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The results given are the mean +s.d. for 10 normal subjects, 10 coeliacs and 5 Crohns, unless otherwise indicated in parentheses. The T112 and ka values were derived by linear regression analysis.. Plasma concentration of a-methyldopa and sulphate conjugate after oral administration of methyldopa and methyldopa hydrochloride ethyl ether. Eur. Many physicians now treat diuretic-induced hypoka-laemia only when the plasma potassium concentration falls below 3.0 mmol/l. We have investigated the relations between plasma potassium and E.C.G. changes in patients treated with bendrofluazide and potassium-sparing drugs (Fraser, Hettiarachchi, Mor-ton, Ramsay & Shelton, 1978) seeking particularly a threshold effect which might support this arbitrary criterion for intervention. Fourteen hypertensive patients were treated with bendrofluazide 10 mg daily throughout the study and received, in addition, placebo , spironolactone at four doses (25, 50, 100 and 200 mg/day), and amiloride at three doses (5, 10 and 20 mg daily), each given for 4 weeks in a balanced crossover design. At the end of each treatment phase plasma potassium was measured and a 60s lead II E.C.G. trace was obtained. E.C.G. measurements were made without knowledge of the treatment or plasma potassium, and were corrected to the mean R wave height for individuals to allow for'variation in calibration. The results were not normally distributed and non-parametric statistical methods were used. During placebo treatment (i.e. bendrofluazide

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Absrruct.The elimination from plasma of IT-labelled methyldopa was studied in three bilaterally nephrectomized patients and four patients with reduced renal function. The elimination of radioactivity was slow, particularly in the anephric patients where about 50% of the injected dose was still present in plasma after 48 hours. Chemically determined methyldopa disappeared from plasma much faster than radioactivity in both groups of patients, suggesting formation and retention of metabolite(s). The urinary excretion rate of both radioactivity and unchanged drug in the patients with renal failure was slow in comparison with normal subjects. Moreover, the composition of the 0-48 hour urine differed from that of normals, showing a lowered content of unchanged drug. Slow elimination of unidentified metabolite(s) might possibly explain the strong and prolonged hypotensive action of methyldopa in patients with renal failure. Hansen, T. 1977. Pharrnacokinetics of methyldopa in normal man. Eur J Clin Plznrmacol 12, 117. Scand J Urol Nephrol 16 Scand J Urol Nephrol Downloaded from informahealthcare.com by Chulalongkorn University on 12/26/14 For personal use only.

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