An injector includes a needle movable from a retracted position to an injection position. A rotary biasing assembly is stabilized in a stored energy state and releasable into an energy releasing state and includes a cam. A cam follower couples the rotary biasing assembly with the needle and is configured to transform rotation of the rotary biasing assembly in the energy releasing state thereof into translation of the needle from the retracted position to the injection position. An activation switch is rotatable from an unactivated position, stabilizing the rotary biasing assembly in the stored energy state thereof, to an activated position, releasing the rotary biasing assembly into the energy releasing state thereof. An activation button is movably mounted to the injector housing and is translatable from an unactuated position to an actuated position, whereby the translation rotates the activation switch from the unactivated position to the activated position thereof.
