We have studied the pharmacokinetics of oxybutynin (Ditropan) after single oral (5 mg) and intravenous administration (1 and 5 mg), and after repeated oral administration in healthy volunteers. Oxybutynin was rapidly absorbed, maximum plasma concentrations (8 ng.ml-1) being reached in less than 1 h. The absolute systemic availability averaged 6% and the tablet and solution forms displayed similar relative systemic availability. Plasma concentrations of oxybutynin fell biexponentially, the elimination half-life being about 2 h. There was a large interindividual variation in oxybutynin plasma concentrations. Almost no intact drug could be recovered in the urine. During repeated oral administration steady-state was reached after eight days of treatment. The low absolute systemic availability of oxybutynin, the large interindividual variability in its plasma concentrations, and the apparent absence of intact oxybutynin in the urine suggest that its major pathway of elimination is hepatic metabolism.

1 The pharmacokinetics of cefuroxime have been investigated in 18 patients at least 70 years old. The drug was given either by continuous infusion (7 cases) or by multiple injections (11 cases) for 3 to 11 days (mean duration: 7 days). 2 The unchanged drug was assayed in blood plasma and in the urine by high performance liquid chromatography (h.p.l.c). 3 Cefuroxime was cleared, unchanged, almost exclusively by the kidneys, even when kidney function was impaired. Creatinine clearance ranged from 1.02 to 4.08 1/h (17 to 68 ml/min) in this group of patients and plasma clearance of cefuroxime varied from 1.02 to 8.16 1/h (17 to 136 ml/min) (r = 0.7 P less than 0.001 for linear correlation), but the apparent rate constant for nonrenal elimination remained quite small (average: 0.04 h‐1) and independent of creatinine clearance (r = 0.06, n = 17). 4 Since creatinine clearance decreases sharply with age, it might be suggested that cefuroxime dosage be related to creatinine clearance in the elderly, even when no renal impairment is suspected.

The pharmacodynamic effects of torasemide, a new potent loop diuretic, were compared with those of furosemide in a double blind controlled study in 18 hypertensive patients with oedema of various origins. Given orally for 5 days, torasemide was clinically very effective and well tolerated. On a weight basis, the diuretic, natriuretic and chloruretic effects of torasemide were about 8-times greater than those of furosemide. However, the kaliuretic effect of torasemide was only 3-times greater than that of furosemide, suggesting that torasemide is more potassium sparing than furosemide. Torasemide displayed a rapid onset of action, similar to that of furosemide but had a longer diuretic effect without any rebound phenomenon. Torasemide and furosemide did not effect creatinine clearance or uric acid excretion. Both furosemide and torasemide lowered systolic blood pressure but the effect of torasemide was more marked than that of furosemide. In this group of aged and hypertensive patients with oedema, the pharmacokinetics of torasemide was comparable to that reported in young healthy volunteers, and were similar on the first and fifth days of treatment. The long duration of action and the potassium sparing effect of torasemide compared to furosemide are promising features of this new loop diuretic in the treatment of oedema and hypertension.

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ESA administration has quantifiable labour and material costs which are affected by dosing frequency.