You give yourself the first injection and mark the date. Your neurologist said three months. You track carefully: 18 migraines in month one, 17 in month two, 16 in month three. The numbers aren't really different.
The advice is to give it six months. Some patients take longer. Month six looks the same.
For roughly half of patients in the clinical trials, this is exactly what Aimovig looks like. Not because the drug failed, because CGRP wasn't the dominant driver. That distinction matters for what to investigate next.
Why this matters
CGRP antibodies provide the most sustained CGRP suppression available, 24/7 for a full month. If that level of CGRP blockade doesn't resolve your migraines, CGRP is almost certainly not your dominant driver. That narrows the search significantly.
Why standard answers miss the point
The standard next step after Aimovig fails is to switch to a molecule blocker (Ajovy or Emgality) or try a gepant like Nurtec.
That can occasionally help, the mechanisms differ enough that a switch produces a response in some patients. But if your migraines aren't primarily CGRP-driven, switching within the CGRP class is unlikely to change much. The more useful question is: what mechanism is actually running your attacks? Histamine, hormonal instability, and vascular dynamics are the most common drivers that CGRP blockade doesn't reach.
Mechanism
How CGRP antibodies work (and how they differ)
All three CGRP antibodies are monoclonal antibodies, large engineered proteins injected monthly (or quarterly for Ajovy) that provide continuous CGRP suppression. But they work through two different approaches:
Receptor blocker
Aimovig (erenumab)
Blocks the CGRP receptor itself, preventing CGRP from binding to it. Like putting a lock on a door: CGRP is still circulating, but it can't activate its target receptor.
Molecule blockers
Ajovy (fremanezumab) and Emgality (galcanezumab)
Bind to the CGRP molecule itself, neutralizing it before it can reach any receptor. Like intercepting a messenger before they deliver the message.
This distinction matters for one practical reason: some patients who don't respond to the receptor blocker (Aimovig) do respond to a molecule blocker (Ajovy or Emgality), and vice versa. The mechanisms overlap but aren't identical. If one CGRP antibody fails, switching to the other type may be worth discussing before concluding the entire class doesn't work for you.
Why they fail
Why CGRP antibodies don't work for everyone
CGRP isn't your dominant driver
CGRP is involved in most migraines, but "involved" doesn't mean "dominant." If your migraines are primarily driven by histamine pathways, autonomic dysfunction, hormonal instability, or vascular underfill, blocking CGRP removes a minor player while the main drivers continue unchecked.
The clinical trials showed about 50% of chronic migraine patients achieved a meaningful reduction (50%+ fewer migraine days). That means for roughly half of patients, even sustained, continuous CGRP blockade wasn't enough, because CGRP wasn't the main story.
The migraine has centralized
CGRP antibodies are large molecules that don't easily cross the blood-brain barrier. They primarily work on peripheral CGRP signaling, in the trigeminal ganglion and meningeal blood vessels. In chronic migraine that has become centrally sensitized, where the brainstem and cortex have become independently reactive, peripheral CGRP blockade may not reach the pain processing centers that are now driving the attacks.
This may explain why CGRP antibodies tend to work better for episodic migraine than for long-standing chronic migraine with significant central sensitization.
Side effects create new problems
CGRP has functions beyond migraine. It helps regulate gut motility, blood vessel tone, and wound healing. Blocking it can produce:
- Constipation (especially with Aimovig), sometimes severe enough to require intervention
- Muscle cramps and spasms, CGRP helps regulate vascular tone in muscle tissue
- Hypertension, CGRP is a vasodilator, so blocking it can raise blood pressure in some people
- Worsening Raynaud's symptoms, reduced vasodilation in extremities
In some cases, these side effects create enough systemic stress or autonomic disruption to partially offset the migraine benefit.
The pattern shifted
If a CGRP antibody worked initially and then lost effectiveness, your migraine pattern likely changed. Perimenopause, new medications, increased histamine sensitivity, worsened sleep, or new stressors can shift the dominant driver away from CGRP. The drug is still blocking CGRP just as effectively, but CGRP is no longer the main issue.
Class comparison
CGRP antibodies vs gepants: what failure of one tells you about the other
If Aimovig (or Ajovy/Emgality) didn't work, you might wonder whether Nurtec or Ubrelvy (gepants) would be different. They target the same pathway but work differently:
CGRP antibodies
Provide constant, sustained blockade for 4 weeks. They're large molecules that work peripherally.
Gepants
Nurtec and Ubrelvy are small molecules that provide shorter, intermittent blockade. They cross the blood-brain barrier more readily, potentially reaching central CGRP pathways.
Because of these differences, some patients who fail CGRP antibodies still respond to gepants (and vice versa). If you failed Aimovig but haven't tried Nurtec, it may still be worth discussing. However, if you've tried both a CGRP antibody and a gepant with no meaningful response, CGRP blockade as a strategy has been thoroughly tested, the driver is almost certainly elsewhere.
