Dopexamine hydrochloride is a new synthetic
catecholamine for intravenous use in
low cardiac output states with co-existing raised systemic or pulmonary vascular resistance.
Dopamine has been commonly used since several years in these situations. The drawbacks of
dopamine include a vasoconstrictive effect with high infusion rates, and a marked tendency for ventricular ectopy due to the potent beta-1
adrenergic stimulation.
Dopexamine hydrochloride has interesting
vasodilator properties, with marked intrinsic agonist activity at beta-2 adrenoreceptors and a lesser agonist activity at dopaminergic receptors (DA1 and DA2). Its mild inotropic activity arises primarily from baroreceptor reflex stimulation with a possible contribution from direct stimulation of myocardial beta 2-adrenoreceptors.
Dopexamine hydrochloride is responsible for an inhibition of neuronal re-uptake of
catecholamines (uptake-1), producing an indirect stimulation of cardiac beta 1-receptors. This
catecholamine has no effect at alpha 1 and alpha 2-adrenoreceptors, and only very weak and clinically insignificant beta 1-adrenoreceptor agonist activity.
Dopexamine hydrochloride improves cardiac performance by a marked vasodilation and a mild inotropic activity. The specific activity at dopaminergic receptors increases cerebral, myocardial, splanchnic and renal blood flows. These haemodynamic effects are associated with an increase in diuresis and natriuresis. These benefits are achieved without side effects such as an increased myocardial oxygen consumption, although induced
tachycardia may be responsible for
chest pain/anginae
pain in patients with ischaemic
heart disease. In clinical practice,
dopexamine hydrochloride is easy to use; the short plasma half-life (6 minutes in healthy volunteers and 11 minutes in patients with
low cardiac output) allows a rapid return to pretreatment status at discontinuation of the infusion. Preliminary studies have shown that
dopexamine hydrochloride can produce beneficial effects in patients with acute
heart failure or with compromised left ventricular function following cardiac surgery. The
drug has also been assessed in patients with
septic shock, most often in association with
dopamine or
norepinephrine. In these patients,
dopexamine produces a dose-related increase in cardiac index, stroke volume, heart rate and a decrease in systemic vascular resistance. Its use in this indication must be cautious, particularly in patients with
hypotension or decreased venous return. Comparative therapeutic trials are clearly required to establish the efficiency and tolerance of
dopexamine hydrochloride in comparison with
dopamine and
dobutamine, before its place in
therapy can fully be defined.