Nutritional dose of magnesium in hypertensive patients on beta blockers lowers systolic blood pressure: a double-blind, cross-over study.


Wirell MP, Wester PO, Stegmayr BG




J Intern Med


OBJECTIVES. To evaluate if magnesium alters blood pressure in hypertensive patients treated with beta blockers and if such effect can be coupled to a change in potassium and magnesium levels in muscle, serum and urine. DESIGN. A randomized double-blind, cross- over study with magnesium and placebo taken orally, each for 8 weeks. SETTING. Outpatient clinic, University Hospital, Ume~a, Sweden. SUBJECTS. Thirty-nine patients aged 26-69 years with moderate essential hypertension, treated before entry and during the study with continuous, unchanged beta blockers completed the study. INTERVENTIONS. Random allocation to receive magnesium aspartate or placebo. Daily magnesium dose was 15 mmol (365 mg) distributed three times a day over 8 weeks. MAIN OUTCOME MEASURES. Blood pressure, serum, urine and muscle magnesium and potassium. Measurements performed at the start, after 8 and 16 weeks. RESULTS. Systolic supine and standing blood pressure significantly decreased when magnesium was supplemented following placebo but not when magnesium was given at start. When magnesium and placebo groups were independently compared there was no significant change in supine and standing systolic and diastolic pressure. Serum and urine magnesium and serum potassium were significantly higher after magnesium treatment, whilst no change was present in urine potassium or in muscle magnesium and potassium. CONCLUSIONS. This study showed that 15 mmol magnesium day-1 given to mild to moderate hypertensive patients treated with beta blockers could be the cause of a significant decrease in supine and standing systolic blood pressure.