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Lexicon
Sexual function

Alprostadil

Prostaglandin E1 for treating erectile dysfunction, a clinically established but delicate agent with sensitive use.

2 min read 8 sources

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Vial with white powder, a blue cap and a black TPD label for Alprostadil on a white podium, next to it an elongated molecule model of blue and white glass spheres in a bright lab
Compound approved · in the USA since 1981

Summary

At a glance

Sources checked on 26 Oct 2026

Injections followed by sexual activity
94 %

self-injection over six months, 683 men, without placebo1

Intercourse at home (urethra)
64.9 %

at least once in three months, 18.6 percent with placebo2

Penile pain
37 %

most common side effect with injection, 2 percent with placebo5

Priapism
0.4 %

erection over 6 hours, plus 4 percent prolonged erections of 4 to 6 hours5

  • Alprostadil is the drug form of prostaglandin E1. The compound has been approved in the USA since 1981, today also for injection into the erectile tissue in erectile dysfunction.56
  • It relaxes the smooth muscle in the erectile tissue and widens its arteries. To do so it binds to prostaglandin receptors and raises the messenger cAMP inside the cells.56
  • In 683 men 94 percent of self-injections were followed by sexual activity. Given into the urethra, 64.9 percent had intercourse at home versus 18.6 percent with placebo.12
  • The most common side effect is penile pain. The main risks are prolonged erections and rarely priapism, which needs immediate medical treatment.5
  • The prescribing information has the first injections given in the doctor's office. Everything here is information, not a recommendation.5
Profile

Updated May 2026

Class
Prostaglandin E1

vasodilator

Use
Local

medical, 20mcg vials

Purpose
Erectile dysfunction
Status
Clinically established

medical

Sizes
20MCG/5vials

1 size in the shop

Contents 14 sections
  1. At a glance
  2. What is Alprostadil?
  3. How it works
  4. Use
  5. Dosing
  6. What the research shows
  7. Research status
  8. Side effects
  9. Practice
  10. Storage
  11. Related compounds
  12. FAQ
  13. Glossary
  14. Sources

What is Alprostadil?

Alprostadil is the medical form of prostaglandin E1 (PGE1), a vessel-widening messenger. It is a clinically established agent for treating erectile dysfunction and is prescribed for that indication. We carry it as 20mcg vials with freeze-dried powder that is dissolved before use (as in the US prescribing information).

Important: alprostadil is a medical agent with sensitive use. The classic application (intracavernosal injection) is a medically guided procedure, not a casual research experiment.

Comparison

Approaches to erectile dysfunction

Compounds from the TPD lexicon, as described there. Tap a card to open its entry.

Prostaglandin, used locally Alprostadil EP receptors
PDE5 inhibitor as a tablet Sildenafil PDE5 PDE5 inhibitor as a tablet Tadalafil PDE5 Melanocortin agonist PT-141 MC4R

Simplified from the lexicon entries. Alprostadil acts directly in the erectile tissue, the other compounds act at other points. This page shows no direct comparison. 5

How it works

Alprostadil widens the blood vessels and relaxes the smooth muscle. Applied locally it increases circulation and can so trigger an erection, independent of sexual stimulation. That is exactly what makes it an effective agent for erectile dysfunction when tablets (like sildenafil/tadalafil) are not enough.

Where it acts

Where alprostadil acts

Tap a point or a card. Colour = receptor, grey = approved use.

  1. Erectile tissue and arteries

    Relaxes the smooth muscle in the erectile tissue and widens its arteries, blood is trapped5

    EP1EP2
  2. Heart (newborns)

    Keeps a blood vessel at the heart open in newborns (approved use)6

    Observed in trials

Targets in the ChEMBL database6

Compound CHEMBL495: two recorded mechanisms, all Agonist according to ChEMBL.

Prostaglandin E2 receptor EP1
Gene
PTGER1
UniProt
P34995
ChEMBL
CHEMBL1811
Action
Agonist according to ChEMBL
Prostaglandin E2 receptor EP2
Gene
PTGER2
UniProt
P43116
ChEMBL
CHEMBL1881
Action
Agonist according to ChEMBL
Glass vessel ring wrapped in pink muscle bands with two blue molecules resting on them, the open vessel lumen in the centre
Vessels widen when the smooth muscle relaxes. Symbolic image.

Use

Dosing. Loading the dosing information …

Dosing

Dosing

Dosing, titration and syringe

Loading the dosing information …

  • Getting started and stepping up, drawn as a staircase
  • Units on the U-100 syringe for every step
  • How long one vial lasts

What the research shows

A clinical study (Linet, NEJM 1996) showed that intracavernosal alprostadil was effective in men with erectile dysfunction with tolerable side effects and a clear dose-response relationship. So alprostadil is a well-evidenced, medically established agent, the sensitive application is the decisive point.

