An anti-CGRP injection to prevent migraine
Fremanezumab
An under-the-skin injection given monthly or every three months to prevent migraine attacks.
What is Fremanezumab?
Fremanezumab (brand name Ajovy) is a newer type of medicine, called an anti-CGRP biologic, used to prevent migraine in people who have frequent attacks. It is given as an injection under the skin, either monthly or every three months, and it is taken regularly to reduce how often migraines happen — it is not a treatment for an attack that has already started. It works by blocking CGRP, a natural body chemical involved in migraine. It is generally well tolerated, with the most common problem being a reaction where the injection is given. It is usually offered only after older preventer medicines have not worked or were not suitable, and it is not recommended in pregnancy without specialist advice.
Education and reference only. This is a plain-language guide to Fremanezumab — it deliberately contains no doses. Doses depend on the person, the brand and the reason for treatment, and belong with your prescriber. Always check the BNF, the product labelling (SmPC) and follow medical advice.
What it is
Fremanezumab is a laboratory-made antibody, known as a biologic, that targets a body chemical called CGRP (calcitonin gene-related peptide), which plays a key part in migraine attacks. It is used as a preventer: taken regularly to reduce how often migraines happen, rather than to stop an attack that is already underway. In the UK it is usually considered for people with frequent or chronic migraine who have already tried at least three older preventer medicines without success. It is given as an injection under the skin, which people can often be taught to do at home.
How it works
During a migraine, levels of CGRP rise and help drive the pain and other symptoms. Fremanezumab attaches to CGRP itself and stops it acting, which over time reduces how often migraines occur and how severe they are. Because it is a preventer, it is taken on a regular schedule — monthly or every three months — and its benefit builds up gradually rather than working within minutes like a painkiller. It does not relieve an attack that has already begun, so a separate acute treatment is still needed for breakthrough migraines.
Company & origin
Originated / developed by: Teva.
A newer biologic medicine used in the UK to help prevent migraine in people who have frequent attacks and have already tried older preventers.
What it treats
Conditions Fremanezumab is used for
Practical use
How to take Fremanezumab
General, dose-free guidance — always follow your prescriber's and the leaflet's specific instructions.
- It is given as an injection under the skin, either once a month or as a larger dose every three months, depending on the schedule chosen with your specialist.
- Many people are taught to give the injection themselves at home into the stomach, thigh or upper arm, rotating the site each time.
- Take it regularly to prevent migraine; it will not relieve an attack that has already started, so keep using your usual acute migraine treatment as well.
- Allow a few months to judge whether it is working, as the benefit builds up gradually.
- Tell your specialist if you are pregnant, planning a pregnancy or breastfeeding, as it should only be used on specialist advice.
Weighing it up
Advantages & disadvantages of Fremanezumab
Advantages
- Can be given monthly or just once every three months, which suits people who prefer fewer injections.
- Generally well tolerated, with far fewer of the body-wide side effects seen with some older preventer tablets.
- Offers a newer option for people whose migraines have not responded to older preventer medicines.
Disadvantages
- It is a preventer only and does not treat an attack that has already begun.
- It is given by injection rather than as a tablet, and commonly causes injection-site reactions.
- It is usually only available after several older preventers have been tried, and its benefit takes some weeks to build.
Practical use
Good to know
It helps to understand the difference between preventers and acute treatments: fremanezumab is a preventer, taken regularly to make migraines less frequent, while you still need a separate medicine to treat an attack when one happens. The anti-CGRP medicines are a newer class developed for people who have not done well with older preventers, so they are usually offered after those have been tried. Benefit is judged over a few months, and treatment is reviewed to see whether attacks are reducing enough to continue. The most common issue is a reaction at the injection site, such as redness, itching or hardness, which is usually mild. It should not be used in pregnancy without specialist advice, and you should discuss it if you are planning a pregnancy or breastfeeding.
Who should not take it / use with caution
- It should not be used in pregnancy unless a specialist advises, and is best discussed before planning a pregnancy or while breastfeeding.
- People who have had a serious allergic reaction to fremanezumab or its ingredients should not use it.
- It is used with care in people with certain heart or blood-vessel conditions, who should discuss this with their specialist.
Monitoring
- Reviewing after a few months whether the number and severity of migraines has reduced enough to continue.
- Checking for injection-site reactions and any signs of an allergic reaction.
- Discussing pregnancy plans, breastfeeding and overall migraine control at review.
Side effects
- Reactions where the injection is given, such as redness, pain, itching or hardness, are the most common and are usually mild.
- Some people get constipation, itching or a rash.
- Rarely, a more serious allergic reaction can occur, which needs urgent medical attention.
Key interactions
- It has few known interactions with other medicines, as it works on CGRP rather than being processed like ordinary tablets.
- It can be used alongside acute migraine treatments for attacks, but tell your team about everything you take.
- Always tell your specialist about other preventer medicines so your overall migraine plan can be reviewed.
Available as: A pre-filled pen or syringe for injection under the skin.
Answers
Fremanezumab: frequently asked questions
Will fremanezumab stop a migraine I already have?
No. It is a preventer taken regularly to make migraines less frequent, so you still need a separate acute treatment for an attack that has already started.
How often do I need the injection?
It can be given either once a month or as a larger dose once every three months, depending on the schedule you and your specialist choose.
How long before I know if it is working?
Its benefit builds up gradually, so it is usually judged over a few months before deciding whether to continue.
Why was I only offered it after other medicines?
Anti-CGRP medicines are a newer class usually offered to people whose migraines have not responded to several older preventer medicines.
Can I use it in pregnancy?
It should not be used in pregnancy without specialist advice, so discuss it if you are pregnant, planning a pregnancy or breastfeeding.
The wider class
About Anti-CGRP biologic (migraine prevention)
Fremanezumab belongs to the anti-cgrp biologic (migraine prevention) class. For how the class as a whole works, its shared safety principles and monitoring, see the full guide.
Browse by body system
Authoritative sources
- BNF
- NICE CKS
Building a medicines information resource?
We create evidence-led, dose-free drug and formulary references for teams.