Final answer:
The medical assistant should ask the patient to come in for a follow-up appointment when a medication is not working.
Step-by-step explanation:
When a patient calls into the office to report that a medication is not working, the medical assistant should ask the patient to come in for a follow-up appointment (Option 3). This allows the healthcare provider to assess the effectiveness of the medication and determine if any adjustments need to be made. Directly telling the patient to stop taking the medication (Option 1) or recommending an immediate visit to the emergency room (Option 2) without further information could be inappropriate and potentially harmful. Instructing the patient to continue the medication as prescribed (Option 4) may also not be the best course of action if the medication is truly not working.