Peptides
Alprostadil (PGE1)
Also called Prostaglandin E1 · Caverject · PGE1
Alprostadil is an erection treatment that acts locally to increase blood flow. It can be useful when a clinician chooses injection therapy, but finding the right dose and learning the technique matter: pain and prolonged erections are important trade-offs.
Dosage & duration
US CAVERJECT label; clinician-selected intracavernosal treatment.
Initial office titration
Product label- Dose
- 2.5 mcg initially for most ED types; 1.25 mcg for pure neurogenic ED
- How often
- Home use: no more than 3 times/week, at least 24 hours apart
- How long
- As needed with follow-up
Initial amounts are not universal maintenance doses. Training and individual titration are required.
Sources: 1
How it fits together
Finding an effective erection treatment
CAVERJECT treatment is adjusted to the person's response, starting in the clinic.
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Assess the erection problem
A clinician checks the cause and whether local injection treatment is suitable.
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Establish the dose and technique
Initial injections and dose adjustment take place in the office, with training before home use.
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Review the response
Follow-up checks erection duration, pain and any scarring or new curvature.
What people want from it
The goal is an erection firm enough for intercourse, not a boost in desire. CAVERJECT is a local injection treatment; other alprostadil formulations have separate instructions.
Why dosing starts in the clinic
The response varies, so the label requires office titration and training before home use. Vial strength is not the amount every person should receive.
When an erection lasts too long
An erection lasting four hours requires urgent medical help. Repeated treatment also needs follow-up for pain, scarring or new curvature.
Model details: Alprostadil (PGE1) · relative timing
Compare timing and buildup for this compound. The values are not blood concentrations or a measure of strength.
Shows a relative timing scenario; absolute blood concentrations are not calibrated.
Timing assumptions and sources
A 1 min relative timing assumption is an upper boundary of the reported rapid IV metabolic half-life, not a measured intracavernosal tissue half-life or erection duration.
One 1 mg input peaks at 1 relative unit after a single dose. Other amounts scale proportionally; overlapping doses add when accumulation is on. Different compounds use separate relative scales.
- Timing half-life used
- 0.01666667 hours
- Absorption half-life assumed
- 0.004166667 hours
- Reference amount for the relative scale
- 1 mg
- Absorption half-life is assumed to be one quarter of the slower timescale (0.004166666666666667 h); it is not a measured absorption parameter.
- A single 1-unit input has a peak of 1 relative unit; scaling and repeated-dose addition are mathematical assumptions. This normalization is independent of the example dose.
- Never use endogenous baseline 96 pg/mL as a dose-derived peak.
- A relative systemic timing illustration does not model local tissue exposure or erection duration.
- The route extrapolation must be explicit.
- CAVERJECT US label 12.3
After 20 µg intracavernosal dosing, peripheral PGE1 at 30/60 min was 89/102 pg/mL versus baseline 96 pg/mL, without a significant increase. Absolute availability was not determined; about 80% of IV drug is metabolized in one pulmonary pass.
- CAVERJECT product information, PK
The product information reports an IV metabolic half-life below 1 min and distinguishes systemic from intracavernosal exposure.
alprostadil-relative-timing-2026-10 · version 1
Common questions
Does a longer erection mean it worked better?
No. The label seeks an erection suitable for intercourse lasting no longer than one hour; four hours needs urgent care.
Can alprostadil doses transfer between products?
Do not assume so. Injection and other local formulations have different strengths and instructions.
Sources Labels, studies and notes behind this guide
Catalog evidence: Human clinical trials. This describes the type of evidence, not a clinical review of every claim.
Summary and fact source checks: 2026-10-07. This records source checking, not medical review of the whole page.
Notes on the quick facts
- Goal
- Local blood-flow treatment; not a libido enhancer.
- Key trade-off
- A stronger or longer response is not always better.
- 1. Pfizer: CAVERJECT US prescribing information
Intracavernosal ED treatment, clinician titration/training, use limits, penile pain/fibrosis and urgent evaluation for erection beyond four hours. Local treatment; not a systemic concentration target.
- 2. Pfizer: CAVERJECT product information, February 2025
Singapore product information describes IV metabolic half-life below one minute and local intracavernosal exposure. Used for route-specific PK only; US label supplies clinical precautions.
- 3. CAVERJECT US label 12.3
After 20 µg intracavernosal dosing, peripheral PGE1 at 30/60 min was 89/102 pg/mL versus baseline 96 pg/mL, without a significant increase. Absolute availability was not determined; about 80% of IV drug is metabolized in one pulmonary pass.
- 4. CAVERJECT product information, PK
The product information reports an IV metabolic half-life below 1 min and distinguishes systemic from intracavernosal exposure.
Related compounds and examples
Related compounds
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Oxytocin
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