Ibopamine kinetics after single and multiple dosing in patients with congestive heart failure

The pharmacokinetics of ibopamine after single and multiple dosing was studied in 20 patients with congestive heart failure (CHF) of NYHA functional class II. Ibopamine 100 mg was given 3 times a day for 7 days in 6 patients and for 30 days in the other 14 patients. Plasma pharmacokinetics of total (mainly conjugated) and free epinine was studied after the first dose and on the 3rd, 7th and 30th days of treatment. The urinary recoveries of total epinine, HVA and DOPAC were measured in 5 patients for 24 h after ibopamine ingestion on the 1st and 30th days. Plasma pharmacokinetics of ibopamine did not vary during the repeated administration of the drug. In the course of the treatment, total epinine elimination t1/2 showed no significant variations. The build-up of Cmax, Cmin and AUC of total epinine observed after multiple dosing was as expected on the basis of the interval adopted between the doses of ibopamine and of the elimination t1/2 of total epinine. Pharmacokinetic parameters of free epinine did not show significant variations during the course of the treatment. The amounts of HVA and DOPAC recovered in urine on the 1st and 30th days of treatment were similar while the amount of total epinine was greater on the 30th day, the increment mainly reflecting a partial carry over of the less rapidly excreted conjugated epinine from the last previous doses. The results obtained for free epinine plasma levels and for the urinary recoveries of ibopamine metabolites thus indicated that no saturation of the enzymes involved in ibopamine metabolism occurred.