A Client Is to Receive Sildenafil Citrate (Viagra) for Erectile

A client is to receive sildenafil citrate (Viagra) for erectile dysfunction. In teaching the client, the nurse discovers that the client is taking nitroglycerin (NTG) prn angina. Which instruction is a priority at this time?

A) Tell the client to take both medications as ordered by the healthcare provider.
B) Tell the client not to take the NTG until 1 hour after a dose of Viagra if angina occurs.
C) Ask the client to watch for signs of postural hypotension, including dizziness.
D) Refer the client to the healthcare provider because taking both medications is contraindicated.