Hi there,
From the article that Lou posted from the BMJ publication re chronic migraine, the authors include this comment:
Be patient with prophylactic treatments. Patients with migraine often expect immediate results from new drugs. To improve adherence to treatment and reduce patient frustration, clinicians should make patients aware of the expected interval between starting a new drug and obtaining relief. Once the target dose is reached, six to eight weeks of treatment might be needed before maximum benefits are realized.
I personally found this approximate timeline to be true when I started Topamax. It took quite a few weeks/months once I hit my ideal dose to start feeling better (although I did notice small improvements as I was going up), and then the longer I took it the better I felt. The key is to be patient and stick it out. I think those who feel better immediately on any prophylactic drugs are in the minority, sadly. Most of these drugs take time to work on your system.
Good luck!
Regards,
Helen