Abstract: A locking cap apparatus includes a cap assembly having an outer cap and an inner cap received within the outer cap, and further includes lock setting members. The outer cap includes an actuator coupled with a plunger. The plunger and the actuator are movable within and relative to the outer and inner cap. The cap assembly is rotatably and releasably coupled with external threads of a bottle. The plunger has a locked position, an unlocked position, and a lock change position, where the outer cap is rotatable relative to the bottle when the plunger is in the locked position, unlocked position, and optionally in the combination change position. Lock setting members are interactively coupled with the shaft of the plunger.