Alprostadil is the synthetic form of prostaglandin E1 (PGE1), a potent vasodilator. It is FDA-approved in multiple formulations: Caverject and Edex (intracavernosal injection for erectile dysfunction), Muse (urethral suppository for ED), and IV Alprostadil/Prostin VR Pediatric (for maintaining patent ductus arteriosus in neonates with congenital heart disease awaiting surgery). Alprostadil-cream formulations (Vitaros) are also approved in some jurisdictions for ED.
Quick Start
Route
Intracavernosal (Caverject/Edex), urethral (Muse), topical cream (Vitaros), or IV (neonatal)
Start low
1.25-2.5mcg IV
Frequency
Pre-intercourse (ED) or continuous infusion (neonatal)
Pre-intercourse for ED. Specific clinical setting for neonatal use. Per FDA label for each formulation.
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Start here. Every protocol below is ordered lowest-first. Begin at the smallest effective dose, hold about a week to assess tolerance, and step up only if needed.
Tiered Protocols · lowest first
Conservative start
1.25-2.5mcg intracavernosal (initial trial dose) · Intracavernosal (Caverject/Edex), urethral (Muse), topical cream (Vitaros), or IV (neonatal) · Pre-intercourse (ED) or continuous infusion (neonatal)
conservative starter
1.25-2.5mcg intracavernosal (initial trial dose)
Pre-intercourse (ED) or continuous infusion (neonatal)
Expert
Intracavernosal Injection
5-20 mcg · IM · As needed
human clinical trial · Linet et al. 1996 (N Engl J Med)
Route is strictly intracavernosal (injected directly into the base of the penis). Listed as IM for database limitations.
5-20 mcg
As needed
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How it works
Alprostadil is synthetic prostaglandin E1, a potent endogenous vasodilator and platelet aggregation inhibitor:
EP Receptor Activation
PGE1 binds EP1, EP2, EP3, and EP4 receptors on vascular smooth muscle and other tissues. EP2/EP4 activation increases cAMP, producing smooth muscle relaxation and vasodilation. EP1/EP3 have more complex effects on platelets and inflammatory responses.
Corporal Smooth Muscle Relaxation
In the penis, intracavernosal alprostadil produces direct corporal smooth muscle relaxation via cAMP elevation, allowing arterial inflow and venous outflow restriction - producing an erection independent of neural/psychological arousal pathways. This makes it effective even in vascular and neurogenic ED.
Onset and Duration
Erection within 5-15 minutes of intracavernosal injection; lasts 30-90 minutes. Predictable kinetics with proper dose titration.
Pulmonary First-Pass
PGE1 is rapidly cleared by pulmonary endothelial enzymatic degradation (15-deoxy-PGE1 metabolite formation). Plasma half-life ~30-60 seconds. This makes systemic IV use possible only in specific contexts (neonatal ductus arteriosus) where continuous infusion compensates for rapid clearance.
Priapism Risk
Excessive dose or post-treatment intracavernosal alprostadil retention can produce prolonged erection (>4 hours = priapism, urological emergency). Requires careful dose titration and patient education.
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What to expect
Early
Days 1–7
Acute erection within 5-15 minutes of intracavernosal dose.
Mid
Weeks 2–4
Erection 30-90 minutes per dose.
Later
Weeks 4–12
Repeated use generally well-tolerated; long-term fibrotic plaque risk in some patients.
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Evidence
HumanStrong
AnimalStrong
In-vitroPresent
Each reference below was re-fetched from its PubMed record, and the quoted sentence was
confirmed to appear in that abstract and to support the claim it sits under. Follow any of
them to read the source.
Mechanism/route: alprostadil is a synthetic vasodilator identical to prostaglandin E1 and is used intraurethrally or intracavernosally.
When PDE5 inhibitors are not suitable, available options include intraurethral and intracavernosal alprostadil - a synthetic vasodilator chemically identical to the naturally occurring prostaglandin E(1) indicated for the treatment of ED.
Evidence scope. Human; literature review; intraurethral and intracavernosal routes specifically (this paper does not address topical alprostadil).
Route boundary: intracavernosal and intraurethral alprostadil are approved treatment routes in all countries per this source; topical alprostadil, while showing positive Phase III results, had gained regulatory approval only in Canada at the time of this review — not a universally approved route on equal footing with the other two.
Both intracavernosal and intraurethral alprostadil are approved for use in all countries, and following positive results from recent Phase III trials, topical alprostadil has gained approval in Canada.
Evidence scope. Human; narrative review (2013/2014); intracavernosal/intraurethral widely approved, topical approved in Canada only per this source.
Dose/route: intracavernosal alprostadil showed a dose-response from 2.5 to 20 mcg, supporting the card’s 2.5 mcg initial-dose boundary.
In a dose-response study of 296 men, all doses of alprostadil were superior to placebo and there was a significant dose-response relation (P < / = 0.001), resulting in higher response rates with increasing doses of alprostadil (from 2.5 to 20 microg).
No abstract we checked supports these for this molecule at this route. That is not the
same as saying they are false — it marks where the evidence is missing.
Exact 1.25 mcg intracavernosal starting dose. The checked dose-response abstract starts at 2.5 mcg; it does not verify 1.25 mcg.
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Side effects & safety
Commonly reported
Penile pain (burning sensation, common)
Injection site bruising / hematoma
Mild penile fibrosis with repeated use
Prolonged erection (1-4 hours, manageable)
Less common & notes
Priapism (>4 hours, urological emergency requiring aspiration or surgical intervention).
Penile fibrosis or Peyronie-like plaques with chronic use.
Vasovagal syncope post-injection (rare).
Hypotension (rare with intracavernosal due to local action).
Allergic reactions rare.
Neonatal IV use has well-characterized respiratory depression risk - clinical setting only.
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Pharmacokinetics
Illustrative plasma concentration · 0.5 h
Half-life
~30-60 seconds
Plasma (very short - pulmonary first-pass)
Peak · Tmax
5-15 min
Intracavernosal
Elimination
30-90 min
Erection per dose
Bioavailability
Intracavernosal direct local effect
Duration of action
30-90 min
Per intracavernosal dose
Clearance
Pulmonary first-pass enzymatic degradation
Storage. Caverject pen: refrigerate per label. Reconstituted use within 24 hours. Vitaros cream: refrigerate per label.
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Regulatory status
FDA-approved across multiple formulations. Prescription-only. Urology-prescribed for ED indication. Pediatric cardiology-prescribed for ductus arteriosus patency. Generic alprostadil also available.
Put it to work
Calculate, log & track
Open Alprostadil straight into OnePin with your vial and dose pre-filled, then let it handle the syringe math and remind you before the vial runs out.