a method for transferring and mixing a pharmaceutical mixture utilizing a by - pass cartridge and a syringe . after mixing the dry component and the diluent in the by - pass cartridge , the mixture can be passed to a syringe which includes a syringe plunger having a fluid passageway therein with a hydrophobic membrane covering the passageway . the mixture can be transferred back and forth between the by - pass cartridge and the syringe through a small bore to achieve mixing , particularly in the case of microspheres held in suspension .