CGRP Injections for Migraine: A Full Guide

Written and medically reviewed by Tae Ho Guak, MD, board-certified neurologist · Reviewed July 2026 · Editorial policy

For patients whose migraines are not adequately controlled with conventional preventive medications (beta-blockers, anticonvulsants, tricyclic antidepressants) or who have discontinued treatment due to adverse effects, CGRP (calcitonin gene-related peptide) monoclonal antibodies are preventive treatments designed to reduce migraine occurrence through injections administered once monthly or quarterly. This article outlines the mechanism of action and clinical evidence in the first section, and self-management strategies before and after treatment in the second section.

Medical Background — What is CGRP and Why is it a Target

CGRP is a neuropeptide secreted in the trigeminal vascular system and is recognized as a key substance in migraine attacks, mediating blood vessel dilation, neurogenic inflammation, and pain signal transmission. The observation that CGRP levels rise during attacks and that intravenous CGRP infusion triggers attacks in migraine patients provides the rationale for this target. Monoclonal antibodies block this pathway by binding to either the CGRP ligand itself (fremanezumab, galcanezumab, eptinezumab) or the CGRP receptor (erenumab). While oral gepants are small-molecule antagonists, these antibody-based agents have a large molecular size and long half-life, enabling administration once monthly or once quarterly.

Indications and Target Patients — Who Should Consider This Treatment

Generally, patients with 4 or more migraine days per month who have attempted at least 2 conventional preventive medications at adequate doses and durations but experienced insufficient efficacy, adverse effects, or contraindications are candidates for episodic or chronic migraine treatment. In Korea, insurance coverage may be applicable for patients meeting certain criteria such as chronic migraine, but coverage criteria and prior authorization requirements vary by timing and product, so confirmation before prescription is necessary. The routes of administration are subcutaneous injection (self-administered or at a clinic) for erenumab, fremanezumab, and galcanezumab, and intravenous injection (quarterly) for eptinezumab. In clinical trials, these agents meaningfully reduced the number of migraine days per month compared to placebo, and approximately half of patients reported a 50% or greater reduction in attack frequency. However, individual response varies considerably, and observation for approximately 3 months is typically recommended to assess efficacy.

Safety and Self-Management — What to Attend to Before and After Administration

Overall tolerability is generally good, but the most common adverse reactions are injection site reactions (erythema and pain) and constipation, with constipation being relatively more frequent in receptor-targeted agents. The following self-management strategies are helpful.

• Maintaining a headache diary: Recording attack frequency, severity, and acute medication use for at least 1 month before starting treatment objectifies efficacy assessment.
• Self-injection hygiene: Allow refrigerated syringes to reach room temperature for approximately 30 minutes before administration, and rotate injection sites (abdomen, thigh, etc.) with each injection.
• Constipation management: Increase fluid and dietary fiber intake, and consult with your healthcare provider about laxative use if constipation is severe.
• Concurrent acute treatment: Since preventive injections do not eliminate attacks entirely, maintain a plan for acute medications such as triptans or gepants when attacks occur, while avoiding overuse (medication overuse headache).
• Share pregnancy and breastfeeding plans: Safety data are limited, so inform your healthcare provider in advance if you are planning pregnancy.

Warning Signs Requiring Immediate Medical Evaluation

The following are warning signs of alternative etiologies rather than common adverse effects of preventive injection and require immediate medical evaluation: thunderclap headache reaching peak intensity within seconds to 1 minute, headache accompanied by fever and neck stiffness, neurological deficits (paralysis, diplopia, speech disturbance), new-onset headache after age 50 or headache markedly different from the patient’s usual pattern, severe allergic reactions such as facial or lip swelling or dyspnea after injection.

Conclusion

CGRP monoclonal antibodies have expanded the practical treatment options for migraine patients who have failed conventional preventive therapies or experienced limiting adverse effects. However, these agents do not work equally well for all patients, and efficacy is maximized when indications, insurance coverage criteria, and concurrent acute treatment are carefully coordinated. If migraine frequency is high and disrupting daily life, we recommend discussing a preventive treatment strategy with a headache specialist.

Reference: International Classification of Headache Disorders, 3rd edition (ICHD-3) and randomized controlled trials of CGRP-targeted preventive therapies (erenumab STRIVE/ARISE, fremanezumab HALO, galcanezumab EVOLVE, eptinezumab PROMISE series).

This article is provided for general medical information purposes and does not replace individual diagnosis or prescription. Treatment decisions should always be made in consultation with your healthcare provider.