INTRACAVERNOSA ALPROSTADIL - GENERAL INFORMATION

Question 1

What are three characteristics of intracavernosal alprostadil?

Answer 1

Dose-Effect Relationship: Alprostadil’s effectiveness is linked to the dose. Higher doses lead to longer erections, typically ranging from 12 to 44 minutes.
Response in Erectile Dysfunction Types: Patients with psychogenic and neurogenic erectile dysfunction often respond to lower alprostadil doses compared to those with vasculogenic erectile dysfunction.
Tolerance Development: Tolerance does not seem to develop with continuous use of intracavernosal alprostadil at home.

Question 2

How can patients who do not respond to usual doses of intracavernosal alprostadil be treated?

Answer 2

Combination with VEDs: Intracavernosal alprostadil can be used successfully alongside Vacuum Erectile Devices (VEDs) for patients who don’t respond to regular doses. This combination therapy can be attempted before considering more invasive surgical options.
Synergistic Drug Combinations: Intracavernosal injections of synergistic combinations of vasoactive agents with different mechanisms of action, such as papaverine and phentolamine, have been used. These combinations often result in a longer-lasting erection compared to using a single agent. Additionally, they tend to have fewer adverse effects due to the lower dosage of each agent in the mix.
Combination with Phosphodiesterase Type 5 Inhibitors: Intracavernosal alprostadil can be used in combination with phosphodiesterase type 5 inhibitors, although this use is considered an unlabeled indication.

Question 3

How fast does alprostadil act when administered intracavernosally?

Answer 3

Alprostadil acts rapidly, typically with an onset of 5 to 15 minutes.

Question 4

What is the typical duration of an erection with intracavernosal alprostadil within the usual dosage range?

Answer 4

Within the usual dosage range of 2.5 to 20 mcg, the duration of an erection is usually not more than 1 hour.

Question 5

How is alprostadil metabolized in the corpora cavernosum?

Answer 5

Local 15-hydroxy dehydrogenase in the corpora cavernosum quickly converts alprostadil to inactive metabolites.

Question 6

How is alprostadil eliminated from the systemic circulation?

Answer 6

Any alprostadil that escapes into the systemic circulation is deactivated on first pass through the lungs.

Question 7

What is the plasma half-life of alprostadil?

Answer 7

The plasma half-life of alprostadil is approximately 5 to 10 minutes.

Question 8

What are examples of vasoactive agents used in intracavernosal drug combinations?

Answer 8

Papaverine (a nonspecific phosphodiesterase inhibitor) and phentolamine (an alpha-adrenergic antagonist) are used in intracavernosal drug combinations.

Question 9

What is a potential treatment approach for patients not responding to usual doses of intracavernosal alprostadil?

Answer 9

Combination therapy with intracavernosal alprostadil and vacuum erectile devices (VEDs) has been used successfully in these cases.

Question 10

What is the usual dose range of intracavernosal alprostadil?

Answer 10

The usual dose of intracavernosal alprostadil is 10 to 20 mcg, with a maximum recommended dose of 60 mcg.

Question 11

What can doses greater than 60 mcg of intracavernosal alprostadil cause?

Answer 11

Doses greater than 60 mcg have not shown greater improvement in penile erection but may cause hypotension or prolonged erections lasting more than 1 hour.

Question 12

When should the dose of intracavernosal alprostadil be administered?

Answer 12

The dose of intracavernosal alprostadil should be administered 5 to 10 minutes before intercourse.

Question 13

What is the recommended approach for titrating the dose of intracavernosal alprostadil?

Answer 13

Patients should be started with a 1.25 mcg dose, which can be increased in increments of 1.25 to 2.50 mcg at 30-minute intervals up to the lowest effective dose.

Question 14

What is the maximum frequency of intracavernosal alprostadil injections to avoid adverse effects?

Answer 14

Patients should receive not more than one injection per day and not more than three injections per week with a 24-hour interval between doses.

Question 15

What gauge needle is typically used for intracavernosal injections of alprostadil?

Answer 15

A 27 or 30-gauge needle is commonly used for intracavernosal injections of alprostadil.

Question 16

How should the penis be positioned during intracavernosal injection to avoid complications?

Answer 16

The injection should be made at right angles into one of the lateral surfaces of the proximal third of the penis. The injection should never be made into the dorsal or ventral surface to prevent inadvertent injection of the drug into arteries on the dorsal surface or the urethra on the ventral surface.

Question 17

What should be done after the injection of intracavernosal alprostadil?

Answer 17

After the injection, the penis should be massaged to help distribute the drug into the opposite corpus cavernosum. Injection sites should be rotated with each dose.

Question 18

What is recommended to reduce the likelihood of hematoma formation after an intracavernosal injection?

Answer 18

Manual pressure should be applied to the injection site for 5 minutes to reduce the likelihood of hematoma formation.