Some of the views expressed in the following notes on newly approved products should be regarded as preliminary, as there may have been limited published data at the time of publication, and little experience in Australia of their safety or efficacy. However, the Editorial Executive Committee believes that comments made in good faith at an early stage may still be of value. Before new drugs are prescribed, the Committee believes it is important that more detailed information is obtained from the manufacturer's approved product information, a drug information centre or some other appropriate source.

Zomig (ICI Australia)
2.5 mg tablets

Indication: migraine

AMH Section 16.3.2

Serotonin (5HT) is involved in the pathogenesis of migraine. As 5HT receptors are found on cerebral and temporal arteries, drugs acting on these receptors may alter the blood flow.1 Sumatriptan is thought to relieve migraine by acting on the 5HT1D family of receptors. Zolmitriptan also acts on these receptors. In animals, the agonist effect of zolmitriptan on vascular 5HT1 receptors results in vasoconstriction. The release of neuropeptides, such as vasoactive intestinal peptide, is also inhibited.

Zolmitriptan should be taken early in the attack. The drug is rapidly absorbed and, if the patient responds, its effect begins within an hour. If a second dose is required, it should not be taken within two hours of the first 2.5 mg dose.

The maximum dose is 10 mg in 24 hours. The half-life is approximately 3 hours with most of a dose (60%) being metabolised by the liver and then excreted in the urine. One of the metabolites is active. Liver disease reduces the clearance of zolmitriptan.

An Australian report of an international open label study found zolmitriptan to be effective.2 The study included 2058 patients with at least one attack of migraine. It used the higher 5 mg dose which can be tried in patients whose previous attacks have not responded to 2.5 mg. In 80% of patients, the severity of the attacks had reduced by two hours after a dose.

Approximately 35% of patients with severe headache will become pain free. A second dose was required in 32% of all attacks because of headache recurrence.

In this study, 25% of treatments were associated with an adverse event. These included asthenia, nausea, somnolence, dizziness and parasthesia. Other studies have reported sensations of pressure or constriction in the throat, neck or chest. Tachycardia and palpitations have occurred and zolmitriptan is contraindicated in patients with ischaemic heart disease, uncontrolled hypertension or a history of myocardial infarction.

Concomitant administration of zolmitriptan with monoamine oxidase inhibitors or ergotamine is contraindicated. The drug is not affected by paracetamol, metoclopramide or pizotifen.

Sumatriptan and zolmitriptan probably have similar efficacy. Zolmitriptan may be more suitable for patients with allergies to sulfonamides as it does not have a sulfonamide side chain.