HEADACHE DUE TO CHRONIC MEDICATION USE: CLINICAL MANIFESTATIONS, DIAGNOSIS, AND MANAGEMENT

Abstract

Medication overuse headache (MEH), also known as medication-overuse headache, is a nosological entity classified as a secondary headache in the International Classification of Headache Disorders (ICHD-3). It is a highly prevalent condition in neurological practice, with a significant impact on functionality, quality of life, and healthcare costs, and is frequently underdiagnosed and inadequately managed. This condition results from the regular, frequent, and prolonged use of symptomatic drugs for pain relief, including simple analgesics, nonsteroidal anti-inflammatory drugs, triptans, ergotamines, opioids, and combinations containing caffeine. Overuse is generally defined as the use of these medications for more than 10 to 15 days per month, for a period exceeding three months, depending on the pharmacological class. Paradoxically, these drugs, initially used to control headaches, begin to act as a perpetuating factor for pain, promoting its chronicity. From a clinical standpoint, chronic headache syndrome (CHS) is characterized by headaches occurring 15 or more days per month, frequently with a daily or near-daily pattern, variable intensity, and mixed phenotypic characteristics, potentially mimicking or overlapping aspects of tension-type headache and migraine. It typically affects individuals with a history of primary headache, especially migraine, in whom a transformation to a chronic pattern occurs. Associated symptoms such as nausea, photophobia, phonophobia, sleep disturbances, irritability, and cognitive impairment are common, frequently associated with psychiatric comorbidities such as anxiety disorders and depression. The pathophysiology involves complex and not yet fully elucidated mechanisms, including central sensitization, dysfunction of descending pain modulation systems, alterations in serotonergic and dopaminergic systems, as well as behavioral components related to drug dependence. These alterations contribute to a reduction in the nociceptive threshold and maintenance of the chronic pain cycle. Given this scenario, early recognition of chronic headache overuse (CHW) is fundamental and is based on a detailed medical history, with emphasis on the pattern of medication use, and the application of established diagnostic criteria. Therapeutic management requires a structured and multidisciplinary approach, centered on discontinuing the causative agent, introducing prophylactic therapies for the underlying primary headache, and non-pharmacological interventions such as cognitive-behavioral therapy. Patient education and rationalization of medication use are essential pillars for relapse prevention and optimization of clinical outcomes.