8.2 Medication-overuse headache (MOH)

Previously used terms:
Rebound headache; drug-induced headache; medication-misuse headache.

Coded elsewhere:
Patients with a pre-existing primary headache who in association with medication overuse develop a new type of headache or a marked worsening of their pre-existing headache that, in either case, meets the criteria for 8.2 Medication-overuse headache (or one of its subtypes) should be given both this diagnosis and the diagnosis of the pre-existing headache. Patients who meet criteria for both 1.3 Chronic migraine and 8.2 Medication-overuse headache should be given both diagnoses.

Description:
Headache occurring on 15 or more days per month developing as a consequence of regular overuse of acute or symptomatic headache medication (on 10 or more or 15 or more days per month, depending on the medication) for more than three months. It usually, but not invariably, resolves after the overuse is stopped.

General comment:
In the criteria set out below for the various subtypes, the specified numbers of days of medication use considered to constitute overuse are based on expert opinion rather than on formal evidence.

Diagnostic criteria:
A. Headache occurring on ≥15 days per month in a patient with a pre-existing headache disorder
B. Regular overuse for >3 months of one or more drugs that can be taken for acute and/or symptomatic treatment of headache1
C. Not better accounted for by another ICHD-3 diagnosis.

Note:
1. Patients should be coded for one or more subtypes of 8.2 Medication-overuse headache according to the specific medication(s) overused and the criteria for each below. For example, a patient who fulfils the criteria for 8.2.2 Triptan-overuse headache and the criteria for one of the subforms of 8.2.3 Simple analgesic-overuse headache should receive both these codes. The exception occurs when patients overuse combination-analgesic medications, who are coded 8.2.5 Combination-analgesic-overuse headache and not according to each constituent of the combination-analgesic medication.

Patients who use multiple drugs for acute or symptomatic treatment of headache may do so in a manner that constitutes overuse even though no individual drug or class of drug is overused; such patients should be coded 8.2.6 Medication-overuse headache attributed to multiple drug classes not individually overused.

Patients who are clearly overusing multiple drugs for acute or symptomatic treatment of headache but cannot give an adequate account of their names and/or quantities are coded 8.2.7 Medication-overuse headache attributed to unverified overuse of multiple drug classes until better information is available. In almost all cases, this necessitates diary follow-up.

Comments:
8.2 Medication-overuse headache is an interaction between a therapeutic agent used excessively and a susceptible patient. Among those with a previous primary headache diagnosis, most have 1. Migraine or 2. Tension-type headache (or both); only a small minority have other primary headache diagnoses such as 3.3 Chronic cluster headache or 4.10 New daily persistent headache.

The diagnosis of 8.2 Medication-overuse headache is extremely important clinically. Approximately half of people with headache on 15 or more days per month for more than three months have 8.2 Medication-overuse headache. Evidence shows that the majority of patients with this disorder improve after discontinuation of the overused medication, as does their responsiveness to preventative treatment. Simple advice on the causes and consequences of 8.2 Medication-overuse headache is an essential part of its management. An explanatory brochure is often all that is necessary to prevent or discontinue medication overuse. Prevention is especially important in patients prone to frequent headache.

However, the behaviour of some patients with 8.2 Medication-overuse headache is similar to that seen with other drug addictions, and the Severity of Dependence Scale (SDS) score is a significant predictor of medication overuse among headache patients.