Management of migraine in Australian general practice

It is recognised worldwide that migraine is common, underdiagnosed and often inadequately treated. The prevalence of migraine is about 6% in men and 18% in women, as assessed in community surveys.1-3

Modern studies define migraine by criteria published by the International Headache Society.4 A recent community-based study in the United States revealed that, in patients with migraine as defined by these criteria, 52% had not been diagnosed by a doctor, and 57% took only over-the-counter medications.5 Even those patients who had not been medically diagnosed were substantially disabled by migraine, with 24% missing at least a day of work, and 45% having at least a day of reduced productivity in the previous 3 months.

There have been recent advances in both the acute treatment and prophylaxis of migraine.6-8 The introduction of triptans has improved the chances of obtaining swift and substantial relief from migraine attacks for many patients. There has also been recent emphasis on the difficulty in managing frequent migraine attacks. Chronic daily headache (at least 15 headache days per month) occurs in 4% of the population, and in half of these it arises from migraine (“chronic migraine” or “transformed migraine”).9 In some of these cases, the transformation from episodic to chronic migraine results from overuse of acute headache medication, especially narcotic- or codeine-based analgesics, but also ergotamines, triptans and even simple analgesics. There is thus a great need to optimise the use of available effective prophylactic agents.

Our aims in this study were to determine:

• the proportion of Australian general practice patients diagnosed with migraine;

• the usual acute treatments these patients used; and

• the approaches to prophylactic medication, including which drugs were currently used and which had been previously trialled.

The BEACH (Bettering the Evaluation and Care of Health) program is a continuous national study of general practice activity in Australia; sampling and methods have been described in detail elsewhere.10 In summary, each year a random sample of practising general practitioners, drawn from Australian Government GP service claims through Medicare, are invited to participate. About 1000 GPs participate annually, by completing a questionnaire about themselves and their practice, and recording patient morbidity and management details for each of 100 consecutive patient encounters on structured paper forms.

Throughout the year, a series of sub-studies are conducted in conjunction with the ongoing data collection from the GP patient encounters. In each 5-week collection period, about 100 GPs each record information for about 30 patients for each topic. These substudies, known as SAND (Supplementary Analysis of Nominated Data), investigate aspects of patient health not necessarily managed at the encounter (full methodology reported elsewhere).11 Responses are recorded by the GP about the patient, in discussion with the patient. Using a qualified medical practitioner to record morbidity in conjunction with patient self-report may provide a more accurate classification of patients’ health problems than self-report alone.12,13 Two SAND subsamples — June–July 2005 and December 2005–January 2006 — were used to investigate the prevalence of migraine among patients attending general practice, frequency of migraine attacks, current and previous prophylaxis and current acute medications.

The number of questions that could be asked was limited by the space available on the recording form. Each GP was asked to record whether or not, in his or her opinion after speaking with the patient, each of 30 consecutive patients suffered from migraine attacks. If the response was “no”, the questions ended. Where a “yes” response was recorded, the GP was asked to report the usual migraine frequency per month (four tick-box options: < 1, 1, 2 and ≥ 3). Prophylactic medications and current medications for acute treatment were described in free text, and the reason for discontinuation of previous prophylaxis was requested with a series of tick boxes (lack of efficacy, cost, withdrawal after successful treatment, and side effects).

Responses were received for 5663 patients from 191 GPs. The GPs reported that 649 patients (11.5%) had been diagnosed (on that day or previously) with migraine (Box 2). Prevalence was significantly higher among female (14.9%) than among male (6.1%) patients (P < 0.0001). Migraine prevalence was least among children aged under 15 years (1.2%) and was highest among patients aged 25–44 years (17.6%), followed by those aged 45–64 years (15.4%) (Box 2).

Data on migraine frequency were available for 617 of the 649 patients with diagnosed migraine. More than three-quarters (77.1%) of these 617 patients reported usual migraine frequency as one or fewer attacks per month. An average of two attacks per month was reported by 10.5%, and three or more per month by 12.3% (Box 3).

