Mechanism of action<unk> 's antimigraine activity is due to its action as an agonist at the serotonin 5-HT1B, 5-HT1D, and 5-HT1F receptors. It also interacts with other serotonin, adrenergic, and dopamine receptors.<unk>  is an agonist of the serotonin 5-HT2B receptor and has been associated with cardiac valvulopathy. Pharmacodynamic + Site Affinity (Ki/IC50 nM) Efficacy (Emax %) Action 5-HT1A 0.4–1.5 ? Agonist 5-HT1B 0.006–18 ? Agonist 5-HT1D 0.13–0.5 ? Agonist 5-HT1E 1,100 ? ? 5-HT1F 180 ? Agonist 5-HT2A 9.0 ? Agonist 5-HT2B 15–33 ? Agonist 5-HT2C 1.3 ? Agonist 5-HT3 >3,700–>10,000 ? ? 5-HT4 60 ? ? 5-HT5A ? ? ? 5-HT5B ? ? 5-HT6 5.4 ? ? 5-HT7 9.1–9.2 ? ? α1A 6.6 ? ? α1B 8.3 ? ? α1D ? ? ? α2A 1.9 ? ? α2B 3.3 ? ? α2C 1.4 ? ? β1 3,100 ? ? β2 2,700 ? ? β3 271 ? ? D1 2,779 ? ? D2 1.2–5.0 ? Agonist D3 6.4–16 ? ? D4 8.7 ? ? D5 ? ? ? H1 ? ? ? mACh ? ? ? Notes: All receptors are human except 5-HT3 (rat/mouse), 5-HT4 (guinea pig), 5-HT5B (rat—no human counterpart), α1A-adrenergic (rat/human), and α2A-adrenergic (rat/human). Pharmacokinetics Oral bioavailability is poor and it is not available in oral form in the US.<unk>  is available as a nasal spray and in ampules for subcutaneous, intramuscular and intravenous injection. Efficacy is variable in the nasal spray form with relative bioavailability of 32% compared to injection.
Dihydroergotamine
Allergan
Dicycloverine
Piperoxan
Ergotamine
Oxymetazoline
Metergoline
Betahistine