Nonsteroidal anti-inflammatory drugs (NSAIDs) are favoured for patients with mild to moderately severe migraine attacks, and these are also sometimes combined with metoclopramide. In addition, patients may be switched haphazardly from one to the other NSAID in an effort to find one that works for them.

Both the NSAIDs and 5-HT agonist drugs are also used preventatively, with limited success. In one trial naproxen, a NSAID, only prevented half the patients (52 per cent) from developing severe headaches, although all patients receiving the drug found that the severity and duration of headaches, the frequency of nausea and vomiting, and the use of analgesic medication were all reduced (Neurology, 1985; 35:1304-10). However, it is recommended that NSAIDs are not used for prolonged periods, due to the risk of gastrointestinal ulceration and bleeding which effectively negates their prophylactic role.

Of the 5-HT agonist drugs, those considered to be the most effective are methysergide and amitriptyline, but again both have worrying side effects. Long term treatment with methysergide can cause fibrosis, such as inflammation and scarring of tissue of the lungs, heart valves and ureters (tubes which carry urine from the kidneys to the bladder), possibly resulting in organ failure. Amitriptyline can cause weight gain, drowsiness, blurred vision and irregular heartbeat.

At the other end of the scale, we have calcium channel blocking drugs which are used to prevent migraine, although overall their effect has been unimpressive. They have the opposite effect to the 5-HT agonists, in that they cause "vasodilation", increasing blood flow by widening blood vessels. For this reason they are often used to treat angina and heart arrhythmias.

However, although they may decrease the frequency of migraine attack, they seem to have little effect on severity and have even been known to bring on headaches that are so severe they are indistinguishable from migraines! (N Engl J of Med, 1993; 329 (20):1481.)

Then there's sodium valproate, a drug more commonly used to treat epilepsy. This has been shown to be moderately effective in preventing migraine and reducing the frequency, severity and duration of severe attack, although it's not really known why this should be so (Cephalalgia, 1992; 12:81-4). And yet again there are some serious side effects including hair loss, weight gain, potentially fatal liver problems and neural tube defects in fetuses.

Danazol is a drug commonly used to treat endometriosis, yet despite some very disturbing side effects may also be used to prevent hormonally related migraines. One study found that out of 131 women with hormonally related migraines that had not responded to standard medication, half experienced profound relief after a year.

But what danazol actually does is induce a post-menopausal state including all the usual side effects.

Tamoxifen, a drug used in the prevention and treatment of breast cancer, is also reported to be effective in preventing hormonally related migraines (The Lancet, 1986; 2: 1344).

However, the side effects and risks associated with this drug are enough to make even those with breast cancer think twice about taking it. Tamoxifen increases the risk of endometrial cancer about five fold (The Lancet, 11 January 1992), and tamoxifen patients have experienced abnormal vaginal bleeding, hyperplasia (excessive cell formation) polyps and endometriosis (BMJ, October 26, 1991).