BACKGROUND: Previous studies found low serum levels of nociceptin in migraine patients but high serum levels of calcitonin gene-related peptide (CGRP). CGRP can elicit migraine-like headache. Medication-Overuse Headache (MOH) often has migraine features and can mimic chronic migraine. We therefore hypothesized that as in migraine, serum levels of nociceptin would be lower and CGRP serum levels higher in MOH patients compared with those in healthy volunteers. We hypothesized that the serum levels would normalize after detoxification.

METHODS: Seventeen MOH patients, hereof 70.6% with chronic migraine and MOH, and 30 sex and age matched headache-free controls were included. MOH patients underwent a 2-month outpatient detoxification program and after 6 months, 10 patients and 19 controls were retested. Blood samples were analyzed blinded.

RESULTS: We found no differences in the levels of nociceptin and CGRP between MOH patients and controls (P = 0.65 and P = 0.59). The mean headache frequency reduction was 43% and 70% of patients reverted to episodic headache after 6 months, but the levels of nociceptin and CGRP were unchanged (P = 0.71 and P = 0.82).

CONCLUSION: In contrast to previous findings in migraine patients, we found normal serum levels of nociceptin and CGRP in MOH patients. Thus, we find no evidence that the increased headache frequency of MOH patients could be caused by altered nociceptin and CGRP levels. This underlines the importance of identifying medication overuse in chronic headache and treating the MOH.