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There is a wide variety of diuretic-induced metabolic abnormalities of unequal severity. Renal failure can be caused by excessive sodium loss, or by certain drug combinations comprising, for instance, a nonsteroidal anti-inflammatory drug (NSAID) or an ACE inhibitor. Hyponatraemia is uncommon. It is encountered with thiazides, especially among women. A sodium level less than 120 mmol/L may result in neurological complications. Hypokalaemia is frequent and might increase the risk of cardiac arrhythmia. Hyperkalaemia induced by potassium-sparing diuretics is often combined with another contributive cause. Glucidic, lipidic and uric acid abnormalities are common, but their clinical effects are slight. They do not seem to worsen cardiovascular risks among elderly patients. Nevertheless, prescribing diuretics for elderly patients requires special precautions. Reducing the diuretic dose, as is now recommended for treating hypertension, seems to lessen adverse effects, and despite all the adverse reactions just mentioned, it has been proven that diuretics are beneficial in many diseases.

In order to assess the responsibility of medicinal drugs for the disorders in electrolytes observed in elderly people, the prevalence of abnormal natraemia and kalaemia was prospectively established in 631 subjects aged 70 or more on the first day of hospitalization. Among 337 subjects not taking drugs likely to create problems (diuretics, angiotensin-converting enzyme inhibitors, anti-inflammatory agents) 3.6 percent had hyponatraemia (below 130 mmol/l) and 12.2 percent had hypokalaemia (below 3.5 mmol/l). Subjects with normal renal function who were taking angiotensin-converting enzyme inhibitors or non-steroidal anti-inflammatory agents showed no more electrolytic abnormalities than those who did not take them. Conversely, subjects on thiazides were more frequently hyponatraemic (11.8 percent) or hypokalaemic (16.2 percent; 20 percent in the absence of associated distal diuretics). These abnormalities were more frequent in women than in men (21.7 and 13 percent). This, together with the fact that 68 percent of subjects taking thiazides were women accounts for the marked female predominance of electrolytic abnormalities reported in the literature.