Why would someone use this instead of a tablet?

Because the tablets rely on a nerve signal that is absent or too weak in some people, particularly after certain prostate operations. Alprostadil acts on the blood vessels directly, so it does not depend on that signal.

Is the injection self-administered?

After training, yes, and the label describes the technique. The first administration is normally supervised by a clinician.

What is a prolonged erection warning?

The label carries a warning about erections lasting beyond a stated number of hours, which is a medical emergency because the blood in the penis stops being oxygenated. The threshold and the instruction are in the label section on this page.

Alprostadil

The option for people the tablets do not work for, given as a pellet into the urethra or an injection rather than swallowed.

Prescription onlyHow to get it legally

Class: Prostaglandin E1
Sold as: Muse, Caverject, Vitaros
approved labels read: 1

On this page

From the approved label

FDA · EN

Caverject

Approved uses: For the treatment of erectile dysfunction.
As an adjunct to other diagnostic tests in the diagnosis of erectile dysfunction
Forms and strengths: For injection: 20 mcg/vial and 40 mcg/vial lyophilized powder in single-dose vials for reconstitution.
How it is taken: Determine the most suitable dose and presentation of CAVERJECT to use. Use a new vial for each dose of CAVERJECT.
Administer first intracavernosal injections in the health care provider's office and titrate the dose for each patient to the lowest effective dose.
Instruct the patient on proper use and assess that they are well trained in the self-injection technique prior to initiation of at-home use.
Recommended dosage for erectile dysfunction:
Erectile dysfunction of vasculogenic, psychogenic, or mixed etiology: Initiate dosing with 2.5 mcg
Erectile dysfunction of pure neurogenic etiology (spinal cord injury): Initiate dosing with 1.25 mcg
Must not be used when: Men who have known hypersensitivity to the drug.
Men who have conditions that predispose them to priapism, such as sickle cell anemia or sickle cell trait, multiple myeloma, or leukemia.
Treatment of erectile dysfunction in men with fibrotic conditions of the penis, such as anatomical deformation, angulation, cavernosal fibrosis, or Peyronie's disease.
Men with penile implants.
Interactions: The potential for pharmacokinetic drug-drug interactions between alprostadil and other agents administered orally or intracavernosally has not been formally studied.
Warnings and precautions: Prolonged erection and priapism have occurred in patients receiving CAVERJECT. To minimize the chances of this occurring, titrate CAVERJECT slowly to the lowest effective dose
Penile fibrosis has occurred in patients receiving CAVERJECT. Follow patients regularly to detect signs of penile fibrosis. Discontinue in patients who develop penile angulation or cavernosal fibrosis.
Hypotension: Injections of CAVERJECT can lead to increased peripheral blood levels of alprostadil, especially in patients with significant corpora cavernosa venous leakage. Avoid use in patients with known cavernosal venous leakage.
Injection site bleeding may occur in patients taking anticoagulants, such as warfarin or heparin. Compress the site of injection with an alcohol swab or sterile gauze for 5 minutes.
Cardiovascular risk related to underlying medical conditions: Underlying treatable medical causes of erectile dysfunction should be diagnosed and treated prior to initiation of therapy.
Risks of use in combination with other vasoactive medications injected intracavernosally: Safety and efficacy of combinations of CAVERJECT and other vasoactive agents have not been systematically studied. Use of such combinations is not recommended.
Needle breakage: A superfine needle is used for administration of CAVERJECT and cases of needle breakage have been reported. Careful instruction in proper patient handling and injection techniques may minimize this risk.
Benzyl alcohol: Serious and fatal adverse reactions can occur in neonates and low birth weight infants treated with benzyl alcohol-preserved formulations in infusion solutions, including CAVERJECT. CAVERJECT is not indicated in neonates and infants.
Common side effects: Most common (≥10%) adverse reaction is penile pain.
Pregnancy: CAVERJECT is not indicated for use in females.
How it acts: Alprostadil (PGE1) is a prostaglandin with a wide variety of pharmacological actions including vasodilation and inhibition of platelet aggregation. Alprostadil induces erection by relaxation of trabecular smooth muscle and by dilation of cavernosal arteries by binding to its receptors and increasing intracellular cyclic adenosine monophosphate (cAMP) levels via modulation of adenylate cyclase. This leads to expansion of lacunar spaces and entrapment of blood by compressing the venules against the tunica albuginea, a process referred to as the corporal veno-occlusive mechanism.

This section reports the approved product information. The wording is condensed from the regulator's own summary, and the full document is linked under Sources.

Written by us

How it works

Alprostadil is not a PDE5 inhibitor and does not depend on the nerve signal those drugs extend. It relaxes the blood vessels of the penis directly, which is why it can work when the tablets do not, including after prostate surgery where the nerves involved have been damaged. Delivering it means either a small pellet placed in the urethra or an injection into the side of the penis, both of which are taught by a clinician the first time.

Original and generic

The brands differ by delivery method rather than by substance: a urethral pellet, an injection, and in some European countries a cream. Generic versions of the injection exist. This is not a category where a cheaper equivalent tablet is available, because there is no tablet.

What it costs

More expensive per use than any of the tablets, and in several European health systems it is reimbursed for specific indications such as after prostate surgery, which changes the arithmetic considerably. Pricing outside reimbursement varies too much between countries to summarise usefully.

How to get it legally

Prescription only, and this is the one option in the category where an in-person appointment is genuinely the norm rather than a formality: the first dose is usually given under supervision so the technique and the response can be observed. Online clinics do not typically start treatment with it.

Questions

Why would someone use this instead of a tablet?: Because the tablets rely on a nerve signal that is absent or too weak in some people, particularly after certain prostate operations. Alprostadil acts on the blood vessels directly, so it does not depend on that signal.
Is the injection self-administered?: After training, yes, and the label describes the technique. The first administration is normally supervised by a clinician.
What is a prolonged erection warning?: The label carries a warning about erections lasting beyond a stated number of hours, which is a medical emergency because the blood in the penis stops being oxygenated. The threshold and the instruction are in the label section on this page.

Sources

Caverject: prescribing informationDailyMed, US National Library of Medicine. Label version 13 May 2024
Drugs@FDA: NDA020379US Food and Drug Administration