Definition and Overview
Medication overuse headache (MOH) is a chronic daily headache caused by regular overuse of acute headache medications. ICHD-3 criteria define MOH as headache occurring 15 or more days per month in a patient with a pre-existing headache disorder who regularly overuses acute medication for more than 3 months [1].
MOH affects approximately 1-2% of the general population and complicates about 50% of chronic daily headache cases. It is the third most common headache disorder globally [2].
Causative Medications and Thresholds
- Simple analgesics (acetaminophen, NSAIDs): 15 or more days per month
- Triptans: 10 or more days per month
- Opioids: 10 or more days per month
- Combination analgesics (containing caffeine, barbiturates): 10 or more days per month
- Multiple drug classes combined: 10 or more days per month total
Opioids and combination analgesics carry the highest risk and develop MOH fastest [3].
Pathophysiology
Central sensitization: repeated analgesic use leads to upregulation of pronociceptive pathways and downregulation of antinociceptive mechanisms. Trigeminal sensitization and reduced descending pain inhibition develop [4].
Serotonin receptor downregulation occurs with triptan overuse. Changes in cortical excitability and altered pain processing in the periaqueductal gray and thalamus are documented on functional imaging.
Diagnosis
ICHD-3 criteria for MOH [1]:
- Headache occurring on 15 or more days per month in a patient with pre-existing headache
- Regular overuse of acute headache medication for more than 3 months
- Not better accounted for by another ICHD-3 diagnosis
A detailed medication diary is essential. The diagnosis is confirmed when headache improves after medication withdrawal.
Treatment
Medication Withdrawal
Abrupt withdrawal is generally recommended for simple analgesics and triptans. Gradual tapering is preferred for opioids, barbiturates, and benzodiazepines to avoid withdrawal seizures [5].
Withdrawal symptoms (worsened headache, nausea, anxiety, insomnia) typically last 2-10 days for triptans and up to 2-4 weeks for opioids.
Bridge Therapy
Short courses of corticosteroids (prednisone), nerve blocks (greater occipital nerve block), or naproxen can ease the withdrawal period.
Preventive Therapy
Initiating or optimizing preventive medication (topiramate, amitriptyline, CGRP monoclonal antibodies) alongside withdrawal improves outcomes. CGRP antibodies show promise as they are effective even without prior medication withdrawal.
Prevention
Limit acute medication use to no more than 2-3 days per week. Keep a medication diary. Start preventive therapy when attack frequency exceeds 4 days per month. Patient education about MOH risk is essential at the time of acute medication prescription.