Switching Calcitonin Gene–Related Peptide Inhibitors for Migraine Prophylaxis

Key Message

There are several different formulations of drugs that target calcitonin gene–related peptide (CGRP) available in Canada for preventing migraine. This Rapid Review examines the evidence regarding the effectiveness of different CGRP inhibitors after failure on a first or second CGRP inhibitor due to lack of efficacy or tolerability.

The review includes 1 systematic review of 7 nonrandomized studies, 3 additional nonrandomized studies, and 2 clinical guidelines, all published since 2020. The included studies all examined changes in monthly migraine days after switching to a new CGRP inhibitor. No economic studies were identified.

The findings generally show that patients experience improvement with the second CGRP inhibitor based on reported migraine events. However, the guidelines found there was not enough evidence to consider this practice evidence-based.

All the studies, including the clinical guidelines, were conducted in other countries, so it is not clear how applicable they are to patients in Canada.

All studies had very significant methodological concerns and their results should not be considered conclusive. In particular, all the primary studies were uncontrolled, meaning that bias from regression to the mean could not be ruled out.

Overall, the included studies do not offer clear guidance on the effectiveness of prophylactic CGRP inhibitors in patients with migraine who have failed treatment on a different CGRP inhibitor.