How can a medication's effectiveness be assessed?

Assessing a medication's effectiveness primarily relies on monitoring the patient's symptom improvement. This approach involves observing changes in the patient's condition as a direct response to the administered medication. If the symptoms for which the medication was prescribed show significant improvement, it suggests that the medication is effective. This assessment allows healthcare providers to determine not only the efficacy of the drug but also to make necessary adjustments to the treatment plan if the expected improvement is not observed.

The other options provide different types of information that may support the medication management process but do not directly assess effectiveness. For instance, checking the expiration date is critical for ensuring safety and potency but does not evaluate how well the medication works. The physician's order outlines the prescribed treatment but does not measure the outcomes of that treatment. Consulting the manufacturer may provide information on the medication's properties or usage guidelines, but it does not offer real-time data about how the drug is affecting the specific patient. Thus, the most relevant method for assessing a medication's effectiveness is indeed through the monitoring of symptom improvement.