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  • Impact of a Pharmacist-Initiated Therapeutic Drug Monitoring Consult Service: METHODS

This study was approved by the Research Ethics Board at The Hospital for Sick Children.

A chart review was conducted for patients treated between January 2003 and January 2004, which represented the 6 months before and the 6 months after removal of the pharmacist-initiated TDM consult service (on July 1, 2003). All children admitted to general surgery units who received gentamicin therapy and who were reported to have exceptional serum gentamicin concentrations were included in the study. The following data were collected: age, sex, diagnosis, indication for gentamicin therapy, gentamicin dose, duration of gentamicin therapy, serum creatinine concentration, and serum gentamicin concentration.

Assessment of Serum Gentamicin Concentrations

All patients received traditional q8h gentamicin dosing. Exceptional serum concentrations of this drug were defined as peak value outside the range 5 to 10 mg/L and trough value outside the range 0.6 to 2 mg/L, as stated in the institution’s standard of care. For each point of assessment, the dose administration times recorded in the medication administration record and the peak and trough concentrations recorded in each patient’s chart were used to calculate the gentamicin elimination rate constant and half-life. The extrapolated maximal concentration and ideal dose adjustment were then calculated for each serum gentamicin concentration pair (peak and trough) using the Sawchuk-Zaske Method. Measures of patient response were not included in the assessment of appropriateness. Apcalis Oral Jelly


The clinician’s actual response in terms of dose adjustment was compared with the ideal calculated response to determine appropriateness. A clinician’s response was considered appropriate if (1) a dose adjustment was unnecessary and no dose adjustment was initiated or (2) a dose adjustment was necessary and the revised regimen was correct. A clinician’s response was considered inappropriate if (1) a dose adjustment was necessary but no dose adjustment was initiated, (2) a dose adjustment was necessary but the dose adjustment performed was incorrect, or (3) a dose adjustment was unnecessary but a dose adjustment was completed.

To determine the appropriateness of the clinician’s plan for subsequent laboratory monitoring, the following data were collected: ordering of repeat determinations of serum gentamicin concentrations after dose adjustment, the appropriateness of timing of any dose adjustment, ordering of weekly determinations of trough gentamicin concentration and serum creatinine for courses of therapy longer than 7 days, and adjustment of antibiotics according to culture results. cialis 20 mg online

The institution’s standards of care with respect to gentamicin dosing and monitoring were published in the formulary, which was freely available to all medical, nursing, and pharmacy staff during the study period.

Statistical Analysis

The sample size was calculated on the basis of assumptions that 90% of the exceptional serum gentamicin concentrations monitored by a pharmacist- initiated TDM consult service would be assessed appropriately but only 75% of those monitored by physicians (after removal of the TDM consult service) would be assessed appropriately. A minimum sample size of 112 pairs of serum gentamicin determinations per group was deemed necessary to allow for a type I error rate of 0.05 and a type II error rate of 0.20 (power of 80%). Data collection was stopped before the calculated sample size was reached because an overwhelmingly significant difference was observed between the groups.

Differences observed before and after removal of the pharmacist-initiated TDM consult service were analyzed with either the x2 test or Fisher’s exact test (for sample size less than 30). Statistical analyses were performed using Statistical Package for Social Sciences for Windows (version 10.1; SPSS Inc, Chicago, Illinois). canadian cialis

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