Study results

What the trials measured

Interactive: switch tabs, tap points, show or hide arms. Arms are named relative to each other, no dosing advice.

Successful intercourse at home2

Share of men with intercourse at least once in three months

Given into the urethra2 461 with alprostadil, 500 with placebo
Placebo 18.6%
Alprostadil 64.9%

Values from the abstract. Only men who responded in the clinic continued at home (65.9 percent of 1,511). Given as a small pellet into the urethra, not as an injection. No priapism and no fibrosis in this study.

Self-injection into the erectile tissue1

Share of injections, 683 men over six months

Sexual activity possible1
Alprostadil 94%
Satisfied (men)1
Alprostadil 87%
Satisfied (partners)1
Alprostadil 86%

Values from the abstract, open study without placebo. In a second part with 296 men all doses were better than placebo, with a clear dose-response relationship.

Circulatory disorder of the legs, stage IV4

Share of participants in percent, 840 participants, infusion

Complete wound healing4 12 weeks after treatment
Placebo 17.2%
Alprostadil 18.4%
Major amputation4 24 weeks after treatment
Placebo 14.6%
Alprostadil 12.6%

Values from the abstract. In this other use alprostadil was not superior to placebo, the differences were not significant.

Petri dish with a reddish piece of blood vessel and a red rose petal on the stage of a microscope
Studied in a clinical trial with a clear dose-response relationship, use belongs in medical hands. Symbolic image.

Research status

Where the research stands

Alprostadil has been approved since 1981, the approval studies in erectile dysfunction ran before the registry existed. A search for alprostadil and erectile dysfunction finds 14 entries there, many use the compound only as a tool. Shown are trials with alprostadil as the tested agent, plus a large trial on circulation in the legs. As of 26 Oct 2026. 7

  1. Preclinical Prostaglandin E1, a messenger made by the body
  2. Phase 1 1 trial, 1 completed
  3. Phase 2 3 trials, 1 completed, 1 stopped early
  4. Phase 3 2 trials, 1 completed, 1 stopped early
  5. Approval in the USA since 1981
48 participants in phase 3 Approved in the USA since 1981. Uses according to ChEMBL include erectile dysfunction and keeping a blood vessel at the heart open in newborns (ductus arteriosus).5
Show all 6 phase 2, 3 and 4 trials on a timelineHide timeline 3 completed 1 running 2 stopped early 1 with results
Phase 2
Phase 3
Phase 4

Bar: start to primary endpoint (planned for running trials). Green = completed, blue = progress until 26 Oct 2026, grey = stopped early. Phase 1: 1 trial on safety and pharmacokinetics, not shown as bars.

Side effects

  • Painful prolonged erection (priapism), an emergency that must be treated medically.
  • Pain or burning at the application site.
  • Dizziness, drop in blood pressure.

Tolerability

Local side effects with injection

Out of 100 men per group, how many had the event in studies of up to 18 months (1,861 with alprostadil, 294 with placebo).

2 of 100 Placebo
37 of 100 Alprostadil
Event PlaceboAlprostadil
Penile pain5 2%37%
Prolonged erection (4 to 6 hours)5 0%4%
Hardening in the penis (fibrosis)5 0%3%
Bruise at the injection site5 0%3%
Dizziness5 0%1%

Values from the US prescribing information. With placebo no local or general side effect occurred apart from penile pain. Priapism over 6 hours occurred in 0.4 percent, 3 percent stopped because of pain.5

Practice

  1. A delicate, medically applied agent, not a casual self-experiment.

  2. With an erection lasting more than a few hours, seek medical help immediately (priapism).

  3. For erection problems oral agents (sildenafil/tadalafil) are the first, simpler choice.

Light bedside table with a lamp, a glass of water, a small potted plant, a folded light blue towel and a closed booklet

Storage

According to the US prescribing information, unopened 20mcg vials are stored at room temperature, meaning 20 to 25 °C. Use the dissolved solution within 24 hours, keep it at or below 25 °C, do not put it in the fridge and do not freeze it. Store out of reach of children, keep the original packaging closed and mind the expiry date.

Related

Related compounds

A different path: all in the TPD lexicon.

Alprostadil
Sildenafil Different route: PDE5 inhibitor as a tablet Tadalafil Different route: long-acting PDE5 inhibitor Avanafil (Stendra, Spedra) Different route: PDE5 inhibitor Vardenafil (Levitra) Different route: PDE5 inhibitor Sildenafil + Tadalafil (combo) Combination of two PDE5 inhibitors PT-141 Different route: melanocortin peptide

FAQ

Common questions about Alprostadil

Short answers, each backed by the sources below.

