The Impact of Weight on Drug Dosing

The Impact of Weight on Drug Dosing
The Impact of Weight on Drug Dosing
MPR reports on the impacts of elevated body mass index (BMI) on drug dosing.

According to the Centers for Disease Control and Prevention (CDC), more than one-third of Americans are considered obese, and nearly 70% of the U.S. population is considered overweight.1,2 Obesity-related conditions, including cardiovascular disease, stroke, type 2 diabetes, and certain types of cancer, are the leading causes of preventable death.1

With the incidence and prevalence of obesity climbing as well as these resulting conditions, there is uncertainty about how to dose certain medications to treat obesity-related and non-obesity-related conditions. Specifically, prescribing appropriate doses of medications that require weight-based calculations, such as opioids, anticoagulants, thrombolytics, anti-infectives, cardiac agents, corticosteroids, anticonvulsants, neuromuscular blocking agents, and sedatives, can be very challenging in terms of effectiveness and adverse events.

The Impacts of Being Overweight or Obese on Drug Dosing

In an effort to understand how to dose drugs for these patients so they gain benefit from treatment and do not experience any unnecessary adverse events, Sandra L. Kane-Gill, PharmD, of the University of Pittsburgh School of Pharmacy in PA, and colleagues evaluated dose ranges of high-risk medications administered by continuous infusion requiring weight-based dosing in overweight and obese patients. In this prospective, multicenter, observational study, the investigators evaluated 857 medication orders representing 11 different high-risk medications in 173 patients. There were six vasoactive agents evaluated including dobutamine, dopamine, milrinone, nitroglycerin, norepinephrine, and phenylephrine. The other five high risk medications assessed included heparin, three sedatives (fentanyl, midazolam, and propofol) and one neuromuscular blocker (rocuronium). 2

Nearly One-Third of the World is Overweight

“In this study, we were able to review the drugs at three institutions and despite our efforts in getting a sufficient number of patients, we weren’t able to come to any definitive conclusions on to how to dose these patients,” said Kane-Gill.

In this study, the investigators found that 9 of 14 patients who experienced adverse events were obese or overweight, meaning drug dosing in this population is a concern. In addition, a large number of doses were discontinued due to inefficacy for overweight and obese patients confirming the uncertainty in dose selection.2 Therefore, according to Kane-Gill, more data on how to best dose these individuals are necessary.

“We believe that we need a multicenter registry to document how patients are being dosed and what are the outcomes for individuals. This will provide us with a better understanding of drug dosing in overweight and obese patients and will better guide our future decisions,” said Kane-Gill.