A 66-year-old man has made an appointment with his primary care provider to discuss his recent ...

A 66-year-old man has made an appointment with his primary care provider to discuss his recent erectile dysfunction (ED) and has requested a prescription for tadalafil (Cialis) based on television commercials he has seen.
 
  What characteristic of this patient would most likely contraindicate the use of tadalafil for his ED?
  A) The patient takes allopurinol for the treatment of gout
  B) The patient has a family history of osteoporosis and has undergone bone density testing
  C) The patient has unstable angina and uses a nitroglycerin patch
  D) The patient often takes ginseng when he gets a common cold