Via practica 1/2024

Pharmacokinetic changes in obese patients General overview and presentation of the working group of the Czech Professional Society of Clinical Pharmacy

Obesity is related to changes in pharmacokinetic parameters and blood levels of administered drugs, which can significantly complicate the pharmacotherapy of obese patients. An increase in the volume of distribution is generally expected, but due to a relative increase in the amount of fat mass compared to the hydrophilic compartment, this change is not always directly proportional to the increase in total body weight. The elimination organs may also be affected by obesity, leading to changes in drug clearance. Simply increasing doses according to total body weight could lead to overdose in many patients, whereas fixed doses may be associated with insufficient therapeutic effect. However, changes in body composition and elimination are not consistent for different drugs. Therefore, an unambiguous recommendation for dose adjustment of all drugs cannot be made. Drug dosing after bariatric surgery presents a unique challenge, when it is necessary to assess changes in bioavailability and their gradual adjustment over time from the procedure, as well as dramatic weight reduction requiring regular reassessment of pharmacotherapy. Although obesity is a growing problem worldwide, we still face an insufficient amount of reliable data and clinical studies dealing with drug dosing in obese patients. Based on the available information, this article describes the basic principles of dosing in obesity.

Keywords: bariatric surgery, BMI, clearance, obesity, volume of distribution