Assessment of digoxin pharmacokinetic measurements in tertiary level hospital

Abstract

Background: Despite digoxin toxicity especially in elderly it is still used in clinical practice for heart failure or atrial fibrilation (1-3). Monitoring of digoxin serum concentrations is recommended to warrant successful therapy with digoxin (4). Objectives of the study were (i) to evaluate frequency of digoxin pharmacokinetic measurements and their appropriateness to recommended therapeutic interval; (ii) to analyse influence of risk factors on digoxin serum concentration (DSC). Methods: In this retrospective study, measurements of DSC in three years were analysed and compared with recommended therapeutic level. Concentrations below 1.0 nmol/ml were considered as “too low concentration”, in the range 1.0 – 2.6 nmol/ml – “therapeutic” and above 2.6 nmol/ml – “too high concentration”. Influence of patients’ gender and age on DSC was evaluated. Consumption of digoxin in hospital departments was calculated to evaluate frequency of DSC measurements. Results: There were analysed 123, 86 and 78 DSC in 2010, 2011 and 2012, respectively. A half of DSC was measured in patients who used digoxin at home, were hospitalized and medication was not prescribed further. Consumption of digoxin in hospital departments is presented in fig. 1. The majority of digoxin pharmacokinetic measurements were done in department T6: 43.5 % of all DSC in 2010 (1 DSC for 0.32 DDD/100 OBD), 58.3 % - in 2011 (1 DSC for 0.36 DDD/100 OBD) and 53.1 % - in 2012 (1 DSC for 0.42 DDD/100 OBD).DDD/100 OBD – defined daily doses in 100 occupied bed days; other – 13 departments in 2010, 14 departments in 2011, 17 departments in 2012. It was determined that “too low” concentrations were dominating in patients treated with digoxin at home (fig. 2) while approximately equal distribution of DSC was observed in patients treated in hospital (fig. 3). Female age was significantly higher than male at home (p = 0.002 in 2011 and p = 0.021 in 2012) and in hospital (p = 0.011 in 2010 ). Conclusions: Digoxin pharmacokinetic measurements were performed in one hospital department constantly, while measurements are rare in other departments. Less than half of DSC in patients treated with digoxin in hospital and below third of patients at home were in therapeutic range. Higher percentage of “too high” DSC was observed in older women.