Adherence to prescribed medications in patients with heart failure: insights from liquid chromatography–tandem mass spectrometry-based urine analysis

None of the existing studies on adherence have directly measured levels of all medications (or their metabolites) in patients with heart failure (HF).

We used liquid chromatography–tandem mass spectrometry to measure the presence of prescribed drugs (diuretics, angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, beta-blockers, and mineralocorticoid receptor antagonists) in the urine of patients reviewed 4–6 weeks after hospitalization with HF. Patients were unaware that adherence was being assessed. Of the 341 patients studied, 281 (82.4%) were adherent, i.e. had all prescribed drugs of interest detectable in their urine. Conversely, 60 patients (17.6%) were partially or completely non-adherent. Notably, 24 of the 60 were non-adherent to only diuretic therapy and only seven out of all 341 patients studied (2.1%) were completely non-adherent to all prescribed HF drugs. There were no major differences in baseline characteristics between adherent and non-adherent patients.

Non-adherence, assessed using a single spot urine measurement of drug levels, was confirmed in one of five patients evaluated 4–6 weeks after hospitalization with HF.