Subcutaneous Absorption of Monoclonal Antibodies: Role of Dose, Site of Injection, and Injection Volume on Rituximab Pharmacokinetics in Rats

To determine the effect of dose, the anatomical site of injection, and the injection volume on subcutaneous absorption of rituximab in rats and to explore absorption mechanisms using pharmacokinetic modeling.
Rituximab serum concentrations were measured following intravenous and subcutaneous administration at the back, abdomen, and foot of rats. Several pharmacokinetic models were developed that included linear and saturableabsorption, and degradation and/or protective binding at the injection site.