Final answer:
The nurse should instruct the client with pericarditis to take the prescribed NSAID with food. This helps protect the stomach and reduces the risk of gastrointestinal ulcers and bleeds.
Step-by-step explanation:
The nurse should instruct the client with pericarditis to take the prescribed NSAID with food. This is because NSAIDs can irritate the stomach lining and increase the risk of gastrointestinal ulcers and bleeds. Taking the medication with food can help protect the stomach and reduce these risks.