Final answer:
Mr. Martin should report the symptom of a tarry stool to his healthcare provider immediately, as this could indicate serious gastrointestinal bleeding, a side effect of NSAIDs like ibuprofen.
Step-by-step explanation:
Mr. Martin, age 64, who has been prescribed ibuprofen for osteoarthritis, should be particularly vigilant for the symptom of a tarry stool. This can be indicative of gastrointestinal bleeding, which is a serious potential side effect of non-steroidal anti-inflammatory drugs (NSAIDs) like ibuprofen. Older patients, such as Mr. Martin, are especially at risk of gastrointestinal issues, and NSAIDs can exacerbate this risk. Therefore, if Mr. Martin notices tarry stools, he should report this to his healthcare provider immediately as it may suggest a gastrointestinal bleed, which requires urgent medical attention.