Antimicrobial Use Guidelines (AMUG) version 21 - UW Health

APPENDIX G: Serum Drug Concentration Monitoring ProtocolUWHC Protocol For Inpatient Serum Drug Concentration Monitoring By Clinical PharmacistsProtocol developed by UWHC Center for Drug Policy (CDP)Author: Cindy Gaston, RPhCoordination: Lee Vermeulen, MS, RPh, FCCP, Director, CDPReviewed by: Pharmacokinetics CommitteeApproved By P&T: July 2001Last Reviewed: April 2007Next Scheduled Review Date: April 2009A. BackgroundThis protocol outlines the procedure of therapeutic monitoring of serum drug concentrations(SDC) by clinical pharmacists and gives the authority to the pharmacist to order serum drugconcentrations as necessary. Serum drug concentrations are useful to identify the causes ofunwanted or unexpected responses, improve clinical outcomes, and prevent unnecessarydiagnostic testing. Monitoring concentrations is important when pharmacologic and toxic effectscorrelate with SDC and therapeutic endpoints are difficult to assess clinically. Abnormalities inabsorption, distribution, or elimination can be detected by SDC monitoring. A serum drugconcentration may be necessary to evaluate an inadequate response to treatment, toxicity, andthe impact of drug interactions. However, SDC should not be the only means for determiningappropriate dose regimens. Accurate assessment and clinical judgment must be used to evaluateSDCs and determine appropriate dosing regimens.Timing of the SDC is important. Route of administration, dosage regimen, dosage form,pharmacokinetic characteristics of the drug, drug interactions, and alterations in elimination willdetermine the optimum time to obtain the serum sample. The drug should be allowed to distributethoroughly throughout the body before samples are obtained. Concentrations obtained during thedistributive phase are variable and do not correlate with the usual therapeutic range. To obtainthe most useful information SDC should be obtained at steady state. Steady state is reached in 4to 5 half-lives for drugs following first order kinetics. If a concentration is not at steady state, thenthe SDC does not reflect the drug’s clearance. It may be necessary to obtain a SDC beforesteady state if toxic or sub-therapeutic concentrations are a concern at that time. Impropersampling times can lead to misleading SDC and incorrect therapeutic adjustments.B. Policy and Procedure1.0 Policies1.1 Only SDC that can accurately and readily be measured and be correlated withtherapeutic or toxic effects will be ordered.1.2 The clinical pharmacist is responsible for reviewing each patient’s drug therapy andthe need for SDC, and if appropriate, ordering a serum drug concentration. Inadvance of ordering serum drug concentrations, the pharmacist will consider thetherapeutic goal of the specific medication.1.3 Indications for SDC include:1.3.1 Questionable drug efficacy1.3.2 Patient exhibiting signs of possible drug-related toxicity1.3.3 Noncompliance is suspected1.3.4 Concomitant disease states that can alter drug elimination1.3.5 Drug-drug interactions1.3.6 Establishing a baseline value after a patient exhibits a therapeuticresponse to drug therapy1.3.7 Changing dosage formulations or regimens