Objectives: To determine the effects of potassium chloride 60 mmol/day supplementation on clinic and 24-h ambulatory blood pressure values in elderly untreated hypertensive patients.
Design: A double-blind randomized placebo-controlled crossover study lasting 8 weeks, following a 4-week run-in period.
Setting: Outpatient clinic in a district general hospital.
Patients: Eighteen untreated elderly hypertensive patients (mean age 75 years, range 66-79) with a systolic blood pressure of > or = 160 mmHg and/or a diastolic blood pressure of > or = 95 mmHg were recruited from the clinics of local general practitioners and from the current hospital outpatient department. Patients had not received any antihypertensive medication for at least 4 weeks before entry into the study.
Interventions: Before entry into the study, the daily dietary electrolyte intake of each individual was established and this was maintained during the run-in and intervention periods. Following a 4-week run-in period patients received potassium supplements or matching placebo, each for 4 weeks.
Main outcome measures: The within-patient changes in clinic and 24-h ambulatory blood pressures at the end of each intervention period.
Results: After 4 weeks potassium supplementation compared with placebo there was a significant fall in supine clinic blood pressure, standing and 24-h ambulatory systolic blood pressure. There was no significant change in clinic standing diastolic blood pressure, 24-h ambulatory diastolic blood pressure or pulse rate. Plasma renin activity increased and body weight fell after potassium supplementation. Twenty-four-hour urinary potassium rose significantly, whereas urinary sodium excretion was unchanged.
Conclusions: A 60-mmol daily supplement of potassium chloride reduces clinic and 24-h ambulatory blood pressure in elderly hypertensive patients.