Does Ajovy (Fremanezumab) Affect Menstrual Cycles?
Based on available evidence, there is no documented effect of fremanezumab on menstrual cycles. The drug's mechanism of action—selectively targeting calcitonin gene-related peptide (CGRP)—does not involve hormonal pathways that regulate menstruation, and clinical trials have not reported menstrual irregularities as adverse events.
Mechanism and Safety Profile
Fremanezumab is a fully humanized monoclonal antibody (IgG2Δa) that selectively targets CGRP, a vasodilatory neuropeptide involved in migraine pathophysiology, without affecting sex hormone pathways. 1
The most common adverse events reported across clinical trials include injection-site pain and upper respiratory tract infections, with no mention of menstrual cycle disturbances. 2
Unlike erenumab (another CGRP antagonist), fremanezumab has not been associated with development or worsening of hypertension in post-marketing studies, suggesting a favorable safety profile without systemic hormonal effects. 2
Clinical Trial Evidence
Large-scale studies including the UNITE trial (353 patients) and real-world effectiveness studies (165 patients) documented adverse events comprehensively but did not report menstrual irregularities. 3, 4
The drug has been studied in adult women (who comprised 88% of participants in major trials) without any reported menstrual cycle changes. 3
Hormonal Context
While sex hormones (estrogen and progesterone) do fluctuate during the menstrual cycle and can affect migraine patterns, fremanezumab does not interact with these hormonal pathways. 5
Estrogen levels naturally influence migraine frequency, particularly in menstrually-related migraine, but CGRP antagonism does not alter estrogen or progesterone production or metabolism. 6
Fremanezumab can be safely used throughout the menstrual cycle without requiring timing adjustments or dose modifications based on cycle phase. 2
Practical Considerations
Patients can initiate fremanezumab at any point in their menstrual cycle without concern for cycle disruption. 1
If menstrual irregularities occur after starting fremanezumab, alternative causes should be investigated rather than attributing them to the medication. 2
The medication does not require contraceptive considerations beyond standard reproductive planning, unlike medications such as valproate which is absolutely contraindicated in women of childbearing potential. 2