Long term headache duration is a factor predicting nonresponse to detoxification and advice in medication overuse headache.

Medication overuse headache (MOH) is a very heterogeneous disorder for which a recommended treatment is not yet available. The purpose of this study was to investigate any possible roles of demographic and clinical characteristics of MOH patients that might predict a response to detoxification and advice with or without preventive treatment.

This ancillary study is part of the Sodium vAlproate in the treatment of Medication Overuse HeadAche (SAMOHA) study that randomized 88 MOH patients for 3-month treatment period with sodium valproate (VPA) (800 mg/day) or placebo after a 6-day outpatient detoxification regimen. Demographic and clinical characteristics obtained on patients from both study arms were analyzed to point out an association with the response to the treatment. While for patients from VPA arm no significant results were obtained, comparing responders to non-responders to detoxification and advice to withdraw from MOH, a significant difference in headache duration was observed. Specifically, the efficacy of such treatment resulted ineffective in headache lasting longer than 30 years.

Our findings suggest that the benefit from detoxification and advice can be excluded in MOH of long duration. Therefore, a preventive treatment is suggested particularly for these patients.