Exploring medication-overuse and medication-overuse headache in cluster headache.

BackgroundIt is not well established to what extent medication-overuse occurs in cluster headache (CH), if medication-overuse headache exists in CH and whether the existing criteria for medication-overuse headache are a suitable diagnostic tool in CH. We aimed to examine the prevalence of medication-overuse and probable medication-overuse headache in a well characterized cohort of people with CH and describe associated factors and clinical impact.MethodsParticipants diagnosed with CH according to International Classification of Headache Disorders, 3rd edition (ICHD-3) beta and ICHD-3 were invited to participate in a semi-structured interview investigating medication-overuse and probable medication-overuse headache according to ICHD-3. To add nuance to the debate, we also included a more conservative definition, applying the ICHD-3 criteria for the medication-overuse but specified the headache phenotype to a daily bilateral headache.ResultsIn total, 21% of 433 participants with CH had a medication-overuse according to ICHD-3. Of these, 16% fulfilled the criteria for probable medication-overuse headache according to the ICHD-3, and 12% if excluding isolated triptan overuse. The overused analgesics constituted simple analgesics (52.2%), triptans (37.3%), opioids (29.9%) and combination therapies (20.9%). Associated factors were having chronic CH (odds ratio = 11.4,  < 0.00001) and comorbid migraine (odds ratio = 2.35,  < 0.05). Participants with probable medication-overuse headache had longer attack duration (30.0 vs. 20.0 minutes,  < 0.01) and less effect of acute and preventive medication than those without (20.0 vs. 55.9%,  < 0.05 and 13.3 vs. 37.3%,  < 0.01, respectively). If applying the conservative definition with a daily bilateral headache along with a medication-overuse, the prevalence was reduced to 4%.ConclusionsProbable medication-overuse headache was present in every sixth participant with CH in this large cross-sectional cohort study. Interestingly, only a smaller proportion was the result of isolated triptan overuse. In CH, where patients often suffer from daily attacks and may suffer from a daily bilateral inter-ictal pain, our very conservative definition noted a prevalence of 4%. While the existing ICHD-3 criteria for medication-overuse headache may not be directly applicable in CH, the applicability and validity of the very conservative definition warrant further investigation. Still, as in other cross-sectional populations with medication-overuse, we noted an association that acute and preventive treatments were less effective in participants with probable medication-overuse headache compared to those without. Altogether, future prospective studies are necessary to establish the exact extent and presentation of medication-overuse headache in CH and determine whether it is an aggravating factor for the disease. We do not recommend discontinuing triptans if suspecting MOH due to ethical concerns.