ABSTRACT
The utilization of therapeutic drug monitoring [TDM] for serum digoxin and theophylline was assessed with respect to the indication, time of sample collection and contribution to patient care. A total of 585 serum drug level determinations of digoxin [275] and theophylline [328] were done in a four month period. Reasons for requests were subtherapeutic response [27.5%], suspected toxicity [3.8%], baseline data [26.7%], patients at risk for toxicity [7.7%], and for the remaining 34.4% of orders, no reason was stated. The highest number of requests 246 [42.1%] were from the inpatient ward [INP], followed by emergency room [ER] 32.6%, outpatient department [OPD] 13% and intensive care unit [ICU] 12.3%. Repeated assays accounted for 363 determinations of which 55.9% had levels similar to the previous ones. In this study, we found a high incidence of inappropriateness in patient selection [34.4%], time of serum sample collection [28.4%], and dosage adjustment [46.8%]. However, when these audit criteria were analyzed together, the overall appropriateness was as low as 33.5%. This indicated that serum drug monitoring was poorly utilized and did not contribute much to the patient's care. This results in an estimated financial loss per year [for inappropriate use of digoxin and theophylline levels] of about 37,344 Saudi Riyals [US $ 9,956.00]. Corrective educational programs for the staff, based on standard guidelines for TDM, have been initiated and this study is a baseline for future prospective audits