L2 | ED | Alprostadil

Question 1

What is alprostadil? And how does it work?

Answer 1

It is a synthetic PGE-1.
It causes smooth muscle relaxation in the erectile tissue of the penis by an unknown mechanisms, some suggest that it may increases the level of cAMP which activates protein kinase which leads to calcium leaving the cell thereby inducing muscle relaxation which allows for blood to accumulate within the penile tissue thereby causing an erection.

Question 2

What are the preparations found for this drug?

Answer 2

This drug can be found in two main preparations:
1. Urethral suppositories
2. Penile injections

This medication is used for patients who are not candidates for PDE-5 inhibitors.

Question 3

What are its pharmacokinetics?

Answer 3

1. Systemic absorption of this medication is minimal, and if it were to be absorbed, it’ll be immediately metabolized.
2. The onset of action is 5-10 minutes for the suppositories and 2-25 mins for the injection and the effect lasts for 30-60 minutes or longer.

Question 4

How is the injection form administered?

Answer 4

It is either injected in the head of the penis, or the base of the penis near the scrotum dorsolaterally.

Question 5

What are its adverse effects?

Answer 5

Systemic Adverse Effects:
Systemic effects are rare since it’s not well absorbed systemically, however, hypotension or headaches can occur due to the vasodilatory effect of PGE-1

Local Adverse Effects:
1. Penile, urethral or testicular pain
2. Hematoma, ecchymosis and rash are possible by the injectable form
3. Bleeding from the injection site is rare.
4. Although rare, it can lead to priapism.

Question 6

What are some drugs that could cause impotence?

Answer 6

1. Alcohol
2. Anti-hypertensive drugs (atenolol)
3. H2-blockers like cimetidine
4. Lithium
5. Some antidepressants like buspirone, amoxapine
6. Amphetamine
7. Corticosteroids
8. Haloperidol
9. Opiates such as codeine, methadone