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

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

Methods and Results: 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 to 6 weeks after hospitalisation with heart failure. 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 7 out of all 341 patients studied (2.1%) were completely non-adherent to all prescribed heart failure drugs. There were no major differences in baseline characteristics between adherent and non-adherent patients.

Conclusion: Non-adherence, assessed using a single spot urine measurement of drug levels, was confirmed in 1 of 5 patients evaluated 4 to 6 weeks after hospitalisation with heart failure.