English abstract
Aim: To evaluate prospectively the appropriateness of sampling time and indications of therapeutic drug monitoring (TDM) requests at Sultan Qaboos University Hospital (SQUH).
Methods: All in-patients TDM requests reaching biochemistry laboratory at SQUH in the period from October 2013 to January 2014 were evaluated. The evaluated drug's requests were carbamazepine, phenytoin, phenobarbital, valporic acid, digoxin, gentamycin, amikacin, vancomycin, tobramycin, theophylline, lithium, and cyclosporine. Criteria for appropriate indications and sampling time were developed from literature and adapted according to SQUH guidelines. Data was presented as descriptive and analyzed using SPSS program,
Results: Seven hundred and thirty three TDM requisitions were evaluated, majority of which were for antibiotics (75%) followed by antiepileptics (10.5%) and cyclosporine (8.9%). There were 53.89% male and 51.15% of requests were for patients <18 years of age. Of the TDM results, 42.3%, 41.2%, and 16.5% had plasma concentrations within, below and above the reference range, respectively. Most of the requests had appropriate indication (78.2%) of which most were indicated for initial monitoring. Only 28.5% had appropriate sampling time. TDM results were applied by dosage adjustments in 65.75% of requests. Based on the indication, sampling time and application of results, only 12.96% of requests could be labeled as appropriate utilization of TDM service.
Conclusion: In conclusion, the study showed that most of the TDM requests were indicated appropriately but less number with appropriate sampling time. Physicians were mostly applying the results when plasma concentrations were above the therapeutic range. Considering our data, TDM service is much less than optimal at SQUH. Clinical pharmacists could participate in the service by providing educational materials and sessions to hospital personnel regarding sample collection times of different drugs, interpretation of results, indications and proper use of TDM service.
