Withdrawal time All antibacterial preparations and many other drugs have a withdrawal time. This is the amount of time that must elapse after the last dose of the drug was administered to the animal before it can be slaughtered or any of it's products used for food. Withdrawal times vary considerably depending upon the individual drug and the formulation of the drug that is used. Expiration date All injectable antibiotics and vaccines, many oral products and some other drugs have an expiration date stamped on the label and on the box in which the drug is packed. Antibiotics degrade over time and can form harmful breakdown products.
Vaccines lose their potency.
Some drugs expire more quickly than others. The expiry date is determined by the manufacturer and indicates that the product should be perfectly safe and effective until the expiry date provided it has been stored and handled properly. Storage requirements Some drugs may be stored at room temperature while others require a cooler temperature which is indicated on the label. All drugs should be protected from freezing and excessive heat. Medicated feeds should be stored separately from non-medicated feeds.