Serum potassium levels predict blood pressure response to aldosterone antagonists in resistant hypertension

The objective of this study was to identify factors associated with the blood pressure (BP) response to spironolactone--aldosterone receptor antagonist as an add-on therapy in patients with resistant hypertension (HTN). We retrospectively reviewed the data of subjects with resistant HTN who were treated with add-on spironolactone in a large HTN clinic. A paired Student's t-test was used to assess the differences between the BP values before and during spironolactone administration, and multivariate analysis was used to assess the predictors of a satisfactory BP response (a decrease in systolic BP >10%). We analyzed the data of 48 hypertensive participants. The add-on spironolactone therapy had a significant BP-lowering effect in both systolic and diastolic BP values (P < 0.01 for both). Baseline serum potassium levels of <4.5 mEq l(-1) were associated with a satisfactory BP response (P < 0.01). Furthermore, every decrement of 1 mEq l(-1) of serum potassium was independently associated with a fivefold higher rate of achieving a satisfactory BP response to spironolactone therapy (P = 0.024). Additional factors independently associated with an improved systolic BP response were old age (P = 0.033), body mass index (P = 0.033) and high baseline systolic BP (P=0.004). Our results support the use of add-on spironolactone therapy in patients with resistant HTN who are elderly and obese and have high systolic BP and serum potassium levels <4.5 mEq l(-1).