MOH is a serious, disabling and well-characterized disorder, which represents a worldwide problem and is now considered the third-most prevalent type of headache.
However, it is estimated that MOH affects approximately 1-2% of the general population, but its relative frequency is much higher in secondary and tertiary care.
[5] MOH is known to occur with frequent use of many different medications, including most commonly: triptans,[6] ergotamines,[7] simple and combination analgesics,[8][9] and opioids.
[17] The underlying mechanisms that lead to the development of the condition are still widely unknown and clarification of their role is hampered by a lack of experimental research or suitable animal models.
Various pathophysiological abnormalities have been reported and they seem to have an important role in initiating and maintaining chronic headache (genetic disposition, receptor and enzyme physiology and regulation, psychological and behavioural factors, physical dependencies, recent functional imaging results).
[19] A PET study in patients with chronic analgesic overuse showed decreased activity in the orbitofrontal cortex of the brain, which is also seen in substance abuse.
Some effective preventive medications include Elavil (amitriptyline), Depakote (valproate), Topamax (topiramate), and Inderal (propranolol).
[25] However, the discontinuation of overused drugs may lead to the initial worsening of headaches, nausea, vomiting, sleep disturbance, anxiety, and restlessness.
[27][28] Two months after the completion of a medication withdrawal, patients with MOH typically notice a marked reduction in headache frequency and intensity.
Most physicians prefer inpatients programmes, however effective drug withdrawal may also be achieved in an outpatient setting in uncomplicated MOH patients (i.e. subjects without important co-morbidities, not overusing opioids or ergotaminics and who are at their first detoxification attempt).
[30] Following an initial improvement of headache with the return to an episodic pattern, a relevant proportion (up to 45%) of patients relapse, reverting to the overuse of symptomatic drugs.
[citation needed] MOH is clearly a cause of disability and, if not adequately treated, it represents a condition of risk of possible co-morbidities associated to the excessive intake of drugs that are not devoid of side-effect.
MOH can be treated through withdrawal of the overused drug(s) and by means of specific approaches that focus on the development of a close doctor-patient relationship in the post-withdrawal period.