Although Vasodilating Drugs Such as Papaverine and Prostaglandin Are Effective

Although vasodilating drugs such as papaverine and prostaglandin are effective in producing an erection for patients with erectile dysfunction, many patients discontinue use of the drugs because of

A) pain associated with drug administration.
B) the fact that these drugs eventually cure the disorder.
C) the expense of the drug.
D) the fact that the effectiveness of the drug decreases with continued use.