[Ibopamine--pharmacologic principles].

Abstract

Ibopamine is the 3,4-diisobutyrylester of N-methyl-dopamine (epinine). Oral ibopamine is transferred during and after resorption (first-pass effect) to the active metabolite epinine by blood and tissue esterases. 200 mg ibopamine lead to maximal plasma concentrations of 60 to 100 nmol/l. The ratio of total epinine to free epinine is about 10:1. Epinine is intensively metabolized so that less than 1% of the oral dosage is eliminated via the kidneys. The plasma half-life of epinine amounts to about 45 min. Epinine activates dopamine (DA1, DA2)-, beta 1- and beta 2- as well as alpha-receptors. The affinity is of the other: DA1, DA2 greater than beta 1, beta 2 greater than alpha. Stimulation of postsynaptic DA1-receptors predominantly induces renal vasodilation and increase in diuresis. Stimulation of presynaptic DA2-receptors leads to a reduced liberation of noradrenaline (NA) from its presynaptic storage vesicles. This effects a decrease in NA-plasma concentration, peripheral resistance, and it is partly responsible for diuresis and natriuresis. Investigations in isolated organs have shown that the action on DA1, DA2-receptors occurs in the range of 100-700 nmol/l), whereas stimulation of beta 1- and beta 2-receptors affords significantly higher levels (affinity to human cardiac beta 1- and beta 2-receptors 5-10 mumol/l). alpha-receptors are only stimulated at still higher concentrations.(ABSTRACT TRUNCATED AT 250 WORDS)