Erenumab (Aimovig) was the first drug in the family of monoclonal antibodies (mAbs) against calcitonin gene-related peptide (CGRP) approved for the prevention of migraine headaches. CGRP is a substance released during a migraine attack. Erenumab was approved in May of this year, followed by approvals of fremanezumab (Ajovy) and galcanezumab (Emgality) in September. Erenumab is an antibody against the CGRP receptor located on a cell, while the other two drugs are antibodies against the molecule of CGRP. They have very similar efficacy and are surprisingly safe with very few side effects. Erenumab has no contraindications or drug interactions.
All these drugs are delivered by an injection and can cause a local injection site reaction or a rash, but erenumab can also cause constipation. It is possible that with the wider use of these drugs other side effects may become apparent. We have seen a handful of patients whose headaches worsened, a couple who developed fatigue and muscle aches, stomach pains and thinning of hair. The number of such patients is small and it is premature to attribute these effects to the drug. Just like our colleagues across the country, we at the New York Headache Center encourage our patients to report all potential side effects to the manufacturer or the FDA.
Erenumab dose is either a single 70 mg injection or two injections for a total of 140 mg. It comes in a prefilled pen-like device which is very easy to self-administer. It provides dramatic relief to about one in five patients and its overall efficacy is about 50% improvement in 50% of patients. About 30% obtain no relief. We do recommend at least two sets of monthly injections before giving up on erenumab.
Unlike Botox, which is approved for the prevention of only chronic migraines (15 or more headache days each month), erenumab is approved for migraines of any frequency. Usually, we consider preventive therapy in patients who have about 4 migraine attacks a month. Many insurance companies require a trial of two oral preventive drugs (which are extremely cheap) before they agree to pay for erenumab. The cost of erenumab is $575 a month, but the manufacturer offers a free trial and free treatment for up to a year if the insurer refuses to pay for it (you do need to get a denial of payment as well as a second denial upon appeal). The one-year free offer is not available to those on Medicaid or Medicare.
Erenumab and the other two CGRP mAbs are truly breakthrough medications which are changing lives of thousands of migraine sufferers. We are cautiously optimistic that their safety profile will remain as good as it appears to be now.
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