Your First CGRP Injection: An Honest Guide to Aimovig, Ajovy, and Emgality at Home

The Click

The pen weighs almost nothing. You press it against your thigh, count to fifteen, and hear two clicks — one when the needle deploys, one when the dose finishes. The first preventive medication ever designed specifically for migraine has just entered your body, and the most dramatic part was unscrewing a plastic cap.

Then comes the strange part. You go on with your day. The migraines do not stop. A week passes. Two weeks. You start wondering if you injected something real or just played an expensive game of pretend.

This is the honest version of starting a CGRP monoclonal antibody. Aimovig, Ajovy, and Emgality reshaped migraine medicine in 2018 — but the brochures never explain what the first three months actually feel like, why some people get constipated and others do not, or why your neurologist suddenly cares about your blood pressure. Here is what 30 years of living with migraine and a careful read of the trial data have taught me about going in with eyes open.

What You Are Actually Injecting

CGRP stands for calcitonin gene-related peptide. It is a small protein your trigeminal nerves release during a migraine attack, widening blood vessels around your brain and carrying pain signals into the brainstem.^[1] Inject CGRP into a healthy volunteer and a migraine appears within hours.^[2] Block CGRP and the entire cascade stalls before it can build.

The three at-home injections do this in two different ways. Aimovig (erenumab) blocks the receptor — the lock the CGRP key fits into. Ajovy (fremanezumab) and Emgality (galcanezumab) bind the CGRP molecule itself, soaking up the key before it can find a lock.^[3] That mechanical difference matters more than the marketing suggests. It explains why one of the three quietly wrecks your digestion.

The Six-Week Question

Here is the data nobody quotes you out loud. In the STRIVE trial of episodic migraine, half the patients on 140 mg erenumab cut their monthly migraine days by 50% or more — compared with 26.6% on placebo.^[4] Galcanezumab in EVOLVE-1 reduced migraine days by roughly 1.9 more than placebo each month.^[5] Fremanezumab in HALO CM helped 39% of chronic migraine patients hit the 50% mark versus 18% on placebo.^[6] Real benefit. Not magic.

The bigger surprise is timing. About 60% of eventual responders show clear improvement by week 12. Of those who do not, roughly half will respond by week 24 — the late responders. A smaller group, the ultra-late responders, only improve after six months.^[7] A 24-month Japanese cohort watched response rates climb from 45.9% at month three to 71.0% at month 24.^[8]

The Constipation Conversation

The clinical trial paperwork lists constipation as an erenumab side effect at 1–4%. Real-world data tells a different story. A German cohort found 18.7% of patients constipated.^[9] A French registry: 15.7%.^[10] A 52-week Italian study: the most common adverse event of any kind.^[11] One switching study found 79% of patients on erenumab reported constipation before they changed drugs.^[12]

The other two are kinder to the gut. Fremanezumab and galcanezumab bind CGRP itself, not the receptor — and CGRP receptors line the walls of your intestines, where they keep food moving. Block the receptor and the bowels stall.^[13] When patients with severe erenumab-related constipation switched to fremanezumab, the rate collapsed from 79% to 12%.^[12] If you are starting Aimovig and your gut has always run sluggish, mention this before your first dose, not after your third.

How to Actually Inject

The medication lives in the fridge at 2–8°C (36–46°F). Thirty minutes before you inject, pull it out and let it warm to room temperature on the counter. Do not microwave it. Do not run it under hot water. Do not park it on the radiator.^[15] Cold injections sting more and may not deliver the full dose.

Pick a spot: front of the thigh, lower abdomen at least 5 cm from your navel, or the back of your upper arm if someone else is injecting you. Rotate sites each month so the same patch of skin does not stay angry. Clean with alcohol, let it dry, press the pen flat against the skin, push down firmly until the first click. Hold for 15 seconds (Aimovig) or until the second click signals the dose finished. Done.

The medication can stay at room temperature for up to 7 days, but cannot return to the fridge once removed.^[16] Plan around this when you travel.

What to Ask Before Your First Dose

Bring this list to your appointment:

• Which drug, and why this one for me? Receptor-blocker or ligand-blocker matters for side effects.
• What is my honest baseline? Track migraine days for 4 weeks before your first injection. Without that number, you cannot measure response.
• When do we decide it is working? European Headache Federation guidelines recommend at least 3 months before judging.^[17]
• Pregnancy planning? All three drugs have long half-lives and should be stopped 5–6 months before trying to conceive.^[18]
• Cardiovascular history? CGRP helps regulate blood pressure. Patients with stroke, coronary disease, or uncontrolled hypertension were excluded from every trial.^[19]
• What happens when I stop? A multicenter study found migraines often drift back toward baseline within 1–3 months of discontinuation, though some patients hold their gains.^[20]

What These Drugs Are Not

CGRP injections prevent migraines. They do not abort one already underway — that is the job of triptans, gepants, or ditans. They do not cure migraine. They cut frequency and severity for roughly half of episodic patients and a third of chronic patients.^[21] The other half will try a second CGRP, layer in Botox, add a daily gepant, or revisit older preventives. None of this is failure. This is medicine.

The honest framing: these are the first migraine drugs ever designed for migraine, not borrowed from epilepsy, depression, or heart disease. Adherence at 12 months runs around 55% on CGRP mAbs versus 35% on older oral preventives^[22] — not because the drug is perfect, but because the trade-offs are finally tilted in our favor. That alone is new.