Opioid ketal compounds and uses thereof

A pharmaceutical composition, comprising a compound of Formula I:

• or a pharmaceutically acceptable salt thereof, wherein
• R1 is H or CH3,
• R2 is H,
• n is 0, 1, 2 or 3,
• R3 and R4 are independently H or optionally substituted C1-C4 alkyl, or
• when n is 0, then R3 and R4 and the carbon atoms to which they are attached together form a six or seven membered ring, which is optionally mono or disubstituted by C1-C4 alkyl, and wherein when R3 or R4 is other than hydrogen, the carbon atoms labeled * and ** are independently in the R or S configuration;
• with the proviso that the compound is not hydrocodone ethyleneglycol ketal or hydromorphone ethyleneglycol ketal,
• or a mixture of compounds of Formula I or the pharmaceutically acceptable salts thereof, and a pharmaceutically acceptable carrier.