Background The digoxin range conventionally used (0.8–2.0 ng/mL) may be suitable for patients with atrial fibrillation (AF), although a lower range is preferable for patients with congestive heart failure (CHF) (0.5–1.0 ng/mL).

Purpose To study if digoxin is monitored correctly and according to recent evidence.

Material and methods A retrospective study was conducted between January and June 2016. Field of study: two tertiary hospitals and their reference areas (the population consisted of 666 000 people). Adult patients with analytical determinations of digoxin during the study period were included. Digoxin concentrations were studied in blood samples of patients with CHF and/or AF. The percentage of patients with inappropriate levels of digoxin according to recent evidence was detected. Results were statistically interpreted. A descriptive analysis was conducted, followed by a χ² test to calculate the differences between all variables. The possible influence of age (younger or older than 75 years) and sex were also analysed.

Results A total of 102 analytical determinations in 95 patients were studied. 50% of the determinations in blood (51) showed inappropriate levels of digoxin. The number of inappropriate levels of digoxin was significantly higher in the group of patients >75 years of age (p=0.0481). However, no significant differences were found according to sex (p=0.903). 21.6% (22) of the analytical determinations showed blood digoxin levels above the range (>2 ng/mL for AF and >1 ng/mL for CHF). 28.4% (29) of patients had blood digoxin levels below the range (<0.8 ng/mL for AF and <0.5 ng/mL for CHF).

Conclusion The high number of determinations not within the range may indicate that in many cases healthcare professionals are not aware of the appropriate range of digoxin for each pathology. The elderly population had higher percentages of inappropriate blood digoxin concentrations, being more likely to have digoxin levels above the range. Thus therapeutic drug monitoring of digoxin in blood is not being used as often as it should, implying poor control of patients treated with digoxin.

No conflict of interest