a trial.
When are CGRP monoclonal antibodies used?
For refractory migraine after failures of or contraindications to standard preventives, given as monthly subcutaneous injections, with constipation and injection-site reactions the main adverse effects.