Which of the following best describes when a prescription becomes invalid?

A prescription becomes invalid after the expiration date has passed because this date indicates the time frame within which the medication is intended to be safe and effective to use. Once the expiration date is reached, the manufacturer no longer guarantees the potency or safety of the medication, and it should not be dispensed or consumed.

While other circumstances, such as a patient moving to a different state or altering the prescribed dosage, can affect the validity of a prescription in terms of its use or need for new prescriptions, they do not inherently render it invalid. For example, a patient may need a new prescription if they relocate, but the original prescription remains in effect until the expiration date is reached. Similarly, changes in dosage might require adjustments, but the initial prescription remains valid until it technically expires. Administering the medication does not impact its validity; it is about whether the prescription can still be lawfully dispensed or filled. Therefore, the expiration date serves as a definitive point at which a prescription can no longer be considered valid for use.