Medication adherence during laboratory workup for primary aldosteronism: pilot study

Purpose: Current hypertension guidelines stipulate that all incompatible medications be stopped before performing laboratory screening for aldosteronism, but patient adherence is unclear. We measured plasma drug concentrations to determine drug adherence and potential drug bias during biochemical tests. Patients and methods: Plasma concentrations of 10 antihypertensive drugs were quantified by mass spectrometry in 24 consecutive ambulatory patients with uncontrolled hypertension routinely evaluated for aldosteronism. Drug screening was done before (first visit), and on the day of biochemical tests (second visit) after stopping all incompatible medications. Concentrations above those expected at trough dosing interval defined same-day dose intake. Results: On the first and second visits, 76% vs 77% of prescribed antihypertensive doses could be verified in plasma. A total of 33% of patients were found to be nonadherent and showed divergent plasma drug results relative to prescriptions (21% drugs not detected/13% unprescribed drugs found) on first visit, 25% on the second (0%/25%), and 46% for both. A total of 21% used medication incompatible with the biochemical tests on the second visit. Moreover, 17% of drug concentrations were below expected trough levels on the first vs 15% on the second visit. This analysis revealed additional four (17%) vs three (13%) nonadherent patients who failed same-day dose intake and remained undetected by qualitative drug tests. Conclusion: Nonadherence was frequent during laboratory evaluations for aldosteronism advocating cautious interpretation of results. A multicenter study is desirable to set the stage for new screening protocols that should incorporate also incentives and checks of drug adherence.