ICI 118551 (10 μM) induces a prominent vasorelaxation of norepinephrine (NE)-precontracted PA but not AO [2]. ICI 118551 inhibits cAMP accumulation in IMCD cells (IC50: 1.7 μM) [1]. In the failing human heart, ICI 118551 has significant effects on beat duration, with time-to-peak contraction and time-to-90% relaxation reduced compared with basal contraction. Negative Inotropic Effect of ICI 118551 Is Not cAMP-Related. Overexpression of β2AR in rabbit myocytes enhances the negative inotropic effects of ICI 118551 [3].

ICI 118551 (0.2 mg/kg) injected into the jugular vein of the mice, strongly reduces systolic pressure in the pulmonary circuit but not systemic arterial pressure in vivo[2].