Appropriateness of Therapeutic Drug Monitoring Request of Valproic Acid for Inpatient and Emergency Department Patients in Sibu Hospital

Abstract

Introduction:

Therapeutic drug monitoring (TDM) refers to the individualisation of dosage by maintaining plasma or serum drug concentrations within a target range. The World Health Organisation (WHO) proposed categorising valproic acid (VPA) to be of lower priority among the listed drugs for TDM. However, VPA is one of the most commonly analysed assays in Sibu Hospital. This study aimed to evaluate the appropriateness of therapeutic monitoring of VPA in Sibu Hospital. The results from this study will help to better understand the various indications for VPA sampling in the hope to reduce unnecessary VPA TDM requests in the future.

Methods:

This was a retrospective cross-sectional clinical audit that included the VPA TDM requests for inpatient and emergency department patients in Sibu Hospital. Data were retrieved from VPA TDM forms from 1st January to 31st December 2020 and case notes. The collected data included demographic characteristics, antiepileptic drug (AED) information, indications and sampling time of VPA TDM requests, pharmacist’s recommendation, and prescriber’s acceptance, which were then analysed using SPSS version 22.

Results:

A total of 97 VPA TDM requests for 61 patients were included in the clinical audit. The majority (90.7%) of the requests came with appropriate indications and almost half of the VPA TDM samples were taken at the appropriate timing. Pharmacists proposed dose increments for half of the requests with subtherapeutic drug levels. Around three quarters (72.2%) of pharmacists’ recommendations were accepted by prescribers.

Conclusion:

We concluded that the majority of VPA TDM requests had appropriate indications. Unfortunately, half of these requests were sampled incorrectly, limiting valuable recommendations on dose adjustments. Measures should be taken to ensure VPA TDM are ordered with appropriate indications and accurate sampling time in order to optimise the service.