Hylenex Injection, Hyaluronidase Injection Enzyme 150 Unit Dose Single Vial (Rx) *Refrigerated Item*Hylenex Injection Hylenex is the brand name for a recombinant human hyaluronidase enzyme given by injection. Hyaluronidase is sometimes nicknamed a spreading factor because it helps make tissues more permeable, allowing fluids or medications injected under the skin to spread and be absorbed more easily. Normally, our connective tissue contains a gel like substance called hyaluronic acid that helps hold cells and fluids in place. Hylenex works by