Anti-CGRP monoclonal antibody Pregnancy: There is a limited amount of data from use in pregnant women and no adequate data on developmental risk; animal studies do not indicate reproductive toxicity. As a precautionary measure it is preferable to avoid use during pregnancy. Fremanezumab has a long half-life, which should be taken into consideration for women who are pregnant or plan to become pregnant. Breast-feeding: it is unknown whether fremanezumab is excreted in human milk; a risk to breast-fed infants cannot be excluded during the first days after birth, after which use could be considered during breast-feeding only if clinically needed.

Fremanezumab

Brand names: Ajovy

Fremanezumab is a humanised monoclonal antibody given by subcutaneous injection for the prophylaxis of migraine in adults with frequent attacks.

Auto-extracted from the source labelling — not yet independently clinician-verified. These values were distilled from the UK SPC (or the US label where noted) but have not had a clinician sign-off. Confirm against the current SmPC before prescribing.

Adult dose

Dose: 225 mg once monthly, OR 675 mg every three months (quarterly), the quarterly dose being given as three consecutive subcutaneous injections of 225 mg each

Route: Subcutaneous injection only — must NOT be administered by the intravenous or intramuscular route. Inject into areas of the abdomen, thigh or upper arm that are not tender, bruised, red or indurated; alternate injection sites for multiple injections.

Frequency: Monthly dosing (225 mg once monthly) or quarterly dosing (675 mg every 3 months)

Migraine prophylaxis. Treatment should be initiated by a physician experienced in the diagnosis and treatment of migraine, and is intended for patients with at least 4 migraine days per month at initiation. When switching dosing regimens, the first dose of the new regimen should be given on the next scheduled dosing date of the prior regimen. Concomitant migraine preventive treatment may be continued if the prescriber considers it necessary. Treatment benefit should be assessed within 3 months of initiation, with any further decision to continue taken on an individual patient basis and re-evaluated regularly thereafter. MISSED DOSE: resume dosing as soon as possible on the indicated dose and regimen; a double dose must not be administered to make up for a missed dose. ELDERLY: limited data in patients >=65 years, but no dose adjustment is required based on population pharmacokinetics. Patients may self-inject if instructed in subcutaneous self-injection technique by a healthcare professional. PAEDIATRIC: the UK SPC states that safety and efficacy in children and adolescents below 18 years have not yet been established and no data are available. The US label additionally states a dosage of 225 mg monthly for the preventive treatment of episodic migraine in paediatric patients 6 to 17 years of age weighing 45 kg or more, and that it is not approved in paediatric patients weighing less than 45 kg (no appropriate strength presentation); this is not a per-kg dose. Verify any paediatric use against a children's formulary.

Dose adjustments

Renal

No dose adjustment is necessary in patients with mild to moderate renal impairment (or hepatic impairment).

Dose auto-extracted from UK Summary of Product Characteristics (SPC) via the eMC; US FDA prescribing information (openFDA / DailyMed) — cross-check; US labelling may differ from UK — not yet clinician-verified. Always confirm against the product SmPC and your local formulary before prescribing.

Contraindications

Hypersensitivity to the active substance or to any of the excipients

Side effects

Injection site pain (24%) — very common
Injection site induration (17%) — very common
Injection site erythema (16%) — very common
Injection site pruritus (2%) — common; injection site rash — uncommon
Hypersensitivity reactions such as rash, pruritus, urticaria and swelling — uncommon; anaphylactic reaction — rare

Interactions

No formal clinical drug interaction studies have been performed; no pharmacokinetic drug interactions are expected based on the characteristics of fremanezumab (§4.5)
Fremanezumab is not metabolised by cytochrome P450 enzymes, so interactions with CYP substrates, inducers or inhibitors are unlikely
Concomitant acute migraine treatments (analgesics, ergots, triptans) and migraine preventive medicinal products did not affect fremanezumab pharmacokinetics in clinical studies
Post-marketing: one patient taking multiple concomitant medications including lamotrigine developed Stevens-Johnson Syndrome; this has also rarely been reported with other anti-CGRP monoclonal antibodies with concomitant lamotrigine (§4.4)

Clinical monograph

How it works

It binds calcitonin gene-related peptide (CGRP) ligand, blocking its interaction with the receptor and reducing the trigeminovascular signalling that contributes to migraine.

Prescribing in practice

Hypersensitivity reactions including rash, pruritus and, rarely, anaphylaxis can occur, so advise patients on recognising and reporting these.
It is recommended for patients with frequent migraine in whom previous preventive treatments have been unsuccessful, in keeping with NICE guidance.
Review effectiveness after an adequate treatment period and stop if migraine frequency is not meaningfully reduced.

Monitoring

No routine laboratory monitoring is required, but headache frequency should be tracked and patients observed for hypersensitivity reactions.

Counselling the patient

This is a preventive injection to reduce migraine frequency, not a treatment for an individual attack.
Report any rash, swelling or breathing difficulty after injecting.
Keep a headache diary to help judge whether the treatment is helping.

Evidence & guidelines

NICE recommends fremanezumab for migraine prophylaxis in defined circumstances, supported by randomised trials showing reduced monthly migraine days versus placebo.

Reference: NICE TA631/TA764; SmPC; Drug verified in RxNorm (NLM); confirm dosing against the manufacturer SPC (eMC). Verify against your local formulary and current prescribing references before prescribing. The structured dose values shown have been reviewed by a clinician. Monograph status: clinician-reviewed (2026-07-04).

Curated clinical cross-links plus same-class fallbacks.

Calculators

Drugs

Galcanezumab · Anti-CGRP monoclonal antibody

Pathways