Is alprostadil approved?

Yes. The compound has been approved in the USA since 1981. As an injection into the erectile tissue it is approved for erectile dysfunction and as an aid in diagnosis. Another approved use is in newborns to keep a blood vessel at the heart open.56

How does alprostadil work?

Alprostadil binds to prostaglandin receptors in the erectile tissue and raises the messenger cAMP inside the cells. The smooth muscle relaxes and the arteries widen. Blood flows in and is held in the erectile tissue.56

What do the studies show?

In a study of 683 men who injected themselves for six months, 94 percent of injections were followed by sexual activity. Men and partners were satisfied after 87 and 86 percent. Given into the urethra, 64.9 percent of men had intercourse at home versus 18.6 percent with placebo.12

Which side effects are known?

Most common is penile pain: 37 percent in the approval studies versus 2 percent with placebo, mostly mild to moderate. There were also prolonged erections (4 percent), hardening (3 percent) and bruising (3 percent). Given into the urethra, blood pressure dropped in 3.3 percent in the clinic.52

What is priapism?

An erection that lasts longer than 6 hours. In the studies it occurred in 0.4 percent. The prescribing information says: if an erection lasts longer than 4 hours, get medical help immediately. Untreated, the tissue can be damaged permanently.5

Who should not use alprostadil?

According to the prescribing information not with a tendency to priapism (such as sickle cell disease, multiple myeloma or leukaemia), with hardening or curvature of the penis, with a penile implant or with hypersensitivity to the compound.5

Do spontaneous erections come back?

In an open study of men with circulation-related erectile dysfunction, 85 percent of 54 men with data reported during a year of self-injection that spontaneous erections had become more frequent. Blood flow in the erectile arteries had increased. There was no comparison group.3

Glossary

Terms explained briefly

Dotted words in the text open these explanations directly.

cAMP
A messenger inside the cell. When it rises in smooth muscle, the muscle relaxes.
Ductus arteriosus
A blood vessel between the pulmonary artery and the aorta that normally closes after birth.
Erectile tissue
Spongy tissue in the penis that fills with blood during an erection.
Fibrosis
Hardening caused by extra connective tissue. In the penis it can lead to curvature.
Intracavernosal
Into the erectile tissue. This is how alprostadil is injected.
PDE5 inhibitor
Tablet compounds such as sildenafil or tadalafil. They act at a different point of the erection than alprostadil.
Priapism
An erection lasting longer than 6 hours. An emergency that needs immediate medical treatment.
Prostaglandin E1
A messenger made by the body, from the prostaglandin family. Alprostadil is its drug form.
Smooth muscle
Muscle that is not under voluntary control, for example in vessels and in the erectile tissue.

Evidence

Sources

Show all 8 sourcesHide sources 4 Studies1 Trial registry3 Database checked 26 Oct 2026

Studies

  1. Efficacy and safety of injection into the erectile tissue, three studies

    Linet und Ogrinc, New England Journal of Medicine, 1996

    DOI 10.1056/NEJM199604043341401 PMID 8596569
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed
  2. Alprostadil into the urethra versus placebo, 1,511 men

    Padma-Nathan et al., New England Journal of Medicine, 1997

    DOI 10.1056/NEJM199701023360101 PMID 8970933
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed
  3. Spontaneous erections during long-term self-injection

    Brock et al., Urology, 2001

    DOI 10.1016/s0090-4295(00)01027-x PMID 11248634
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed
  4. ESPECIAL: alprostadil in leg circulation disorder, phase 4

    Lawall et al., European Journal of Vascular and Endovascular Surgery, 2017

    DOI 10.1016/j.ejvs.2016.12.035 PMID 28189475 NCT00596752
    Checked 26 Oct 2026 via doi.org, Crossref, PubMed

Trial registry

  1. Trials with alprostadil in erectile dysfunction in the registry

    ClinicalTrials.gov, U.S. National Library of Medicine

    Checked 26 Oct 2026 via ClinicalTrials.gov API v2

Database

  1. US prescribing information for injection into the erectile tissue

    DailyMed, U.S. National Library of Medicine (Fachinformation, Stand 2024)

    Checked 26 Oct 2026 via DailyMed
  2. Alprostadil in ChEMBL (mechanism, approval, uses)

    ChEMBL, EMBL-EBI (CHEMBL495)

    Checked 26 Oct 2026 via ChEMBL
  3. Structure of alprostadil in PubChem

    PubChem, U.S. National Library of Medicine (CID 5280723)

    Checked 26 Oct 2026 via PubChem

In the shop

Alprostadil in the catalog

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