Which statement best describes the Avilamycin example regarding expiration vs duration?

• A. Expiration date is 180 days; duration is 90 days
• B. Expiration date is 21 days; duration of use is 90 days
• C. Expiration date is 90 days; duration of use is 21 days
• D. Expiration date and duration of use are always equal

Answer: (C)

The key idea is that expiration date and duration of use are two different things on a veterinary drug label. The expiration date tells you how long the product is guaranteed to retain potency and safety if stored properly; it’s about shelf life. The duration of use tells you how long you are permitted to administer the product to animals in a single course or feeding cycle; it’s about how long the treatment can actively continue, regardless of how long the product might still be good on the shelf.

In the Avilamycin example, the product has an expiration date of 90 days, meaning you should use or discard it within 90 days of manufacture to ensure effectiveness. The duration of use is 21 days, meaning you can feed it to the animals for up to 21 days in a single treatment period. After that, you would stop the product and follow any withdrawal requirements.

Other options mix these timelines in ways that don’t align with labeling practices (e.g., longer shelf life paired with a long continuous use, or equal expiration and use durations). This example makes clear that shelf life and permitted usage duration are not the same and should be treated separately.