Final answer:
The Pain scale should be used to assess the therapeutic effects of the medication acetaminophen-aspirin-caffeine on a client with a migraine.
Step-by-step explanation:
The method that should be used to assess for the therapeutic effects of the medication acetaminophen-aspirin-caffeine is the Pain scale.
When a client is diagnosed with a migraine and is given a medication for relief, the effectiveness of the medication can be determined by assessing the level of pain experienced by the client. Using a pain scale, such as the Wong-Baker Faces pain-rating scale, patients can rate their pain on a scale of 0-10. This allows healthcare providers to evaluate the effectiveness of the medication in reducing the client's pain.