The drugs were in a car which was stolen from a veterinary surgery in Upper Poppleton between 4pm on Sunday 3 March and 7.30am on Monday 4 March 2013.
The thieves stole the vehicle’s keys and a small amount of money from the premises before taking the car.
The red Ford Focus bears the registration number YY56OXL.
All of the boxes of drugs are clearly marked that the contents are for the treatment of animals and not for human use. The drugs will cause serious health issues or could even prove fatal if used incorrectly.
Police Sergeant Nicola Peters, of York Safer Neighbourhood Team, said:
I am urging anyone who has any information about the theft of the vehicle and the drugs to contact the police straight away.
The drugs are intended for use on animals and could prove extremely hazardous if they fall into the wrong hands.
If you are the person who stole the car and you still have these drugs in your possession I urge you not to just throw them away or dump them. They need to be disposed of in a safe manner.
If anybody finds the drugs, I ask that they are handed in at a local police station or a veterinary practice straight away.
Anyone who can help to identify the thieves or assist with the safe return of the missing drugs is asked to contact North Yorkshire Police straight away on 101, select option 1 and pass the information to the Force Control Room.
Anyone with information about the burglary or the stolen Ford Focus is asked to contact York CID on 101, select option 2 and ask for Simon Fennell.
Or call Crimestoppers anonymously on 0800 555 111 quoting reference number 12130035486.