Erectile Dysfunction

Question 1

How does a penile erection occur from initiation to loss of erection?

Answer 1

sexual stimulation activates the parasympathetic nervous system, which releases nitric oxide (NO) in the nerve endings of the penis. NO then activates the enzyme guanylate cyclase which converts guanosine triphosphate into cyclic guanosine monophosphate (cGMP). cGMP then causes a decrease in intracellular calcium levels leading to relaxation of the smooth muscle walls in the cavernosal arteries of the penis. this relaxation of smooth muscles results in dilation of the cavernosal arteries and increased blood flow into the erectile tissues. the expanding erectile tissue compresses the venous plexus reducing venous outflow. This process traps blood within the erectile tissue, resulting in penile rigidity. The erection is maintained as long as cGMP levels remain elevated, keeping the smooth muscle relaxed and blood trapped within the corpora cavernosa. PDE-5 eventually breaks down cGMP causing loss of erection.

Question 2

What are nonpharmacological interventions for treating ED?

Answer 2

1. penile implants which involve placing a prosthesis in the penis to allow for an erection
2. intrapenile injections or intraurethral suppositories of alprostadil which help to induce an erection.

Question 3

what are the most common pharmacological treatments for ED?

Answer 3

1. PDE-5 inhibitors
2. alprostadil (used for those who cannot tolerate oral medications.)

Question 4

what are considerations that should be taken for patients before putting them on PDE-5 inhibitors?

Answer 4

1. caution for those taking nitrates due to risk of severe hypotension
2. severe renal or hepatic disease

Question 5

What is the MOA of PDE-5 inhibitors?

Answer 5

They inhibit the PDE-5 enzyme, which breaks down cyclic GMP (cGMP) in the corpus cavernosum.

Question 6

What is the onset of action of sildenafil (Viagra)?

Answer 6

60 minutes

Question 7

What are risks associated with taking PDE-5 inhibitors?

Answer 7

1. contraindicated with nitrates
2. can potentiate hypotension; caution with other medications that lower BP particularly alpha blockers and nitrates
3. side effects include headaches, dyspepsia, nasal stuffiness, and disturbances in color perception (especially blue-green color vision).
4. Tadalafil can have prolonged side effects due to its longer half-life.

Question 8

What are the benefits of taking Tadalafil?

Answer 8

1. Longer half-life (18 hours) allows for more spontaneous sexual activity.
2. Onset of action is about 120 minutes.
3. FDA approved for benign prostatic hyperplasia (BPH).

Question 9

What is onset of action for Avanafil?

Answer 9

Faster onset of action (30-45 minutes).