J Med Assoc Thai 2009; 92 (11):1500

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Effect of Pharmacist Participation in the Health Care Team on Therapeutic Drug Monitoring Utilization for Antiepileptic Drugs
Ratanajamit C Mail, Kaewpibal P , Setthawacharavanich S , Faroongsarng D

Objective: To compare the proportions of appropriate TDM utilization regarding the indication, sampling
time, and application of the measured drug levels of antiepileptic drugs (AEDs) between the pre-intervention
period and pharmacist intervention period.

Material and Method:
The baseline evaluation and pharmacist intervention study of TDM use for phenytoin,
carbamazepine, or valproic acid were conducted at a medical teaching hospital in Southern Thailand. TDM
requests, interpretation and dosage adjustment recommendations were mainly responsible by residents. In the
intervention period, each of the three-step TDM process was assessed by the pharmacist for appropriateness
and a suggestion provided if necessary prior to a final recommendation made by the resident. The criteria for
appropriateness of TDM for AEDs were developed and validated by two neurologists. The present
study included 44 TDM tests (22 patients) during the baseline period and 43 tests (27 patients) during the
intervention period. The proportions of appropriate TDM utilization between the two periods were compared
using Chi-square test.

Results: In the baseline period, proportions of appropriately performed TDM were: indication (63.6%),
sampling time (47.7%), and application of drug levels (63.6%). Pharmacist intervention significantly
increased the proportions of appropriate indication (97.7%, p = 0.001), sampling time (79.1, p = 0.0023),
and applications (83.7%, p = 0.0293). There were 12 tests (27.3%) and 29 tests (67.4%) (p = 0.0001) during
the baseline and the intervention period, respectively, that met all 3 criteria of appropriate TDM use. Sixteen
requests without indication found in the baseline period was reduced to one in the intervention period, and
thus reduced the unnecessary cost by 90%. Of 59 steady-state drug levels, 34 (57.6%, p = 0.0005) significantly
correlated with clinical responses.

Conclusion: Pharmacist intervention significantly improved appropriateness of TDM use, and substantially
reduced unnecessary costs. Using a screening checklist including the indication, sampling time and data
needed for proper interpretation of the results can help improve the appropriateness of TDM utilization.

Keywords: Therapeutic drug monitoring, TDM, Pharmacist, Antiepileptic drugs, Phenytoin, Carbamazepine,
Valproic acid

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