Effect of intravenous dopamine infusion on plasma concentrations of dopamine and dopamine sulfate in men, during and up to 18 h after infusion

Objective: We investigated whether sulfoconjugation contributes to the inactivation of intravenously infused dopamine (DA) in low concentrations with a predominant action on the kidney. Methods: Plasma DA and dopamine sulfate (DA-S) concentrations were determined during 4 h of intravenous infusion of DA (2 μg/kg/min) and up to 18 h after cessation of infusion. Twenty-seven healthy young subjects participated in the placebo controlled, randomised and double-blind study. Results: Intravenously administered DA was sulfoconjugated rapidly and to a great extent. After starting the infusion, DA levels rose within minutes and reached a steady state after 30–60 min. The steady-state levels averaged 151.3 ± 8.2 nmol/l. DA-S levels also increased markedly with infusion from 16.7 ± 9.9 nmol/l at the start of infusion up to 261.2 ± 24.2 nmol/l at 30 min after cessation of infusion. Plasma DA concentrations after cessation of the infusion decreased rapidly with an initial half-life of elimination of 4.8 min. Concentrations of plasma DA-S declined with a half-life of 4.5 h. Persistent elevations of free and conjugated DA compared with pre-treatment levels were observed even 18 h after cessation. Heart rate and blood pressure remained unchanged both during DA and saline infusion. Conclusion: Findings indicate that the sulfoconjugation pathway contributes markedly to the inactivation of intravenously infused DA and seems not to be saturable by DA infusion in low doses. Received: 8 March 1999 / Accepted in revised form: 21 September 1999