Evolution of Therapeutic Drug Monitoring requests in a tertiary University Hospital in the last 16 years

ABSTRACT

Introduction: TDM has been widely used in clinical practice for many years and has application in various groups of drugs,mainly in drugs with pharmacokinetic variability, concentration related therapeutic and adverse effects, narrow therapeutic index, defined therapeutic concentration range and desired therapeutic effect difficult to monitor. Objectives: The aim of this study is to assess the evolution of TDM application throughout the years and its usefulness and necessity nowadays in a tertiary University Hospital. Methods: Data of Therapeutic Drug Monitoring requests were collected for the years 2005, 2010, 2015, 2019, 2020 and 2021 from the records of the Laboratory of Pharmacology General University Hospital of Alexandroupolis. Drugs monitored included digoxin, valproic acid, carbamazepine, phenytoin, phenobarbital, cyclosporine, tacrolimus, amikacin, gentamycin, vancomycin, serum benzodiazepines, methotrexate, cortisol, acetaminophen, salicylate, theophylline, tobramycin and primidone. More specifically, the data collected were the drug's level measurement and the clinic that requested the specific drug order. Results: A total of 1357 drug level measurement records were found for 2005, 1442 for 2010, 766 for 2015, 520 for 2019, 442 for 2020 and 622 for 2021. During these years the most frequent drug requested for TDM was digoxin (2005), cyclosporine (2010, 2019), valproic acid (2015, 2020), and tacrolimus (2021). In regards to the drugs requested, digoxin was predominantly requested by Cardiology and Pathology, cyclosporine and tacrolimus by Nephrology and valproic acid by Psychiatry. Furthermore, the percentage of non optimal therapeutic levels that required dose adjustments were calculated and will be presented. Conclusion: TDM retains a degree of its value as shown by the number of incidents requiring dose modifications. In addition, the presented results obtained from 2005 to 2021 show that there is a notable decrease in the number of requests for TDM per year. This can be imputed to several reasons such as the replacement of specific drugs with new therapeutic regimens and the evolution of therapeutic drug protocols in several diseases. Another major factor was the measures taken against the Covid-19 pandemic in the last two years which resulted to a substantial decrease of routine health examinations and scheduled appointments in the Hospital.