The pharmacokinetics and pharmacodynamics of bumetanide (1 mg) administered either orally or intravenously were studied in a group of normal subjects using high-pressure liquid chromatography. A two-compartment model adequately fitted the intravenous data. Renal clearance (85 ml min-1) contributed 65% to the total elimination of bumetanide irrespective of whether a model-dependent or model-independent method was used. Oral administration of bumetanide elicited a greater and a more prolonged pharmacological response than did intravenous bumetanide. An attempt is made to relate the pharmacokinetics of the drug to its pharmacodynamics.

1Bumetanide (1 mg) was given orally and intravenously to a group of patients with chronic renal failure (n = 6) and to another group with cirrhosis of the liver (n = 8). 2 The pharmacokinetics, using a two-compartment model, and the pharmacodynamics of the drug in these patients were compared with those previously obtained for normal subjects. 3 In the renal group serum bumetanide concentrations were higher than for the normal subjects and the terminal half-lives were significantly prolonged (P < 0.001). A decreased whole body clearance was attributable to a low renal clearance of drug, the non-renal clearance being significantly increased (P < 0.01). 4 For the patients with liver disease, serum bumetanide concentrations were higher than for the renal group, and the terminal half-lives were significantly further prolonged (P < 0.001). Both non-renal and renal clearances were significantly reduced (P < 0.001). 5 Absorption rates were not significantly altered in either group and the values of F (bioavailability) were 0.82 and 0.95 for the patients with renal disease and hepatic disease, respectively. 6 A poor pharmacodynamic response and a reduced bumetanide excretion rate were observed for the patients with chronic renal failure, whereas with hepatic disease normal bumetanide excretion rates were observed with an impaired diuretic response.

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Chronic administration of cimetidine was found to produce a fall in steady-state plasma concentrations of chlorpromazine and of indomethacin in patients. In each case there was some evidence of inhibition of metabolism, suggesting that the mechanism must therefore be decreased absorption sufficient to over-ride the metabolic change. This was confirmed by measurement of excretion of metabolites in the indomethacin study. The fall in indomethacin plasma concentrations was not associated with a change in the clinical effectiveness of the anti-inflammatory therapy.