Hyponatremia caused by thiazide diuretics: be aware of drug combinations which enhance this effect

In 3 patients, two women aged 88 and 82 and a man aged 76, the consciousness became disrupted due to a severe hyponatraemia, after a thiazide diuretic had been combined with another drug without laboratory control. After a change in medication, the laboratory values and the patients' conditions normalised. Severe hyponatraemia is a well known but rare complication of thiazide therapy. It has a significant mortality and morbidity rate. The risk is greater for elderly women. This effect on serum sodium can be enhanced by the use of other drugs like furosemide, carbamazepine, paroxetine and NSAIDs. That a patient uses a thiazide is sometimes overlooked when a combined preparation of other drugs is prescribed. Diuretic serum electrolytes should be monitored once treatment with thiazide has been started, especially in elderly patients taking other drugs.