What does it imply if an adult can take Ajovy 225mg every two months instead of monthly? does it imply the 225mg dose is an overshoot for this particular person? if the half-life is 30 days and the drug works great for 60 days, what do we learn from that?

The short version: a patient who gets 60 days of benefit from a single 225 mg dose tells you the drug is being overdosed for that person, but the manufacturer never tested the lower doses that would confirm it.

The half-life of fremanezumab is about 30 days [2]. A drug that works for 60 days — two half-lives — means the concentration at day 60 is roughly one-quarter of the peak. If that quarter-dose still controls migraine, then the peak dose was at least four times higher than needed. The 225 mg monthly regimen was tested in the HALO trials and produced a reduction of about 5 migraine days per month in chronic migraine patients [2]. But those trials did not test a 175 mg dose or any other intermediate dose in adults [2]. The closest weight-based data comes from a pediatric study that modeled 120 mg monthly for children under 45 kg [1], suggesting the adult dose could be substantially lower.

The manufacturer, Teva, funded the pivotal trials [2]. Without a published dose-finding study that tested multiple intermediate doses, the evidence cannot tell you whether 175 mg, 150 mg, or even 100 mg would work as well for most patients. A patient who stretches the dose to 60 days is doing an n-of-1 experiment that the manufacturer never ran. The drug is approved at 225 mg monthly, but the evidence for that specific number as the optimal dose is absent from this retrieval.

My call: the 60-day response strongly suggests the 225 mg dose is an overshoot for that person, but the manufacturer never tested the lower doses that would prove it. Confidence: moderate for the overshoot inference, low for the dose-optimization question.