Medicinal compositions for carbon dioxide based metered dose inhalers

A pressurized medicinal composition comprising at least 40%, by weight, of liquid carbon dioxide, a fluid that forms a homogeneous solution with liquid carbon dioxide, and at least one active pharmaceutical ingredient dissolved or suspended in the composition. The composition may have a liquid to supercritical transition temperature greater than 40ºC. Also, metered dose inhalers comprising an actuator, and a canister equipped with a metering valve, wherein the canister houses a reservoir comprising a pressurized carrier fluid mixture for dissolving or suspending at least one active pharmaceutical ingredient, the carrier fluid mixture comprising liquid carbon dioxide and a second component that is a liquid at room temperature and pressure.