Urinary Prostaglandin as a Potential Predictive Marker for Thiazide-induced Hyponatremia

Thiazides and thiazide-like diuretics are one of the five major classes of antihypertensive drugs. They act by inhibiting the apical Na+-Cl- -cotransporter in the distal convoluted tubules of the kidneys. Thiazides and thiazide-like diuretics often cause adverse effects, importantly a drop in plasma sodium levels that is called thiazide-induced hyponatremia (TIH). Data suggest a crucial role of urinary PGE2 in water reabsorption. Since urinary PGE2 concentrations were higher in patients with TIH, quantification of urinary PGE2 prior and after thiazide initiation might allow identification of patients at risk for TIH, presenting PGE2 as a potential novel predictive marker for the development of TIH. This study is to investigate whether urinary PGE2 concentration at baseline (prior to thiazide initiation) is associated with the development of TIH within the first four weeks of treatment. Hospitalized and ambulatory patients in whom a thiazide or thiazide-like diuretic will be newly prescribed are screened for inclusion. The study procedure contains the screening and inclusion, visit 1 before thiazide initiation, visit 2 4 weeks (+/-7days) after thiazide initiation and a 3-months follow-up (visit 3). An additional visit (visit 2.1) will only be added in case of a dose change of the thiazide or thiazide-like diuretic (4 weeks +/- 7 days after the dose change). The 2 hours- challenge is optional if the patient agrees to additional testing.