Final answer:
Federal law, specifically through the FDA, does not put a strict limit on prescription validity, as this is typically governed by state laws. The exact duration can vary, with controlled substances having stricter controls. Medicare legislation aims at assisting with prescription drug costs but does not set prescription validity periods.
Step-by-step explanation:
The question of whether federal law puts a limit on how long a prescription is valid does not have a simple yes or no answer because it can vary depending on the type of prescription and state laws. However generally speaking, for most medications federal regulations set by the Food and Drug Administration (FDA) do not specifically outline an expiration for the validity of a prescription.
Prescription validity is often determined by state laws and can also depend on the type of medication prescribed – for example controlled substances usually have stricter limits. In contrast, Medicare-related legislation, such as the Medicare Prescription Drug and Modernization Act of 2003, focuses on providing prescription drug benefits to the elderly rather than setting prescription validity periods.