Devices and methods for injecting or otherwise delivering multiple-component therapies to human or animal subjects. Devices having injectors (e.g., syringes) attached to biaxial or coaxial injection cannula(s) are used to deliver multiple components of a particular therapy such that those components become combined shortly before or upon exiting the injection cannula(s). In some embodiments, the injector devices of the present invention may include a first set of finger grips at a first location and a second set of finger grips at a second location. Also, in some embodiments, the injector devices of the present invention may include depth slops for controlling the depth within tissue at which the therapeutic substance is delivered. Also, in some embodiments, the injector devices of the present invention may include refill manifolds with attached syringes or other reservoirs containing the component substances to facilitate refilling of the injectors.