Migraine - BTX or Anti-CGRPs?

Both Anti-CGRP (Calcitonin Gene-related Peptide Mononoclonal Antibodies) and BTX are used for the prevention of Migraine. These treatments are usually not first line treatments. Due to the higher cost of these treatment, these medications are prescribed when there is intolerance or insufficient response to other preventive medications. The aims of these medications are to reduce the number of headache days and severity of headaches. You may have been offered these specialized treatments by your Pain Specialist. This article was written to help you understand these two treatment modalities better.

BTX
BTX is a medication made from a toxin produced by the bacteria Clostridium Botulinum. When injected, BTX goes into the cells and cuts a protein called the SNARE complex. This cutting stops the release of certain chemicals called neuropeptides. It's believed that by reducing these neuropeptides, BTX helps to ease migraines. So, basically, BTX works by blocking certain signals in the brain that can trigger migraines, helping to reduce their frequency and severity.

The discovery of BTX for migraine treatment began with anecdotal reports from patients with migraine who underwent BTX injections for aesthetic reasons in the late 1990s. Formal clinical trials in the early 2000s substantiated its efficacy. In 2010, the FDA approved BTX for chronic migraine treatment, defined as experiencing headaches on 15 or more days per month. This approval was based on studies which demonstrated that BTX, when injected in specific parts of the face, neck and head), substantially reduced migraine frequency and severity. 

This treatment involves injection over several parts of the head and neck using a very fine needle every 3 to 4 months. It is generally well-tolerated with very few side effects. However, in some instances, the injection can lead to muscle weakness (eg. drooping of the eyelids). These instances are generally uncommon and resolve without treatment. Patients who have Myasthenia Gravis should avoid this treatment.

Anti-CGRPs
CGRP molecules play a crucial role in migraine pathophysiology, contributing to blood vessel dilation and pain sensation associated with migraines. Elevated levels of circulating CGRP during migraine attacks prompted the development of monoclonal antibodies targeting CGRP or its receptors. These anti-CGRP monoclonal antibodies work by reducing circulating CGRP levels. Research has demonstrated a decrease in migraine frequency with anti-CGRP injections. Since 2018, the FDA has approved several anti-CGRP treatments for migraine management.

This treatment involves injection into the fat using a very fine needle on a monthly basis. It can be self-administered and is generally well tolerated with very few side effects. The most common side effect encountered is constipation and redness over the injection site. 

Aimovig (Erenumab) is a once-a-month injection that is indicated for chronic migraines. It can be self-administered by patients.

Choosing between BTX & Anti-CGRPs
As of the time of the publication of this article, we know of no head-to-head comparison of these two treatments. Nevertheless, non-comparative studies show that these two treatments have fairly similar levels of effectiveness. In addition, studies show that BTX and Anti-CGRPs have synergistic effects. This means that patients who have combination treatment tend to have better outcomes than patients who are treated only with Anti-CGRPs.

In conclusion, both Anti-CGRP (Calcitonin Gene-related Peptide Monoclonal Antibodies) and BTX (Onabotulinum Toxin A) are utilized for migraine prevention, typically when other preventive medications have not provided sufficient relief. These treatments aim to reduce the number of headache days and severity of headaches. BTX works by blocking certain brain signals through the inhibition of neuropeptide release, while Anti-CGRP antibodies target CGRP, a key molecule in migraine pathophysiology. While both treatments have demonstrated effectiveness in reducing migraine frequency and severity, they are often reserved for patients with intolerances or inadequate responses to other therapies due to their higher cost. Patients considering these specialized treatments should consult with their Headache Pain Specialist to determine the most suitable option based on individual needs and treatment goals.

Other pages of interest:
1. BTX (Chronic Migraine) Information sheet 
2. Aimovig (Erenumb) Information sheet

​Dr. Christopher Liu is a Singapore-based Headache & Pain Specialist with over a decade of experience in treating Headaches & Orofacial Pain. Visit www.drchristopherliu.com to find out more.