Erenumab

• Migraine Prevention
• Chronic Migraine
• Episodic Migraine
• CGRP-Targeted Therapy

Erenumab is a fully human monoclonal antibody that targets the calcitonin gene-related peptide (CGRP) receptor, used for the preventive treatment of migraine. This was the first FDA-approved CGRP pathway-targeted therapy specifically developed for migraine prevention.

Mechanism of Action

Erenumab binds to and blocks the calcitonin gene-related peptide receptor (CGRP-R). CGRP is a 37-amino acid neuropeptide widely distributed in the central and peripheral nervous systems that plays a crucial role in migraine pathophysiology. During a migraine attack, CGRP is released from trigeminal sensory neurons and causes vasodilation, neurogenic inflammation, and sensitization of pain pathways. By blocking the CGRP receptor, erenumab prevents CGRP-mediated signaling, reducing the frequency and severity of migraine attacks. Unlike small molecule CGRP antagonists (gepants), erenumab provides continuous receptor blockade through monthly dosing.

Available Formulations

Erenumab is available as a solution for subcutaneous injection in prefilled single-dose autoinjectors and prefilled syringes containing 70 mg/mL or 140 mg/mL. The medication requires refrigeration but can be kept at room temperature (up to 77°F/25°C) for up to 7 days. Patients can self-administer after proper training. Injection sites include the abdomen, thigh, or upper arm.

Medical Uses

Erenumab is FDA-approved for the preventive treatment of migraine in adults. It is effective for both episodic migraine (less than 15 headache days per month) and chronic migraine (15 or more headache days per month). Clinical trials demonstrated significant reductions in monthly migraine days compared to placebo. The medication can be used with other preventive migraine medications. It is not intended for the acute treatment of migraine attacks.

Dosing Guidelines

The recommended dose is 70 mg or 140 mg administered subcutaneously once monthly. Some patients may benefit from the 140 mg dose. The medication should be injected at approximately the same time each month. If a dose is missed, it should be administered as soon as possible, then resume the regular monthly schedule. No dose titration is required. Clinical benefit may be observed as early as the first month, but some patients may take up to 3 months to respond.

Important Safety Information

Constipation is a common side effect that can be severe in some cases, requiring hospitalization in rare instances. Patients should be counseled about constipation management strategies. Hypertension has been reported; blood pressure should be monitored, especially in patients with pre-existing hypertension. Hypersensitivity reactions including rash, angioedema, and anaphylaxis have occurred. The medication is contraindicated in patients with serious hypersensitivity to erenumab or any excipients.

Drug Interactions

No formal drug interaction studies have been conducted. Erenumab is not expected to undergo hepatic metabolism or interact with cytochrome P450 enzymes as it is a monoclonal antibody eliminated through catabolism. It can be used concomitantly with acute migraine treatments (triptans, ergots, NSAIDs) and other preventive medications (beta-blockers, anticonvulsants, antidepressants).

Special Populations

There are no adequate data on use during pregnancy. Animal studies did not show adverse developmental effects. Women should be advised of potential risks. It is unknown whether erenumab is excreted in human breast milk; the developmental and health benefits of breastfeeding should be considered. Safety and efficacy have not been established in pediatric patients. Clinical trials included patients aged 18-65; no overall differences in safety were observed in elderly patients in limited numbers. No dose adjustment is needed for renal or hepatic impairment.