Pharmacokinetics in Obese Patients: Drug Absorption and Distribution

Obese individuals typically have more fat tissue and less lean tissue, which impacts drug absorption and distribution. However, available data are limited.

For example, the bioavailability of metformin was compared between individuals who underwent gastric bypass surgery and those who did not, with both groups having a similar BMI.

The results showed a 50% increase in metformin bioavailability after gastric bypass surgery compared to the nonsurgery cohort.

Drug distribution in obese individuals is affected by increased adipose tissue and the drugs’ lipophilicity.

For instance, lipophilic drugs show an increased V_D and prolonged half-life compared to hydrophilic drugs, which exhibit a lesser V_D.

However, certain lipophilic drugs, such as cyclosporine, have a lower V_D in obese patients than in non-obese patients.

Additionally, obesity can alter the concentrations of plasma proteins such as α₁-acid glycoprotein, affecting the unbound drug fraction. For instance, an increase in protein concentration can decrease the unbound drug concentration.