<unk>  appears to act by indirect stimulation of β-adrenergic receptors causing the release of norepinephrine from its storage sites. It has a positive inotropic effect on the myocardium. AV conduction and refractory period of AV node is shortened with an increase in ventricular conduction velocity. It dilates arteries and arterioles in the skeletal muscle and mesenteric vascular beds, leading to an increase in venous return. Its onset is 5 to–15 minutes with intramuscular dosing, and immediate with intravenous dosing. Its duration of action is four hours with intramuscular dosing and 30 minutes with intravenous dosing.
Mephentermine
Adatanserin
Phentermine
Clonidine
Tropisetron
Granisetron
Alosetron
Brimonidine