Emgality and Aimovig are not the same medication. They contain different active ingredients, are made by different manufacturers, and work through distinct biological mechanisms. However, they belong to the same drug class and serve a similar purpose: preventing migraine attacks by blocking a protein called CGRP (calcitonin gene-related peptide), which plays a central role in triggering migraine pain.
Both are self-injected once a month, both are prescribed for chronic and episodic migraine in adults, and both became available within months of each other in 2018. The similarities end there. The differences in how they target CGRP, their dosing, side effects, and approved uses can matter when choosing between them.
How They Block Migraine Pain Differently
CGRP is a signaling molecule that surges during migraine attacks, dilating blood vessels and amplifying pain signals. Aimovig (erenumab) and Emgality (galcanezumab) both interrupt this process, but they do it from opposite directions.
Aimovig blocks the CGRP receptor, the docking site where the molecule attaches to trigger pain signaling. Think of it as putting a lock on the door so CGRP can’t get in. It’s the only migraine prevention drug that works this way.
Emgality takes the other approach: it binds directly to the CGRP molecule itself, neutralizing it before it ever reaches the receptor. Two other migraine drugs (fremanezumab and eptinezumab) also target the molecule rather than the receptor. Whether one strategy is more effective than the other remains debated. Some researchers argue that blocking the receptor alone may be insufficient because CGRP can still act through alternative pathways, while others point to Aimovig’s longer track record of safety data spanning five years.
Dosing and the First Month
One of the most practical differences shows up right away. Emgality starts with a loading dose of 240 mg, which means two injections of 120 mg given back to back on your first day. After that, you take a single 120 mg injection once a month. The loading dose is designed to build up therapeutic levels of the drug faster, so some people notice benefit sooner.
Aimovig has no loading dose. You start at 70 mg once monthly, and your doctor may increase to 140 mg monthly if the lower dose isn’t providing enough relief. Both the 70 mg and 140 mg strengths come in a single prefilled autoinjector or syringe, so you never need more than one injection per visit at either dose.
Approved Uses
Both drugs are FDA-approved for migraine prevention in adults. Emgality has one additional approval that Aimovig does not: the treatment of episodic cluster headache. Cluster headaches are a different condition entirely, producing severe, one-sided pain around the eye that strikes in recurring bouts lasting weeks or months. For cluster headache, Emgality is dosed at 300 mg (three injections of 100 mg each) at the start of a cluster period, then monthly until the cluster period ends. If you experience cluster headaches rather than migraines, Emgality is currently the only CGRP-targeting drug approved for that purpose.
Side Effects Worth Knowing
Both medications are generally well tolerated, and their most common side effects overlap: injection site reactions like redness, pain, or itching where the shot is given. But each drug carries a few distinct concerns.
Aimovig has a notable association with constipation. In clinical trials, the 140 mg dose caused constipation in about 3% of patients compared to 1% on placebo. The 70 mg dose didn’t show a meaningful difference from placebo. For most people this is mild, but if you already deal with chronic constipation, it’s worth discussing with your prescriber.
Aimovig also carries an FDA-listed warning about blood pressure changes. Post-marketing reports have documented new-onset hypertension and worsening of existing hypertension, sometimes within seven days of a dose and most commonly after the very first injection. Some cases required medication or hospitalization. Patients on Aimovig should have their blood pressure monitored, especially early in treatment. Emgality’s labeling does not include a similar hypertension warning.
Latex Allergy Considerations
If you have a latex sensitivity, this is an important distinction. The needle shield on Aimovig’s prefilled autoinjector and prefilled syringe contains dry natural rubber, a latex derivative. The FDA labeling specifically warns individuals with latex allergies to inform their healthcare provider before using Aimovig. Emgality’s prefilled pen and syringe do not carry this same latex-related warning, making it the more straightforward choice for latex-sensitive patients.
Storage and Convenience
Both drugs are stored in the refrigerator and injected at home. If you need to travel or keep the medication out of the fridge, Aimovig can sit at room temperature for up to 7 days before it must be discarded. Emgality is similarly designed for home use and can be left at room temperature for a limited window, though the exact duration differs slightly by formulation. In practice, both are designed to fit into a monthly self-injection routine with minimal disruption.
Choosing Between Them
There is no universal “better” option between these two drugs. Clinical trials show both reduce monthly migraine days significantly compared to placebo, and no large head-to-head trial has declared a winner. The choice often comes down to practical factors: whether you want a loading dose for potentially faster onset (Emgality), whether you prefer starting at a lower dose with the option to increase (Aimovig), whether you have cluster headaches (Emgality is the only approved option), whether constipation or blood pressure concerns are relevant to your health history (tilting away from Aimovig), or whether a latex allergy rules out one device.
Insurance coverage and cost also play a significant role. Both manufacturers offer savings programs, but formulary placement varies widely between insurance plans. Some plans cover one but not the other, or require you to try one before approving the alternative. Checking your specific coverage before committing can save considerable time and frustration.
If one medication doesn’t work well enough after three to six months, switching to the other is common and reasonable. Because they target different parts of the CGRP pathway, a poor response to one doesn’t necessarily predict failure with the other.