Final answer:
The action of Viagra, used to treat erectile dysfunction, persists for up to 4 hours. Sildenafil, the drug's active ingredient, is a PDE5 inhibitor originally tested for heart conditions but later approved by the FDA in 1998 for ED. Patients with cardiac disease on nitrates should consult their doctor before use.
Step-by-step explanation:
A patient diagnosed with erectile dysfunction (ED) and advised to take Viagra should know that the action of the drug persists for up to 4 hours. Sildenafil, the active ingredient in Viagra, is a PDE5 inhibitor that was initially investigated for the treatment of hypertension and angina pectoris. During clinical trials in the 1990s, it was not found to be effective for these heart conditions but was noted to promote erections in many men. In 1998, the Food and Drug Administration (FDA) approved sildenafil for use in treating ED, and it is now widely known to be effective in treating approximately 70 to 85 percent of cases of ED.
It is important for individuals with certain health problems, particularly those with cardiac disease who are taking nitrates, to consult their physician before using Viagra. This is due to the risk of potentially fatal interactions. Therefore, such individuals should either avoid Viagra or undergo thorough medical evaluation to determine if they are suitable candidates for this medication.