A client arrives to the emergency department with chest pain after taking sildenafil. Based on the client's history, which medication should the nurse withhold?

A. Morphine can be administered for chest pain to reduce discomfort and anxiety, and it does not have a direct dangerous interaction with sildenafil. B. Aspirin is commonly used in chest pain management to prevent platelet aggregation and does not interact dangerously with sildenafil. C. Heparin is an anticoagulant used in acute coronary syndrome; it is safe to administer with sildenafil and does not pose an immediate interaction risk. D. Nitroglycerin and other nitrates can cause severe hypotension when combined with sildenafil. Withholding nitrates is essential to prevent life-threatening drops in blood pressure in this client.