Guanfacine-¹³C,¹⁵N₃is intended for us as an internal standard for the quantification of guanfacine by GC- or LC-MS. Guanfacine is an α₂-adrenergic receptor (α₂-AR) agonist with K_ivalues of 93, 1,380, and 3,890 nM for α_2A-, α_2B-, and α_2C-ARs, respectively, in a radioligand binding assay.¹It has EC₅₀values of 52, 288, and 602 nM for α_2A-, α_2B-, and α_2C-ARs, respectively, for stimulated [³⁵S]GTPγS binding. It also binds to imidazoline receptor 1 (K_i= 19 nM in a radioligand binding assay).²Guanfacine (0.3-5 mg/kg) binds to adrenergic receptors in the central nervous system and lowers blood pressure in hypertensive rats in a dose-dependent manner.³It also improves spatial working memory deficits induced by hypobaric hypoxia in rats.⁴Formulations containing guanfacine are used in the treatment of high blood pressure and attention deficit hyperactivity disorder (ADHD).

1.Jasper, J.R., Lesnick, J.D., Chang, L.K., et al.Ligand efficacy and potency at recombinant α2 adrenergic receptors: Agonist-mediated [35S]GTPγS bindingBiochem. Pharmacol.55(7)1035-1043(1998) 2.Nikolic, K., Filipic, S., and Agbaba, D.QSAR study of imidazoline antihypertensive drugsBioorg. Med. Chem.16(15)7134-7140(2008) 3.Scholtysik, G.Pharmacology of guanfacineBr. J. Clin. Pharmacol.10(Suppl 1)21S-24S(1980) 4.Kauser, H., Sahu, S., Kumar, S., et al.Guanfacine is an effective countermeasure for hypobaric hypoxia-induced cognitive declineNeuroscience254110-119(2013)