Mississippi Mud No More: Cost-Effectiveness of Pharmacokinetic Dosage Adjustment of Vancomycin to Prevent Nephrotoxicity

William Darko, Pharm.D., Joseph J. Medicis, Pharm.D., Adrienne Smith, Pharm.D., Roy Guharoy, Pharm.D., David F. Lehmann, M.D., Pharm.D.

Disclosures

Pharmacotherapy. 2003;23(5) 

In This Article

Results

Of the 200 patients who formed the reference case, 57 patients were in the concomitant nephrotoxin group, 68 in the intensive care group, and 78 in the oncology group. Three oncology patients were also in intensive care and were receiving concomitant nephrotoxins. Mean age and division of patients by age was consistent across the subpopulations. Pharmacokinetic monitoring and dosage adjustment resulted in less frequent trough concentrations exceeding 10 mg/L consistently across all populations and subpopulations. In the monitored group, 5.5% (57) of patients receiving concomitant nephro-toxins, 8.7% (68) of intensive care patients, and 3.0% (43) of oncology patients had vancomycin trough levels greater than 10 mg/L. In the nonmonitored control group, 18.4% (191) of patients receiving concomitant nephrotoxins, 23.6% (190) of intensive care patients, and 11.1% (148) of oncology service patients had vancomycin trough levels 10 mg/L or less.

The highest mean probability of nephrotoxicity found in the literature occurred in the subpopu-lation of patients receiving concomitant nephro-toxins, followed by oncology service patients, and a near equal probability in intensive care patients and combined (all) groups ( Table 3 ).[15,16,17,18,19,20,21] Table 4 shows the costs associated with therapeutic drug monitoring and nephrotoxicity, and Table 5 shows the results of the final cost-effectiveness analysis from the decision analysis (Figure 1). The mean cost of treating nephrotoxicity was $11,233. The mean cost of pharmacokinetic dosage adjustment and monitoring for all patients was $25,166 (sensitivity analysis $15,000-27,500)/nephrotoxic episode prevented. The subgroup analysis revealed a cost of $8363 (sensitivity analysis $4368-10,500)/nephrotoxic episode prevented for intensive care patients, a cost of $5000 (sensitivity analysis $1687-13,250) for oncology patients, and a dominant strategy with pharmacokinetic dosage adjustment and monitoring showing a cost savings of $5564 (sensitivity analysis $2724-12,428) for patients receiving concomitant nephrotoxins. The cost of preventing nephrotoxic episodes compared with the cost of managing these episodes is illustrated in Figure 2.

Decision analysis used to model the cost-effectiveness of pharmacokinetic dosage adjustment for vancomycin.

Comparison of the cost of preventing nephrotoxic episodes with the cost of managing these episodes. Vertical lines show the range of cost/nephrotoxic episode prevented. The perpendicular small marks on the vertical lines indicate the cost for the reference case; the arrow is the cost of treating one nephrotoxic episode.

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