Bees are classed in law as food producing animals so as beekeepers we must keep the documentation containing details of any medicinal products administered to them. The records relating to the product used must be kept for at least five years following its administration or other disposal of the product, irrespective of whether or not the colony concerned is in your possession, has been sold on or has died. More details can be found on Beebase
You can find a medicines record card here, also on the Beebase website.