An Exploratory Study of Salivary Calcitonin Gene‐Related Peptide Levels Relative to Acute Interventions and Preventative Treatment With Onabotulinumtoxin A in Chronic Migraine

Objective To determine if baseline/interictal saliva calcitonin gene‐related peptide ( CGRP ) levels would be lower in subjects with chronic migraine receiving onabotulinumtoxin A compared with those receiving saline. Background CGRP is considered central to the pathogenesis of episodic migraine, but its relationship to chronic migraine is less understood. Onabotulinumtoxin A is an effective treatment for chronic migraine and has been demonstrated to inhibit the vesicular release of CGRP . Methods This was an exploratory, randomized, placebo‐controlled, crossover pilot study of 20 subjects that received onabotulinumtoxin A and saline injection (placebo). The amount of CGRP in saliva samples collected on a nonheadache or low headache day, and prior to and after treatment of a headache exacerbation was measured. Daily headache records, medications, and response to treatment were recorded in a diary. Results A decrease in baseline/interictal saliva CGRP levels for subjects receiving onabotulinumtoxin A from 39.4 ± 7.5 pg CGRP /mg total protein after the first month to 25.5 ± 4.1 pg after the third month was observed. However, this difference did not reach significance nor was it significant when compared to the saline treatment. There was a reduction in the number of headache days for both onabotulinumtoxin A and saline over baseline throughout the active phases of the study. However, there was no statistical difference in headache days between groups. Subjects with a greater than 50% response to onabotulinumtoxin A had better 2‐hour pain relief with acute treatment than non‐responders to onabotulinumtoxin A or saline. Conclusion While CGRP levels were not elevated during a migraine attack in chronic migraine subjects as has been reported in episodic migraine, there was an overall decrease in the baseline/interictal levels in response to onabotulinumtoxin A .