Should We Routinely Measure Renin Levels to Diagnose and Treat Patients With Hypertension? (Part I)

The Argument For

Phyllis August, MD, MPH

In This Article

Measuring Renin in Patients Already on Therapy

More common than the newly diagnosed, untreated patient with hypertension is the individual on therapy with inadequately treated hypertension. In such cases the physician must decide whether to increase the medication that the patient is already taking, add a second or third drug, or stop the current medication and switch to another medication. If the clinical history is not helpful (e.g., there is no documentation of the efficacy of drug "A"), then measuring a renin level (either plasma renin activity or direct renin) can be helpful, provided the known effects of various drugs on renin levels are taken into consideration. For example, an individual with uncomplicated essential hypertension is taking lisinopril 40 mg daily and has a BP of 160/95 mm Hg. Measuring a plasma renin level can guide your response in this situation. If the renin level is very low, then it is unlikely that the lisinopril is having much of a therapeutic effect, since patients with a reactive renin system should have an increased renin while on ACE inhibitor therapy. A reasonable strategy would be to stop the ACE inhibitor and start a diuretic. If the renin level is high, then it might be reasonable to add either a ß blocker or an angiotensin receptor antagonist. Similarly, if a patient taking a diuretic still has elevated BP and the renin level is high, then an ACE inhibitor or angiotensin receptor blocker should be considered. If the renin level is low while on a diuretic, then an aldosterone antagonist could be considered.