Migraine is a complex neurological disorder that affects a significant 
proportion of the adult population worldwide. It is associated with an increase 
in plasma calcitonin gene-related peptide (CGRP) level. CGRP, a neuropeptide 
released from activated trigeminal sensory nerves, dilates intracranial blood 
vessels and transmits vascular nociception. Therefore, it is proposed that CGRP 
may have an important role in migraine pathophysiology and inhibition of 
trigeminal CGRP release or CGRP-induced cranial vasodilatation may abort 
migraine. The mode of action of CGRP antagonists is inhibition of neurogenic 
vasodilatation and inflammation, an additional neuronal action cannot be ruled 
out. Both intravenous applied olcegepant (BIBN 4096) and the oral telcagepant 
(MK-0974) were tested in clinical trials and showed clinical benefit and 
excellent tolerability, with recent presentation of phase III data on 
telcagepant suggesting that proof of concept is positive. CGRP receptor 
antagonists terminate migraine with efficacy similar to triptans. The results 
from clinical trials suggest that this new type of drug might offer advantages 
over existing therapies without vasoconstrictive or vascular side effects.