Diuretics

Abstract

Despite the bewildering number of diuretics available to the physician, these drugs can be divided into 4 main groups, characterised by their site of action on sodium reabsorption in the kidney. Drugs acting on the ascending limb of the loop of Henle have a powerful but short acting diuretic effect; they include frusemide, ethacrynic acid and bumetanide. The benzothiadiazines and related compounds have a moderate diuretic action spread over a longer period, whilst the potassium-sparing diuretics, triamterene, amiloride and spironolactone, have only a weak diuretic effect but a marked ability to diminish urinary potassium excretion. The fourth group is made up of miscellaneous substances which function as vasodilator or osmotic agents. The pathogenesis of oedema formation in heart failure is outlined and a logical approach to treatment suggested. Duiretics are being increasingly used in the treatment of non-oedematous states, in particular hypertension, diabetes insipidus and hypercalciuria; their exact role in pregnancy and acute renal failure remains controversial. Side-effects can be related to their effect on electrolyte excretion and include hypokalaemia, hyponatraemia, hyperkalaemia and hyperuricaemia. The incidence of disturbed carbohydrate tolerance in previously normal individuals is low. Other less common side-effects are also discussed.

Longterm Experience of the Routine Use of Bumetanide

“…No unequivocal evidence of carbohydrate intolerance has been reported in other longterm studies (Olesen et al , 1973; Davies et al , 1974; Murdoch and Auld, 1975; Singh and Watt, 1975). Thus, there is no evidence that bumetanide precipitates diabetes; neither could we confirm the statement of Davies and Wilson (1975) that there is an increased risk of disturbing the control of non‐insulin dependent patients. We treated 9 diabetics and Murdoch and Auld (1975) 5 diabetics, but in no case was the control of diabetes affected by bumetanide.…”

Acute blood pressure and urinary responses to single dose combinations of captopril and diuretics in conscious spontaneously hypertensive rats

“…Furthermore, equipotent diuretic doses of frusemide, metolazone and hydrochlorothiazide produced similar B P lowering in combination with captopril. In contrast, triamterene, a K-sparing compound with modest natriuretic potency (Davies & Wilson 1975), caused a moderate increase in Na excretion but without diuresis and failed to augment the B P effect of captopril. Taken together, the results suggest that fluid loss plays an essential role in enhancing the acute antihypertensive action of captopril.…”