Eletriptan HBr is a selective 5-HT1B and 5-HT1D receptor agonist with Ki of 0.92 nM and 3.14 nM, respectively.IC50 value: 0.82 nM/3.14 nM (5-HT1B/5-HT1D, Ki) [1]Target: 5-HT1B/5-HT1D in vitro: [3H]Eletriptan has a total number of binding sites (Bmax) of 2478 fmol/mg and 1576 fmol/mg for 5-HT1B and 5-HT1D, respectively. [3H]Eletriptan has a significantly faster association rate (K(on) 0.249/min/nM) than [3H]sumatriptan (K(on) 0.024/min/nM) and a significantly slower off-rate (K(off) 0.027/min compared to 0.037/min for [3H]sumatriptan) [1]. Eletriptan induces concentration-dependent contractions of meningeal artery, coronary artery, and saphenous vein. The potency of Eletriptan is higher in meningeal artery than in coronary artery (86-fold) or saphenous vein (66-fold). The predicted contraction by Eletriptan (40 mg and 80 mg) and sumatriptan (100 mg) at free C(max) observed in clinical trials is similar in meningeal artery [2].in vivo: Eletriptan (<1000 mg/kg, i.v.) produces a dose-dependent reduction of carotid arterial blood flow in the anaesthetised dog. Eletriptan reduces coronary artery diameter with ED50 value of 63 mg/kg in the anaesthetised dog. Eletriptan (<300 mg/kg, i.v.) administered prior to electrical stimulation of the trigeminal ganglion produces a dose-related and complete inhibition of plasma protein extravasation in the dura mater rats. Eletriptan (100 mg/kg, i.v.) produces a complete inhibition of plasma protein extravasation in rat dura mater [3]. Iontophoretic ejection (50 nA) of Eletriptan suppresses the response in 75% of cells and causes an average suppression of cell firing of 42% in cats [4].
References:
[1]. Napier C, et al. Characterisation of the 5-HT receptor binding profile of eletriptan and kinetics of [3H]eletriptan binding at human 5-HT1B and 5-HT1D receptors. Eur J Pharmacol, 1999, 368(2-3), 259-268.
[2]. MaassenVanDenBrink A, et al. Craniovascular selectivity of eletriptan and sumatriptan in human isolated blood vessels. Neurology, 2000, 55(10), 1524-1530.
[3]. Gupta P, et al. The in vivo pharmacological profile of eletriptan (UK-116,044): a potent and novel 5-HT(1B/1D) receptor agonist. Eur J Pharmacol, 2000, 398(1), 73-81.
[4]. Hoskin KL, et al. The 5-hydroxytryptamine1B/1D/1F receptor agonists eletriptan and naratriptan inhibit trigeminovascular input to the nucleus tractus solitarius in the cat. Brain Res, 2004, 998(1), 91-99.