Development of hospital pharmacy practice using therapeutic drug monitoring

Abstract

Therapeutic drug monitoring (TDM) is a developing field in hospital pharmacy that contributes to good clinical response. Optimal concentrations of immunosuppressants, anti-epileptic drugs, and glycopeptide antibiotics are narrow, and these drugs are widely monitored by fluorescence polarization immunoassay (FPIA) in clinical settings. Recently, a chemiluminescence immunoassay (CLIA) has also become available. We compared these two assays in monitoring serum concentrations of cyclosporin A (CsA), carbamazepine (CBZ), phenobarbital, phenytoin, and valproic acid. FPIA estimates of CsA and CBZ concentrations were higher than CLIA estimates. We also evaluated the two methods' cross-reactions to metabolites. The FPIA, but not the CLIA, method was affected by metabolites. We conclude that CLIA has adequate precision and accuracy for use in routine therapeutic drug monitoring in clinical situations. We also report a case of meningitis caused by methicillin-resistant Staphylococcus epidermidis (MRSE) in a neonatal girl. The patient had intraventricular hemorrhage and was treated with ventricular drainage. Because MRSE was detected in her cerebrospinal fluid (CSF), vancomycin (VCM) was administered intravenously, but had no beneficial effect. Subsequent treatment with linezolid (LZD) successfully ameliorated her CSF cell count and protein levels. These results indicate that LZD may be a treatment option for neonates and infants for drain-associated meningitis caused by MRSE. In conclusion, TDM can determine drug concentration and indicate optimal pharmaceutical approach for treatment.