Community pharmacists are well placed to help prevent and manage the debilitating problem that is medication overuse headache.

Medication overuse headache (MOH) can be debilitating. Previously known as rebound headache, drug-induced headache and medication misuse headache,¹ people with MOH experience headaches:
• On 15 days or more a month
• For four or more hours a day
• For three or more months.

As many as 30-70 per cent of patients referred to specialised headache centres may have MOH.^1,2 The condition can lead to absenteeism, A&E visits, hospital admissions and unnecessary diagnostic tests.¹ As a result, the costs of managing MOH may be three times greater than those for migraine and more than 10 times higher than those associated with tension-type headache.

Absenteeism and reduced productivity account for about 90 per cent of the costs² with a review concluding that “MOH is likely to be one of the most if not the most costly neurological disorder known”.¹

Common problem

About 1-2 per cent of the general population suffers from MOH.1 Women are about three to four times more likely than men to develop MOH – which typically emerges when patients are in their 40s – but up to 0.5 per cent of children and adolescents may have MOH.3 Most people with MOH originally suffered from migraine (65 per cent) or tension-type headache (27 per cent).¹ MOH can transform episodic migraine to chronic migraine.¹

Healthcare professionals should consider MOH in every patient who presents with chronic headaches. The location of pain in MOH frequently differs from the original headache disorder, which may offer a diagnostic clue. Patients with episodic migraines who develop MOH may, for instance, describe headaches in their forehead, temples or back of the head.

The headache may be unilateral, bilateral or both. Patients may believe they have more than one type of headache and expect healthcare professionals to explain the variability. Most people with MOH also experience neck pain, which can lead to misdiagnosis and ineffective treatment.¹

Several groups of people seem to be at increased risk of developing MOH. For instance, those who regularly use tranquilisers (odds ratio [OR] 5.2) and people with anxiety or depression, as well as musculoskeletal and gastrointestinal complaints, are five times (OR 4.7) more likely to develop MOH. People who use analgesics for any condition (OR 3.0) and those who are inactive (OR 2.7 versus high activity) are at a three-fold increased risk of developing MOH. Pharmacists should advise smokers to quit: daily smoking increased MOH risk by 80 per cent.¹

Broadly, five groups of headache medications can cause MOH: simple analgesics, non-steroidal anti-inflammatory drugs, triptans, opioids and ergotamine.4 People taking triptans seem to be particularly vulnerable to MOH. On average, people need to overuse triptans for 1.7 years before developing MOH. This compares to 2.7 years for ergotamine and 4.8 years for simple analgesics.

Similarly, the average frequency of use during a month in those who developed MOH was lowest for triptans and highest for simple analgesics.³

Often, MOH seems to arise from a combination of changes produced by the overused drug, that increase the sensitivity of pain pathways ascending from the body to the brain, and weaken the pathways descending from the brain that inhibit pain.¹

Overusing triptans, for example, may induce ‘latent sensitisation’ – i.e. nerves become more likely to trigger pain, which results in increased susceptibility to migraine triggers.

Overusing paracetamol may increase the activity of some parts of the brain (cortical excitability).¹

Triptans and paracetamol can alter levels of serotonin, which is important in pain processing and might contribute to the association between anxiety, depression and MOH.²

In other cases, MOH may arise because the patient is predisposed to dependency:⁵ up to 65 per cent of people with MOH show dependency-related behaviours, for instance.² Many patients continue taking analgesics despite the painkillers having no significant effect on their headache.²

Pharmacy care

Pharmacy teams are well positioned to deliver primary and secondary prevention of MOH.4 For instance, pharmacy staff can raise awareness of MOH, which seems low even among well-educated people. Researchers surveyed 485 undergraduates at Birmingham University, 197 of whom had healthcare training. Seventy-eight per cent of respondents took paracetamol. Most (85 per cent) used painkillers for headaches but only 38 per cent of the healthcare group and 14 per cent of the other respondents said they were aware of MOH as a side-effect of analgesics.⁶

Educating people about MOH can alter their behaviour: 80 per cent of those in the Birmingham study said that they would change their painkiller use after receiving information about MOH. Of these, 57 per cent said that they would reduce their use of painkillers, 24 per cent would consult a doctor for advice about treating headaches and 19 per cent would stop using their analgesic. Nevertheless, 27 per cent of the healthcare group and 16 per cent of the other students would not alter their behaviour.⁶

In another study, 76 per cent of patients no longer overused analgesics 1.5 years after receiving “simple information” and 42 per cent reverted to episodic headaches.³

Similarly, a study from Norway concluded that screening and brief intervention could help treat MOH. The authors noted that healthcare professionals may experience “challenges” persuading patients that their analgesic could cause headaches. Using MOH as a diagnosis “opened up a space for change”, the study said,
but could leave some patients feeling guilty.⁵

In addition, the Birmingham study suggested that pharmacists should consider using the term ‘painkiller-induced headache’ when counselling people about MOH: 43 per cent of the non-healthcare group and 37 per cent overall preferred this term. Twenty-seven per cent of the healthcare group preferred ‘painkiller-overuse headache’. Just 10 per cent preferred MOH.⁶

Watch for relapse

Withdrawing the overused medication usually improves MOH.³ Indeed, simple withdrawal and providing information and education can reduce MOH to episodic headaches in more than half of patients.2 Specialist services can help many other patients.

Pharmacists should warn patients that they might experience withdrawal symptoms, most commonly an initial worsening of the headache. The duration of withdrawal headaches depends on the drug: about four days for triptans, approximately seven days for ergotamine and about 10 days for simple analgesics. Some patients experience symptoms such as nausea, vomiting, sleep disturbances, anxiety, restlessness and nervousness.³

Pharmacists should be alert for relapses, which can range from a rate of 28-31 per cent within six months of withdrawal to 41 and 45 per cent at one and four years respectively. Relapse rates at four years in people with MOH from analgesics can reach 71 per cent. Several factors seem to increase the risk of relapse including:
• High initial intake of the overused analgesic
• Restarting previously overused drugs
• Failure to improve two months after stopping the drug
• Smoking and alcohol use.¹

Ensuring patients are using effective pain relief is arguably the most important role of any healthcare professional. It is therefore something of a tragic irony that MOH is so common, so disabling and so costly.

<sup>References
1. Headache 2013; 54:211-217
2. Headache 2014; 54:1251-7
3. Therapeutic Advances in Drug Safety 2014; 5:87-99
4. Headache 2014; 54:1019-1025
5. British Journal of General Practice 2014; 64:e525-e531
6. The Journal of Headache and Pain 2014; 15:10-10</sup>