Efaroxan (hydrochloride)

Efaroxan is an α₂-adrenergic receptor (α₂-AR; EC₅₀s = <10 µM) and imidazoline I₁ receptor antagonist.¹ It binds to α_2A-, α_2B-, and α_2C-ARs (K_is = 13, 38, and 1,820 nM, respectively) and selectively to I₁ over I₂ receptors (K_is = 52 and >10,000 nM, respectively). Efaroxan is an I₃ agonist that binds to putative I₃ receptors on human pancreatic islets of Langerhans and stimulates insulin secretion when used at a concentration of 100 μM.² It also binds to rat RIN-5AH insulinoma cell membranes (IC₅₀ = 32 nM) and stimulates insulin secretion when used at a concentration of 100 μM.³ Efaroxan (5 mg/kg) lowers basal blood glucose levels in mice.⁴ It also increases 3,4-dihydroxyphenylalanine (L-DOPA; Item No. 13248) synthesis in rat cortex and hippocampus by 77 and 57%, respectively, when administered at a dose of 10 mg/kg.⁵

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1. Eglen, R.M., Hudson, A.L., Kendall, D.A., et al. 'Seeing through a glass darkly': Casting light on imidazoline “I” sites. Trends Pharamacol. Sci. 19(9), 381-390 (1998).

2. Cooper, E.J., Hudson, A.L., Parker, C.A., et al. Effects of the β-carbolines, harmane and pinoline, on insulin secretion from isolated human islets of Langerhans. Eur. J. Pharmacol. 482(1-3), 189-196 (2003).

3. Olmos, G., Kulkarni, R.N., Munirul, H., et al. Imidazolines stimulate release of insulin from RIN-5AH cells independently from imidazoline I₁ and I₂ receptors. Eur. J. Pharmacol. 262(1-2), 41-48 (1994).

4. Mayer, G., and Taberner, P.V. Effects of the imidazoline ligands efaroxan and KU14R on blood glucose homeostasis in the mouse. Eur. J. Pharmacol. 454(1), 95-102 (2002).

5. Saster-Coll, A., Esteban, S., and Garcia-Sevilla, J.A. Effects of imidazoline receptor ligands on monoamine synthesis in the rat brain in vivo. Naunyn Schmiedebergs Arch. Pharmacol. 360(1), 50-62 (1999).