Fremanezumab: what it treats, how to use it, side effects
Last updated September 3, 2026.
Fremanezumab is a monoclonal antibody - it blocks CGRP, the natural substance that drives migraine attacks. You may know it as Ajovy. A self-injection that prevents migraines - with a choice in the rhythm: monthly or quarterly. This class is prescribed and trained by specialists - never by Pymander.
What does it treat?
Migraine prevention - fewer attacks per month, not relief of the attack in progress.
How do you use it?
Subcutaneous - under the skin - from a prefilled syringe or autoinjector, on one of two schedules: once a month as a single injection, or once every 3 months as 3 injections back to back - your prescriber sets the rhythm and you anchor the date. Training first: your doctor shows you or your caregiver the technique. The device warms out of the fridge on a flat surface for 30 minutes - never microwave, hot water, or sunlight. Each device is single-use, into a puncture-resistant sharps container. Missed dose: inject as soon as you remember, then reset the schedule from there per your prescriber.
Side effects to know
- Common: pain, swelling, or redness at the injection site.
- Serious - call your doctor immediately, and note these can arrive up to a month after the injection: hives; itching; flushing of the face; difficulty breathing; swelling of the face, mouth, tongue, or throat - and numb, cold, painful, or discolored fingers or toes.
Who should not use it?
Anyone with a past serious allergic reaction to it. Flag circulation problems and every other medication. Prevention, not rescue: an attack in progress still uses its own acute treatment. If you become pregnant, call your doctor.
When is it an emergency?
Trouble breathing or face or throat swelling is a 911 call - even weeks after the injection. For a dosing error, call Poison Control at 1-800-222-1222. Pymander's escalation routing is built and tested specifically for this class of decision; see the safety architecture working paper.
What a Pymander AI doctor consult looks like
Illustrative example, not a real member's messages.
Common questions
Monthly or quarterly - what is the difference?
Rhythm, not strength: the monthly schedule is one injection each month; the quarterly is 3 injections back to back every 3 months - same antibody, same total coverage. The choice is practical: fewer injection days vs. fewer pens per session. Your prescriber sets it, and switching between the rhythms is a simple decision at a visit, not a restart.
How does an injection prevent migraines?
Antibody logic: fremanezumab binds CGRP - the signal molecule that fires migraine attacks - and an antibody circulates for weeks. The injection keeps the signal blocked continuously. That is why the schedule anchor matters: late doses leave coverage gaps, and attacks read the gap.
Why does the device need 30 minutes out of the fridge?
Cold liquid under the skin hurts, and the device is designed for room-temperature dosing: 30 minutes on a flat surface, away from sunlight, cap on. Never speed it up - microwave, hot water, and sunlight all damage the antibody. Fridge to counter to injection: the whole choreography. Each device is single-use, straight into a sharps container.
What is the finger-and-toe warning?
Named for the class: fingers or toes turning numb, cold, painful, or discolored is a call-immediately item - and the label notes these reactions can arrive up to a month after the injection. Rare, specific, memorable. The site reactions - pain, redness, swelling at the injection spot - are the common, mild, expected kind.
Can I travel with it?
The fridge requirement shapes travel: the devices ride cold in a cooler pack, never frozen, never left in a hot car. Trips spanning an injection day take a plan with the pharmacy and prescriber in advance - including the missed-dose rules - rather than improvisation from a hotel room.
What happens if I miss an injection?
Inject as soon as you remember, then reset the schedule from the new date - confirm the reset with your prescriber. What a gap looks like: protection fades over the following weeks and the diary shows it. Tying the date to a fixed monthly or quarterly marker - the first, a birthday, a billing date - keeps the question rare.