A Real‐World, Multicenter Assessment of Drugs Requiring Weight‐Based Calculations in Overweight, Adult Critically Ill Patients

Abstract

Prescribing appropriate doses of drugs requiring weight-based dosing is challenging in overweight patients due to a lack of data. With 68% of the US population considered overweight and these patients being at an increased risk for hospitalization, clinicians need guidance on dosing weight-based drugs. The purpose of this study was to identify “real-world” dose ranges of high-risk medications administered via continuous infusion requiring weight-based dosing and determine the reasons for dosing changes (ineffectiveness or adverse drug reactions). A prospective, multicenter, observational study was conducted in four intensive care units at three institutions. A total of 857 medication orders representing 11 different high-risk medications in 173 patients were reviewed. It was noted that dosing did not increase in proportion to weight classification. Overall, 14 adverse drug reactions occurred in nine patients with more in overweight patients (9 of 14). A total of 75% of orders were discontinued due to ineffectiveness in groups with higher body mass indexes. Ineffectiveness leads to dosing adjustments resulting in the opportunity for medication errors. Also, the frequent dosing changes further demonstrate our lack of knowledge of appropriate dosing for this population. Given the medications' increased propensity to cause harm, institutions should aggressively monitor these medications in overweight patients.

Continuing to Challenge Practice to Be Evidence Based

“…24,27 Two populations at greatest risk of inaccurate weightbased medication dosing are elderly patients and obese patients. 24,[27][28][29][30] Elderly patients are at risk of adverse drug reactions most frequently because of changes in renal function, 29 and obese patients are at increased risk because of limited data guiding correct dosing in this population. 24,26,27,30 Dosages for patients who are overweight are more likely to be too high or too low.…”

“…24,[27][28][29][30] Elderly patients are at risk of adverse drug reactions most frequently because of changes in renal function, 29 and obese patients are at increased risk because of limited data guiding correct dosing in this population. 24,26,27,30 Dosages for patients who are overweight are more likely to be too high or too low. Correct dosing in overweight patients is a concern because 68% of adults are overweight or obese, 6.7% are morbidly obese, 31 and overweight individuals have a high number of hospital admissions, longer duration of mechanical ventilation, and longer hospital stays.…”

“…Thus use of BMI as a standard metric for determining weightbased medication dosing should be avoided. 24,27,37 However, knowing a patient's BMI, specifically if they are in the obese (BMI 30-39.9) or extremely obese (BMI >40) categories, may be helpful in determining weight-based dosing. In a multicenter randomized cohort study 37 evaluating the therapeutic effectiveness of vancomycin dosing, researchers reported that incorporating BMI was an important factor to consider as higher dosing was needed in patients who were obese to achieve therapeutic blood levels of the agent.…”

“…24,26,36 Using an obese patient's ABW to calculate a medication dosage will on average result in too high a dose, and using an obese patient's IBW will on average result in a subtherapeutic dose for the patient. 27,38 Dry weight is often a misused phrase in the ICU. Nurses may consider a patient's admission weight to be the person's dry weight; this is incorrect.…”

“…Kane-Gill and colleagues 27 conducted an observational study of "real world" dosing and adverse drug reactions. The researchers reported that most adverse drug reactions occurred in overweight patients.…”