Isoprenaline Other names: N-Isopropylnorepinephrine N-Isopropylnoradrenaline L-Isopropylnoradrenaline Isoproterenol Isopropylnorepinephrine Isopropylnoradrenaline Isopropylarterenol Isopropyladrenaline Isopropydrin Isoprenaline Epinephrine Isopropyl Homolog

Isoprenaline hydrochloride (also called isoproterenol hydrochloride) is 3,4-Dihydroxy-alpha-(isopropylamino) methyl benzyl alcohol hydrochloride, a synthetic sympathomimetic amine that is structurally related to adrenaline but acts almost exclusively on beta adrenergic receptors.

Isoprenaline is a potent non selective beta-adrenergic agonist with low affinity for alphaadrenergic receptors.

Isoprenaline acts primarily on the heart and on smooth muscle of bronchi, skeletal muscle vasculature and the gastrointestinal tract.

Isoprenaline increases cardiac output due to its positive inotropic and chronotropic actions and increasing venous return. With usual therapeutic doses, the increase in cardiac output is generally sufficient to maintain or increase systolic blood pressure. Intravenous infusion of isoprenaline also lowers peripheral vascular resistance. The diastolic pressure, therefore, may be expected to fall in normal individuals. Thus the mean pressure may be reduced. The rate of discharge of cardiac pacemakers is increased with isoprenaline.

Isoprenaline relaxes most smooth muscle, the most pronounced effect being on bronchial and gastrointestinal smooth muscle. It produces marked relaxation in the smaller bronchi and may even dilate the trachea and main bronchi past the resting diameter.

In man, isoprenaline causes less hyperglycaemia than does adrenaline. Isoprenaline and adrenaline are equally effective in stimulating the release of free fatty acids and energy production.

Isoprenaline is readily absorbed when given parenterally.

The half-life of isoprenaline hydrochloride is brief lasting only a few minutes following intravenous administration and up to 2 hours after subcutaneous administration. Isoprenaline is metabolised by catechol-o-methyl transferase primarily in the liver. The major metabolite after intravenous administration is 3-0-methylisoprenaline, which is reported to have weak βadrenergic blocking activity, and its conjugates. Isoprenaline is a relatively poor substrate for MAO and is not taken up by sympathetic neurons to the same extent as adrenaline and noradrenaline. The duration of action of isoprenaline may therefore be longer than that of adrenaline, but it is still brief. The metabolites are excreted through the kidneys.

No data available.