Chemical formula: C₈H₁₁NO₂ Molecular mass: 153.178 g/mol PubChem compound: 681
Dopamine hydrochloride stimulates adrenergic receptors of the sympathetic nervous system. Dopamine hydrochloride has principally a direct stimulatory effect on β1-adrenergic receptors, but also appears to have an indirect effect by releasing norepinephrine from its storage sites. Dopamine hydrochloride also appears to act on specific dopaminergic receptors in the renal, mesenteric, coronary, and intracerebral vascular beds to cause vasodilation. Dopamine hydrochloride has little or no effect on β2-adrenergic receptors.
At higher doses (10 to 20 μg/kg/min), dopamine hydrochloride can also stimulate alpha-1 receptors, resulting in vasoconstriction and increased peripheral vascular resistance.
Orally administered dopamine hydrochloride is rapidly metabolised in the gastrointestinal tract. Following IV administration, the onset of action of dopamine hydrochloride occurs within 5 minutes, and dopamine hydrochloride has duration of action of less than 10 minutes.
Dopamine is widely distributed in the body but does not cross the blood-brain barrier to a substantial extent. It is not known if dopamine crosses the placenta.
Dopamine hydrochloride has a plasma half-life of about 2 minutes. Dopamine hydrochloride is metabolised in the liver, kidneys, and plasma by MAO and catechol-O-methyltransferase to the inactive compounds homovanillic acid (HVA) and 3, 4-dihydroxyphenylacetic acid. In patients receiving MAO inhibitors, the duration of action of dopamine hydrochloride may be as long as 1 hour. About 25% of a dose of dopamine hydrochloride is metabolised to norepinephrine within the adrenergic nerve terminals.
Dopamine hydrochloride is excreted in urine principally as HVA and its sulfate and glucuronide conjugates and as 3, 4-dihydroxyphenylacetic acid. A very small fraction of a dose is excreted unchanged. Following administration of radio labelled dopamine hydrochloride, approximately 80 % of the radioactivity reportedly is excreted in urine within 24 hours.
Elimination half-life in neonates is between 5 and 11 minutes. In critically ill infants and children clearance reportedly ranges from 48 to 168 mL/kg/min with the higher values reportedly in younger patients.
Clearance of dopamine hydrochloride is unpredictable in infants, particularly neonates. Clearance may be as much as 2-fold greater in those < 2 years of age.
Substantial interindividual variation was seen in dopamine hydrochloride pharmacokinetics in seriously ill infants, and plasma concentrations could not be predicted accurately from its infusion rate. Marked variation in clearance explains in part, the wide dose requirements of dopamine hydrochloride.
Available data suggest that dopamine hydrochloride and pharmacokinetics are similar to those in adults. Wide interindividual variability has been noted. A consistent relationship between clearance and age has not been demonstrated.
There is no pre-clinical data of relevance to the prescriber which are additional to that already included in other sections of this summary of product characteristics.
Standardized reproductive toxicity studies were not performed for dopamine hydrochloride. Studies available show conflicting results.
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