An actuation inhibitor for metered dose inhalers comprises an annular band of semi-rigid plastics material having a substantially circular cross-section, with an upstanding wall encompassing from about 260 to 315, a gap in the wall of from about 45 to 100, and a pair of outwardly projecting walls, one at each side of the gap. The inside diameter when at rest in an unstressed manner is slightly smaller than that of a medication canister. The height is from about 40% to 65% of the predetermined diameter, and the length of each of the projecting walls is from about 10% to 50% of the height. The semi-rigid plastics material is sufficiently flexible to permit the pair of projecting walls to be spaced apart one from the other by up to about a further 90, and the plastic memory permits the spreading apart of the projecting walls without being overcome.