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Moxonidine therapy useful option for primary aldosteronism screening
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In healthy, normotensive men, treatment with moxonidine therapy for 6 weeks resulted in a decrease in blood pressure without altering the aldosterone-to-renin ratio, minimizing the risk for false-positive results in screening for primary aldosteronism, according to findings from researchers in Australia.
“Currently, the most popular screening test for [primary aldosteronism] is the plasma aldosterone-to-renin ratio (ARR),” Ashraf H. Ahmed, MBBS, MSc, PhD, of the endocrine hypertension research center at the University of Queensland School of Medicine, and colleagues wrote. “Although considered the most reliable available screening approach, the ARR is not without false positives or negatives. ... Because most antihypertensive medications are known to affect the ARR, it is often necessary to withdraw such interfering agents to enable confident interpretation of results. ... The identification of additional medications that are free of appreciable effects on the ARR would therefore be very worthwhile.”
Ahmed and colleagues analyzed data from 20 healthy men without hypertension who received 0.2 mg moxonidine (Physiotens, Abbott) once daily for 1 week, followed by 0.4 mg daily for 5 weeks. Men provided fasting, mid-morning blood samples (seated) at baseline and 1 and 6 weeks. Researchers measured plasma aldosterone and cortisol by high-performance liquid chromatography-tandem mass spectrometry, as well as direct renin concentration, renin activity, cortisol, sodium, potassium and creatinine.
At both 1 and 6 weeks, levels of plasma aldosterone (baseline median, 134 pmol/L), direct renin concentration (median, 20 mU/L), renin activity (median, 2.2 ng/mL per hour) and ARR using either direct renin concentration (median, 8 mU/L) or renin activity (median, 73 ng/mL per hour) remained unchanged after moxonidine therapy, despite expected decreases in systolic and diastolic BP, according to the researchers. In addition, there were no changes in measurements for urinary potassium, sodium, aldosterone or cortisol at 1 and 6 weeks.
The study was limited by the small sample size and use of healthy volunteers with a normal baseline ARR, but the approach avoided potential confounding effects from other antihypertensive agents and restricted sodium intake, the researchers noted. Next steps include assessing the effects of moxonidine in patients with confirmed primary aldosteronism.
“Our current study was intended to be an ‘initial look,’” they wrote. “We deliberately chose normotensive, unmedicated subjects, as this approach avoided the potential confounding issues of antihypertensive medications. We anticipated that moxonidine might suppress renin and cause false positive and not negative results.” – by Regina Schaffer
Disclosure: The researchers report no relative financial disclosures.
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