Diagnosis by exclusion
The more CGRP approaches you've tried without success, the stronger the signal: your migraines are not primarily CGRP-driven. That's not a failure, it's a diagnosis by exclusion that points the investigation toward histamine, vascular, hormonal, or autonomic pathways.
Pattern recognition
Does this pattern fit you?
Worth testing
- - You've completed 3+ months of a CGRP antibody with minimal improvement
- - Aimovig helped initially but gradually lost effectiveness
- - Nurtec also didn't work (suggesting CGRP isn't your driver)
- - Your migraines come with congestion, flushing, or food-related patterns (suggesting histamine)
- - Migraines are clearly tied to hormonal timing, posture, or hydration
- - You developed significant constipation or muscle cramps on Aimovig
- - Multiple medication classes have failed and you've been labeled treatment-resistant
Probably not the priority
- - You've only completed 1-2 injections (give it the full 3-month trial first)
- - You had a clear partial response (50%+ reduction) and side effects are tolerable
- - Side effects are the dominant issue rather than lack of efficacy
- - You haven't tried a different mechanism class (Aimovig only) and switching wasn't discussed
Next steps
What to discuss with your clinician
Conversation starters
- •Whether switching between receptor blocker (Aimovig) and molecule blocker (Ajovy/Emgality) is worth trying before abandoning the class
- •Whether trying a gepant (Nurtec, Ubrelvy) could reach central CGRP pathways the antibodies missed
- •Whether investigating histamine, hormonal, vascular, or autonomic pathways could identify the actual driver
- •Whether the pattern of what has and hasn't worked narrows down the likely migraine mechanism
- •Whether combining a CGRP approach with treatment of other layers (sleep, sodium, hormonal stability) could improve the overall outcome
Reframe
The part most people miss
Failure as signal
CGRP antibodies are the most targeted migraine treatment ever developed. When they don't work, it's not a failure of modern medicine, it's the clearest possible signal that your migraines live somewhere else in the system.
Each medication failure narrows the search. Triptans failed? Serotonin pathways aren't the answer. Topamax failed? Neural excitability isn't the primary driver. CGRP antibodies failed? CGRP isn't running the show. Botox failed? Peripheral nerve signaling isn't the main input. What's left? Histamine, vascular dynamics, hormones, autonomic regulation. The pattern of failures is itself a diagnostic tool.
This guide is for education and pattern-recognition only. It is not medical advice and is not a plan to start, stop, or change any medication, supplement, or test. Always discuss treatment decisions with a licensed clinician who knows your history.
Clinical and review articles
- Goadsby PJ et al. A controlled trial of erenumab for episodic migraine. New England Journal of Medicine. 2017;377(22):2123-2132.
- Silberstein SD et al. Fremanezumab for the preventive treatment of chronic migraine. New England Journal of Medicine. 2017;377(22):2113-2122.
- Stauffer VL et al. Evaluation of galcanezumab for the prevention of episodic migraine: the EVOLVE-1 randomized clinical trial. JAMA Neurology. 2018;75(9):1080-1088.
- Edvinsson L. The trigeminovascular pathway: role of CGRP and CGRP receptors in migraine. Headache. 2017;57(S2):47-55.
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Frequently asked questions
- Why is Aimovig not working for my migraines?
- Aimovig blocks the CGRP receptor, preventing CGRP from triggering vasodilation and pain signaling. If your migraines are primarily driven by histamine, vascular instability, hormonal shifts, or autonomic dysfunction, blocking CGRP won't address the main driver. About 50% of patients don't achieve a meaningful response to CGRP antibodies, suggesting CGRP isn't the dominant pathway for a large portion of migraine sufferers.
- How long should I try Aimovig before deciding it doesn't work?
- Most headache specialists recommend at least 3 monthly injections (3 months) before concluding a CGRP antibody isn't effective. Some patients respond as late as the 6th injection. However, if you experience significant side effects (severe constipation, muscle cramps, or worsening migraines), discuss with your clinician whether continuing is appropriate.
- What is the difference between Aimovig, Ajovy, and Emgality?
- Aimovig (erenumab) blocks the CGRP receptor. Ajovy (fremanezumab) and Emgality (galcanezumab) block the CGRP molecule itself before it reaches the receptor. This distinction matters because some patients respond to one approach but not the other - receptor blockade vs molecule capture can produce different results depending on how your CGRP system functions.
- Should I switch to a different CGRP antibody if one doesn't work?
- It's worth discussing with your clinician. Since Aimovig blocks the receptor while Ajovy and Emgality block the molecule, switching between these approaches can occasionally produce a response when the first didn't work. However, if the fundamental issue is that CGRP isn't your primary migraine driver, switching within the same drug class is unlikely to help.
- Can Aimovig cause constipation?
- Yes. CGRP plays a role in gut motility, and blocking it can slow intestinal movement. Constipation is one of the most common side effects of Aimovig specifically (because it blocks the receptor rather than the molecule). For some people, severe constipation becomes its own quality-of-life issue, and in rare cases it can worsen migraines indirectly through autonomic and inflammatory effects.
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Related reading
This is educational content, not medical advice. Always consult a qualified clinician.