Provider and pharmacist responses to warfarin drug-drug interaction alerts: a study of healthcare downstream of CPOE alerts.

OBJECTIVE: To categorize the appropriateness of provider and pharmacist responses to warfarin critical drug-drug interaction (cDDI) alerts, assess responses and actions to the cDDI, and determine the occurrence of warfarin adverse drug events (ADE) after alerts. DESIGN: An 18-month, retrospective study of acute care admissions at a single Veterans Affairs medical center using computerized provider order entry (CPOE). MEASUREMENTS: Patients included had at least one warfarin cDDI alert. Chart reviews included baseline laboratory values and demographics, provider actions, patient outcomes, and associated factors, including other interacting medications and number of simultaneously processed alerts. RESULTS: 137 admissions were included (133 unique patients). Amiodarone, vitamin E in a multivitamin, sulfamethoxazole, and levothyroxine accounted for 75% of warfarin cDDI. Provider responses were clinically appropriate in 19.7% of admissions and pharmacist responses were appropriate in 9.5% of admissions. There were 50 ADE (36.6% of admissions) with warfarin; 80% were rated as having no or mild clinical effect. An increased number of non-critical alerts at the time of the reference cDDI alert was the only variable associated with an inappropriate provider response (p=0.01). LIMITATIONS: This study was limited by being a retrospective review and the possibility of confounding variables, such as other interacting medications. CONCLUSION: The large number of CPOE alerts may lead to inappropriate responses by providers and pharmacists. The high rate of ADE suggests a need for improved medication management systems for patients on warfarin. This study highlights the possibility of alert fatigue contributing to the high prevalence of inappropriate alert over-ride text responses.

Determining vancomycin clearance in an overweight and obese population.

PURPOSE: Two methods of calculating vancomycin clearance were compared to determine the best body weight measure to use when dosing vancomycin for overweight and obese patients. METHODS: Hospitalized veterans weighing more than 120% of their ideal body weight (IBW) with serum vancomycin concentrations (SVCs) drawn between January 1, 2003, and June 30, 2005, were eligible for study inclusion. Exclusion criteria included weight of more than 300% the IBW, unstable renal function, dialysis, uncertain vancomycin dosing or sampling times, and distribution-phase sampling. Data from January 1 through December 31, 2003 (phase 1) determined the best-fit weight for vancomycin clearance for the Leonard and Boro method. The bias and precision of the modified Leonard and Boro method using the best-fit weight for vancomycin clearance were then compared with those of the Rushing and Ambrose method for predicting SVCs from January 1, 2004, through June 30, 2005 (phase 2). RESULTS: Forty-eight patients were included in phase 1, with 67 SVCs for analysis. During phase 1, adjusted body weight (ABW), using the Leonard and Boro method, was superior in predicting vancomycin clearance and the resultant SVCs. A total of 96 patients were included in phase 2 of the study, with 160 SVCs for analysis. The modified Leonard and Boro method was significantly more precise than the Rushing and Ambrose method in predicting vancomycin clearance. CONCLUSION: Use of ABW proved to be superior compared with total body weight when estimating vancomycin clearance in overweight and obese patients. While there was no difference in bias between methods, the modified Leonard and Boro method was significantly more precise than the Rushing and Ambrose method in predicting SVCs when dosing vancomycin for obese patients.

Comparing two predictive methods for determining serum vancomycin concentrations at a Veterans Affairs Medical Center.

PURPOSE: Two predictive methods for determining serum vancomycin concentrations (SVCs) at a Veterans Affairs medical center were compared. METHODS: The data for inpatients at the San Francisco Veterans Affairs Medical Center who received i.v. vancomycin and had vancomycin concentrations recorded in 2003 were included in this retrospective study. Creatinine clearance was estimated by the Cockcroft and Gault equation. Volume of distribution and creatinine clearance were calculated for each patient, using the Leonard and Boro method and the Rushing and Ambrose method. The Sheiner and Beal method for determining precision and bias was used to evaluate whether the two methods significantly differed in their ability to predict SVCs. RESULTS: Of the 223 patients identified, 122 patients were included, and 212 SVCs were analyzed. The population was mostly male and had a mean age of 64.1 years. There were no significant differences in 95% confidence intervals for relative precision and relative bias between the two methods. In patients whose weight was within 120% of their ideal body weight (IBW), the Leonard and Boro method was significantly more precise and less biased in predicting SVCs. In patients whose weight exceeded 120% of their IBW, the Rushing and Ambrose method was less biased and tended to be more precise, although the difference in precision was not significant. CONCLUSION: Both methods yielded similar predictability for SVCs in a veterans population. The Leonard and Boro method better predicted SVCs in patients weighing within 120% of their IBW, while the Rushing and Ambrose method appeared to be more appropriate for calculating vancomycin dosages in patients whose weight exceeded 120% of their IBW.

Clinical and economic outcomes of pharmacist recommendations in a Veterans Affairs medical center.

Pharmacist recommendations and their clinical and economic outcomes in a Veterans Affairs (VA) medical center were studied. The first 600 pharmacist recommendations that met study criteria were evaluated for type and frequency, rate of acceptance by physicians, potential benefit or harm, and economic consequences. The study site included inpatient and outpatient settings and a skilled-nursing facility. The most frequent types of pharmacist recommendations involved adjusting the dosage or frequency of administration and discontinuing a drug that was not indicated for the patient's medical problem. The rate of acceptance of the recommendations was 92%. The recommendations led to improved clinical outcomes in over 30% of cases in each setting and no change in over 40% of cases in each setting. Evaluators determined that patient harm was avoided by the recommendations in 90% of cases; patient harm was caused in less than 1% of cases. The overall mean cost avoidance per recommendation was $700, and the mean total cost avoidance for all 600 recommendations was $420,155. Pharmacist recommendations improved clinical outcomes and saved money at a VA medical center.