Dapiprazole is an α-adrenergic receptor (α-AR) antagonist.1 It inhibits norepinephrine-induced contractions in rat vas deferens, guinea pig spleen, and rat aorta, regions that express high levels of α1A-AR, α1B-AR, and α1D-ARs, respectively (pA2s = 7.93, 7.13, and 8.26, respectively). It also inhibits contractions induced by histamine, angiotensin II, pentagastrin , carbamoylcholine , and serotonin in guinea pig ileum in a dose-dependent manner.2 Dapiprazole (0.05%, intracameral) reverses pupil dilation induced by a combination of the α1A-AR agonist phenylephrine and the muscarinic M4 antagonist tropicamide in rabbits.3 Formulations containing dapiprazole have been used in the treatment of iatrogenically induced mydriasis by adrenergic or parasympatholytic agents in certain eye examinations.
1.Eltze, M.Affinity of the miotic drug, dapiprazole, at α1-adrenoceptor subtypes A, B and DJ. Pharm. Pharmacol.49(11)1091-1095(1997) 2.Lograno, M.D., and Reibaldi, A.Effects of dapiprazole on contractile responses of guinea pig isolated ileumPharmacol. Res. Commun.19(3)209-221(1987) 3.Bonomi, L., Marchini, G., Pagello, P., et al.Effects of intraocular dapiprazole in the rabbit eyeJ. Cataract Refract. Surg.15(6)681-684(1989)