Drugs with monoclonal antibodies (mAb) represent an important group of therapeutics in both development and on the market due to their high specificity and efficacy. More and more of them are available for subcutaneous (SC) application, since they represent numerous advantages for patients. SC application dictates the use of highly concentrated mAb formulations, which increase the viscosity of the formulations and lead to higher necessary injection forces and the occurrence of pain in patients. The reduction of injection force, despite the high viscosity of the formulations, can be influenced by the appropriate choice of needle and syringe used for application. In the master's thesis, we studied the influence of mAb concentration on the viscosity of formulations. The mAb concentration of the formulations was determined using a spectrophotometry method and the viscosity was measured using a viscometer-rheometer on a chip. The viscosity of the formulations increases with increasing mAb concentration due to shorter distance between molecules and more intermolecular interactions between them. We developed and optimized a method for measuring the injection force of liquids with different viscosities on the TA.XTplusC texture analyzer. As part of method optimization, we demonstrated that the method gives repeatable results by calculating the relative standard deviation. For the purposes of developing a method for measuring the injection force, we first checked the influence of sucrose concentration on the viscosity of the aqueous solution and demonstrated a trend of increasing viscosity with increasing sucrose concentration. When optimizing measurements on the texture analyzer, we studied the influence of the viscosity of aqueous sucrose solutions, the size of the syringe and the size of the needle diameter on the injection force. With increasing sucrose viscosity, the injection force of the aqueous solution increased. We also found that the smaller the inner diameter of the needle, the higher the injection force required. We explained this by considering the Hagen-Poiseuille law, which states that the injection force directly depends on the resistance of the fluid to flow. The resistance of fluid to flow through the syringe and needle is smaller when the fluid viscosity is lower and the needle diameter is larger. Afterward, when evaluating the injection force of formulations with mAb, we concluded the same as with aqueous sucrose solutions, namely that with increasing mAb concentration, the injection force also increases, in some formulations even beyond the upper limit for appropriate SC administration.
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