Prevalence of migraine: In this study, GPs reported that 14.9% of female patients and 6.1% of male patients experienced migraine. Community-based studies from around the world indicate that the prevalence of migraine is about 18% in women and 6% in men.1-3 One might conclude that migraine is not substantially underdiagnosed in Australia. However, at least a proportion of migraineurs require prescription medication for their condition, increasing the likelihood of presenting to a GP, and the figures might thus be skewed to recording a higher-than-true prevalence of migraine. Conversely, patients with undiagnosed migraine would not be recorded by our methodology. Based on experience from other countries, we would expect that many cases of migraine would be misclassified as other forms of headache, both by patients17 and by their treating doctors.18

Frequency of migraine: 12.3% of patients reported three or more migraines per month, while 77.1% reported one or fewer per month. These findings contrast with previous data. Stewart et al reported a median frequency of 1.5 per month.19 Community-based studies of chronic daily headache (defined as 15 or more headache days per month) indicate a prevalence of 4%, with about half of these cases being migrainous.9 On this basis, the reporting of frequent migraine in our study may be below that expected and may reflect misclassification of frequent migrainous headaches as tension-type headaches, as has been documented in other populations.18

Use of acute medication: Most patients reported using simple analgesics available over the counter. This is in keeping with published guidelines. For acute drug treatment of migraine, the NPS recommends analgesia or NSAIDs, with an anti-emetic if necessary, for mild to moderate migraine.16 For severe migraine, or where there is no response to analgesia, the recommendation is a triptan or ergotamine. While guidelines emphasise the need for caution with opioids, especially combined analgesics,20 these accounted for 38% of acute treatments. This suggests the need for further education not only of GPs, but also of the general public, as many combined analgesics are available over the counter.

Use of prophylactic medication: Australian Therapeutic Guidelines recommend regular preventive treatment if the patient continues to experience more than two or three acute attacks of migraine per month.20 Other experts highlight that some patients with prolonged or disabling attacks might warrant prophylaxis with a lower attack frequency.7 About 20% of the patients in our study who had three or more migraines per month were currently receiving prophylaxis; of those not taking prophylaxis, 33% had previously tried it but stopped, while 67% had never received such treatment. This finding suggests a reluctance to use such treatments and raises the question of why this should be. We can only speculate on this. GPs may underestimate the impact that frequent migraine has on patients. GPs or patients may be satisfied with the control provided by acute medications. They may be suspicious of side effects in available medications, or doubt their efficacy. In this study, when preventive agents were discontinued, it was because of lack of efficacy in 46% of patients and side effects in 28%.

Choice of prophylactic medication: The American Academy of Neurology has published an influential practice parameter and evidence-based review of migraine treatment.15 The classification of preventive treatments outlined in Box 4 is based on this. Pizotifen is not available in the US and is not listed in that review; however, based on review of evidence (predominantly small and, by modern standards, poorly designed trials from the 1960s and 1970s21), it would fall into treatment Level 2. In the current study, pizotifen and propranolol were the predominant choices with regard to current prophylactic therapy (31% and 22% of patients, respectively) and previous prophylactic therapy (51% and 20% of patients, respectively). Other medications from treatment Levels 1 and 2 were rarely used. The failure of GPs to prescribe drugs other than pizotifen or propranolol may suggest a lack of familiarity with alternatives that are well supported by published data and guidelines, or lack of confidence in using these drugs. However, GP prescribing of valproate and topiramate for migraine may be inhibited by other factors: the NPS states, “While the anti-epileptics valproate and topiramate have demonstrated efficacy, valproate is not approved for migraine prophylaxis and topiramate is not available through the PBS [Pharmaceutical Benefits Scheme] for its migraine prevention indication”.16 Lack of a PBS subsidy results in greater out-of pocket expense for the patient. GPs are more likely to prescribe new drugs when they have been strongly promoted by the pharmaceutical industry;22 lack of Therapeutic Goods Administration and/or PBS listing of Level 1 drugs for migraine, and, in many cases, expiry of patent may inhibit pharmaceutical promotion of these drugs.

Of particular concern was the use of acute agents (analgesics, triptans and ergotamines) as prophylaxis, with 9% of patients reporting using such an approach. The risk of medication-overuse headache is high in these circumstances,23 and the American Academy of Neurology practice parameter notes that many experts limit the use of ergotamines, triptans and opioids to two headache days per week for this reason.15 Regular daily use of these agents is clearly inappropriate.

A critique of the current management of migraine by Australian GPs is provided in Box 6.