Alprostadil
Alprostadil is the prostaglandin E1 used for erectile dysfunction when oral PDE5 inhibitors are ineffective or contraindicated. It is administered as intracavernosal injection (Caverject, Edex) or as a urethral pellet (Muse), producing reliable erection within minutes through direct vasodilation.
- Chemical formula
- C20H34O5
- CAS number
- 745-65-3
- ATC code
- G04BE01
- Molecular weight
- 354.49 g/mol
- Drug class
- Prostaglandin E1 (PGE1)
- Also known as
- Caverject, Edex, Muse, PGE1, Prostaglandin E1
What is it?
Alprostadil is synthetic prostaglandin E1 (PGE1), in clinical use since the 1980s and FDA-approved for erectile dysfunction in 1995 (intracavernosal Caverject, Edex) and 1996 (intraurethral Muse). It is on the WHO Essential Medicines List. Authorised generic alprostadil is available across all formulations. It is the most widely used non-PDE5-inhibitor pharmacological treatment for erectile dysfunction, valued for predictable response and effectiveness in patients who do not respond to oral therapy (post-prostatectomy, severe vascular disease, severe diabetes).
Mechanism of action
Alprostadil binds prostaglandin E receptors on smooth muscle of the corpus cavernosum, triggering cAMP-mediated relaxation of cavernosal smooth muscle independent of the nitric oxide pathway used by PDE5 inhibitors. This produces direct vasodilation in the corpora cavernosa with reliable engorgement within 5–20 minutes of administration. Because the mechanism does not require sexual stimulation or intact NO pathways, alprostadil works in many patients who do not respond to oral PDE5 inhibitors.
Pharmacokinetics
Alprostadil has a very short systemic half-life (minutes) due to rapid pulmonary first-pass metabolism. Local administration into the cavernosum or urethra delivers the drug directly to its site of action with limited systemic exposure. Onset of erection is 5–20 minutes after intracavernosal injection and 5–10 minutes after urethral pellet, with duration 30–60 minutes.
Indications
Alprostadil is approved for erectile dysfunction of vasculogenic, neurogenic, psychogenic or mixed aetiology in adult men. It is widely used after prostatectomy for penile rehabilitation, in patients who fail or cannot use PDE5 inhibitors, and in those with cardiovascular contraindications to oral therapy. According to current ED guidelines, alprostadil is second-line after oral PDE5 inhibitors but first-line in selected populations.
Safety profile
Common adverse effects include penile pain (most common with intracavernosal injection), hypotension, dizziness, urethral burning (with Muse), priapism (rare but serious), penile fibrosis with prolonged use, and small risk of urinary tract bleeding. Strict adherence to dosing, training in injection or insertion technique, and immediate medical attention for erections lasting over 4 hours are essential. Combination with oral PDE5 inhibitors is generally avoided due to risk of severe hypotension and priapism.
Products containing this ingredient
Frequently asked questions
When is alprostadil used instead of pills like Viagra or Cialis? ▾
Alprostadil is used when oral PDE5 inhibitors are ineffective (some patients with diabetes, severe vascular disease, or after prostatectomy), contraindicated (concurrent nitrates, severe cardiovascular disease) or insufficient. According to current ED guidelines, oral PDE5 inhibitors are first-line for most men, with alprostadil reserved for non-responders or those with contraindications.
What is the difference between Caverject and Muse? ▾
Caverject (and Edex) is an intracavernosal injection given through a fine needle into the side of the penis, with onset in 5–20 minutes. Muse is a small pellet inserted into the urethra, with onset in 5–10 minutes. Injection is more effective and reliable but requires comfort with the injection technique; the urethral pellet avoids needles but is less reliable and often less effective.
What should I do if an erection lasts too long after alprostadil? ▾
Erections lasting more than 4 hours (priapism) require urgent medical attention because prolonged engorgement can damage cavernosal tissue. According to the prescribing information, patients are counselled in advance to seek emergency care if an erection exceeds 4 hours. Priapism is rare with correctly dosed alprostadil but is the most serious adverse event.
The information on this website is provided for reference and educational purposes only. It does not replace consultation with a qualified healthcare professional.