EVALUATION OF SERUM DRUG CONCENTRATIONS IN A TERTIARY CARE HOSPITAL: A CROSS-SECTIONAL STUDY

Background: Serum drug concentration (SDC) is an important parameter used in drug efficacy and treatment follow-up. Aim: This study aimed to evaluate subtherapeutic, therapeutic and toxic SDCs, SDC measurement requests and demographic specialities (age and sex) for carbamazepine, phenytoin, phenobarbital, lithium and digoxin. Materials and Methods: This is a cross-sectional study, evaluating the outpatients' and inpatients' SDC data treated at Research and Application Hospital of Afyonkarahisar Health Sciences University between January 1, 2012 and February 28, 2019, and having SDC data. The relations between dependent and independent variables was evaluated with chi-square analysis and Students' T -test. P<0.05 was considered statistically significant. Results: A total of 3735 patients, 8946 admissions (mean: 41.1 +/- 26.6 years, 51.3% females) and 10158 SDCs were reviewed. Digoxin SDC was the most common measurement, at a rate of 33.7%. The highest number of SDC measurement was made in 2016 (n=1627). Subtherapeutic SDC rates were high for phenytoin, lithium, and digoxin (69.8%, 39.7%, 35.8%, respectively). Digoxin (16.2%) and phenobarbital (9.8%) were the drugs with the highest rate of toxic SDC. SDC increased for all drugs with increasing age, this was statistically significant for carbamazepine, lithium and digoxin (P<0.05). SDC for digoxin was found to be significantly higher in female sex (P<0.001). Conclusion: In this study, subtherapeutic and toxic SDC levels were examined. This study revealed the need for prospective studies evaluating Therapeutic Drug Monitoring (TDM) together with patient- and drug -related factors.