Publication:

A comparative analysis of hydrochlorothiazide and chlorthalidone induced hyponatremia at the dose commonly prescribed in clinical practice

Background Despite the differences in cardiovascular outcomes, pharmacokinetics, pharmacodynamics, the diuretics, chlorthalidone (CTD) and hydrochlorothiazide (HCTZ) are often considered as interchangeable. There is an on-going debate whether CTD should be preferred over HCTZ, because it appears to be more effective in the prevention of cardiovascular events. The relative difference in the incidence of hypokalemia and hyponatremia, is also a topic of debate. With this background, the study was carried out to compare the prevalence of hyponatremia between CTD and HCTZ used in the treatment of hypertension at the dose commonly prescribed in clinical practice.

Methods This was a cross sectional study carried out on a convenience sample of 74 adult patients with provisional diagnosis of hyponatremia or with a plasma sodium level of less than 135mmol/L and having a history of anti-hypertensive use of HTCZ or CTD in the dose range of 12.5-25mg/day and 6.25-12.5mg/day respectively. Chi square test and independent samples ‘t’ test were used analyse the results in GraphPad Prism 6.0.

Results HCTZ was found to be the preferred diuretic in hypertension, whereas CTD was preferred in the age group of 65-74 years. The symptoms indicative of hyponatremia as well as a lower plasma sodium level were more common in the HTCZ treated group. Patients of hypertension using CTD were less predisposed to hyponatremia (OR 0.804, 95% CI 0.207-3.12).

Conclusions Chlorthalidone, when used at a lower dose of 6.25-12.5mg/day for the treatment of hypertension cause a lesser risk of hyponatremia than hydrochlorothiazide.