Merseyside police were called to reports four men had broken into the store in Marine Parade at around 8.50pm yesterday (February 22).
The raiders took money and a safe containing the drugs from the Vets4Pets surgery before escaping in a black Ford Fiesta.
The safe was later found burnt out on the car park of Dobbies Garden Centre in Bentham's Way.
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Det Chief Insp Gayle Rooney said: "I would appeal to anyone who was in the area of Marine Parade at 9pm on Monday who saw or heard anything suspicious to contact us.
"I would also ask anyone who was driving in the area to check their dash-cam in case they captured anything significant."
Anyone with information has been urged to contact Merseyside Police by messaging @MerPolCC or calling 101.
Alternatively, independent charity Crimestoppers can be contacted anonymously on 0800 555 111 or via their website crimestoppers-uk.org.
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