Drug pharmacokinetics in the obese population: challenging common assumptions on predictors of obesity-related parameter changes

Abstract

Introduction:Obesity is associated with many physiological changes. We review available evidence regarding five commonly accepted assumptions to a priori predict the impact of obesity on drug pharmacokinetics (PK). Areas covered: The investigated assumptions are: 1) lean body weight is the preferred descriptor of clearance and dose adjustments; 2) volume of distribution increases for lipophilic, but not for hydrophilic drugs; 3) CYP-3A4 activity is suppressed and UGT activity is increased, implying decreased and increased dose requirements for substrates of these enzyme systems, respectively; 4) glomerular filtration rate is enhanced, necessitating higher doses for drugs cleared through glomerular filtration; 5) drug dosing information from obese adults can be extrapolated to obese adolescents. Expert opinion: Available literature contradicts, or at least limits the generalizability, of all five assumptions. Clinical studies should focus on quantifying the impact of duration and severity of obesity on drug PK in adults and adolescents, and also include oral bioavailability and pharmacodynamics in these studies. Physiologically based PK approaches can be used to predict PK changes for individual drugs but can also be used to define in general terms based on patient characteristics and drug properties, when certain assumptions can or cannot be expected to be systematically accurate.

Inclusion of Obese Participants in Drug Development: Reflections on the Current Landscape and a Call for Action

“…However, until sufficient verification of PBPK modeling in obese subjects has been performed and confidence is sufficiently high in prospective predictions, PBPK modeling could be used to support initial dose estimates for clinical trials and also systematically elucidate the impact of key parameters among the (patho)physiological changes, drug properties, and longitudinal changes, which all interact with each other. 16,17 Any translational or clinical characterization of the effects of obesity on the PK of an investigational agent in development should be coupled with an assessment of anticipated clinical impact. This reinforces the critical importance of characterizing the exposure-response relationships for efficacy and safety throughout drug development.…”

“…Application of these models in an obese population has received increasing attention over the past few years due to their mechanistic nature. However, until sufficient verification of PBPK modeling in obese subjects has been performed and confidence is sufficiently high in prospective predictions, PBPK modeling could be used to support initial dose estimates for clinical trials and also systematically elucidate the impact of key parameters among the (patho)physiological changes, drug properties, and longitudinal changes, which all interact with each other 16,17 …”

Identifying Phenotypic Determinants of Infliximab Target Concentrations in Inflammatory Bowel Disease: Toward Personalized Evidence-Based Dosing Regimens

“…This applies not only to clinical practice but also when designing clinical trials. Some studies have shown that proactively measuring infliximab trough levels and adjusting the dose independently of disease activity may not offer a benefit over conventional therapy (4,5). Those studies used infliximab concentrations that have historically been considered to correlate with better efficacy but perhaps the standardization of the goal drug concentration cannot really be applied to the entire population.…”

“…In these analyses, it is crucial to use a data-driven approach that avoids preconceived notions. It could consider multiple size descriptors, in conjunction with other patient and treatment characteristics, using both linear and nonlinear functions (4).…”

Is There a Need for a Dedicated Pharmacokinetic Trial for a Drug in Obese Populations? A Drug Prioritization Decision Tree Framework

“…8,21 As a result, the Vd is typically larger compared with less lipophilic drugs; however, there is wide variation. 8,18,21,22 Obesity can also alter the pharmacokinetics of lipophilic drugs through their accumulation in adipose tissue. 21 This increased Vd of lipophilic drugs in people with obesity can decrease the initial/maximum concentration of a drug.…”