Final answer:
A pharmacist cannot substitute a generic drug for a prescribed brand name drug if it is specified by state laws or by 'Dispense as Written' instructions from the prescriber to not substitute.
Step-by-step explanation:
A pharmacist may NOT substitute a generic drug for a prescribed brand name drug if it is listed on the 'Do Not Substitute' or similar lists that are provided by state laws or if the prescriber specifies 'Dispense as Written' (DAW) on the prescription. When a drug is on such a list, it means that there must be no substitution with a generic equivalent. While generic drugs are usually considered therapeutically equivalent to their brand name counterparts, exceptions can be made based on various factors including patient allergies, specific drug formulations, or other clinical reasons. These restrictions help ensure patient safety and preserve the prescriber's intent in cases where a specific medication's properties are crucial for treatment.