# ED injections and urethral suppositories: alprostadil, Trimix and MUSE > ED injections place a medicine called alprostadil, or a compounded mixture often called Trimix, directly into the penis to widen its blood vessels. MUSE delivers alprostadil as a tiny pellet in the urethra. Alprostadil injections and MUSE are FDA-approved. Trimix is compounded, not FDA-approved. Each starts with an in-office test, and a prolonged erection is the most serious risk of injections. _Last updated: 2026-10-17_ --- **In short:** when pills are ruled out, do not work well enough, or are simply not a man's preference, there are two medicine routes that act on the penis directly. One is an injection into the erectile tissue. The other is a tiny medicated pellet placed in the urethra, sold as MUSE. Both rely on the same FDA-approved drug, alprostadil, and the injection route also includes pharmacy-compounded mixtures, often called Trimix, that are not FDA-approved. This page explains how each works, what the labels and the American Urological Association (AUA) guideline say, and what the main risks are. It leaves out doses, mixtures and technique on purpose: those are set in the clinic, for one person, after an in-office test. ## What are ED injections and urethral suppositories? They are prescription treatments that deliver an erection-producing medicine straight to the penis instead of through the bloodstream from a pill. NIDDK says injectable medicines and suppositories "can enhance erections," that an injectable medicine "causes a quick, automatic erection by increasing blood flow to the penis," and that a health care professional will teach you how to give yourself an injection or insert a suppository ([NIDDK, Treatment for ED](https://www.niddk.nih.gov/health-information/urologic-diseases/erectile-dysfunction/treatment)). The AUA guideline says men with ED should be told about both options, including their benefits and burdens (Statements 14 and 16) ([AUA Erectile Dysfunction Guideline](https://www.auanet.org/guidelines-and-quality/guidelines/erectile-dysfunction-%28ed%29-guideline)). | Option | What it is | FDA status | | ---------------------------------------------- | ------------------------------------------------------------------------------------------- | ----------------------------------------- | | Alprostadil injection (Caverject, Edex) | Alprostadil injected into the erectile tissue of the penis | FDA-approved prescription medicine for ED | | Compounded injection mixtures (such as Trimix) | Combinations of drugs such as papaverine, phentolamine and alprostadil, mixed by a pharmacy | Compounded: not FDA-approved | | Intraurethral alprostadil (MUSE) | A small alprostadil pellet placed in the urethra with an applicator | FDA-approved prescription medicine for ED | Sources: [Caverject](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a295fc1e-d82c-4f44-bc2d-a552bf594c98) and [Edex](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e8b8ec8d-1318-43e4-a182-446e9f9579de) prescribing information, DailyMed; [MUSE prescribing information, FDA](https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/020700s032lbl.pdf); [AUA Erectile Dysfunction Guideline](https://www.auanet.org/guidelines-and-quality/guidelines/erectile-dysfunction-%28ed%29-guideline), Statement 16 discussion. For where these sit among every other option, see our overview of [ED treatment options beyond pills](/ed-treatment-options/). ## How do ED injections work? An ED injection works on the blood vessels and smooth muscle inside the penis itself, so it does not depend on the chain of signals that a pill strengthens. The Caverject label describes alprostadil as a synthetic form of prostaglandin E1 that "induces erection by relaxation of trabecular smooth muscle and by dilation of cavernosal arteries." Blood flows in, the spongy erectile spaces expand, and they press the small outflow veins shut against the tissue that surrounds them, which traps the blood and holds the erection ([Caverject prescribing information, sections 11 and 12.1, DailyMed](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a295fc1e-d82c-4f44-bc2d-a552bf594c98)). The AUA guideline names four substances commonly used for injection: alprostadil, papaverine, phentolamine and atropine. It also explains why some men use them. Injections can suit men who cannot take a PDE5 inhibitor such as sildenafil, men who prefer not to take an oral medicine, and men who find pills inadequate; the guideline notes that PDE5 inhibitors are ineffective in about 40% of men, and that some men who respond at first stop responding as ED progresses. It adds that injections have been reported to work in diverse groups, including men with diabetes, men after prostate removal and men with spinal cord injuries ([AUA Erectile Dysfunction Guideline, Statement 16](https://www.auanet.org/guidelines-and-quality/guidelines/erectile-dysfunction-%28ed%29-guideline)). How pills work, for comparison, is covered in [how ED medications work](/how-ed-medications-work/), and the specific case of recovery after surgery or radiation is in [ED after prostate treatment](/ed-after-prostate-treatment/). ## Which ED injections are FDA-approved? Status: FDA-approved prescription medicine for ED. Source: Caverject and Edex prescribing information, DailyMed, checked 2026-10-17. Alprostadil is the only injected ED medicine with FDA approval. The AUA guideline states: "Only alprostadil is FDA-approved in the U.S. for ICI injection, and it is the only medication typically used as a single agent" ([AUA Erectile Dysfunction Guideline, Statement 16](https://www.auanet.org/guidelines-and-quality/guidelines/erectile-dysfunction-%28ed%29-guideline)). Two branded products appear on DailyMed. Caverject "is indicated for the treatment of erectile dysfunction" and also as an add-on to other tests used to diagnose ED ([Caverject prescribing information, section 1, DailyMed](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a295fc1e-d82c-4f44-bc2d-a552bf594c98)). Edex is indicated for ED "due to neurogenic, vasculogenic, psychogenic, or mixed etiology," meaning nerve, blood-vessel, psychological or mixed causes ([Edex prescribing information, DailyMed](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e8b8ec8d-1318-43e4-a182-446e9f9579de)). Both labels make the clinic part of the treatment. Caverject's label says the first injections are given in the health care provider's office by medically trained personnel, that patients must be "well trained in the self-injection technique" before using it at home, and that patients should be re-evaluated regularly. The Edex label says "the desirable dose should be established in the physician's office" and that the patient "must visit the physician's office for regular checkups." ## Is Trimix FDA-approved? Status: Compounded: not FDA-approved. Source: AUA Erectile Dysfunction Guideline and FDA Compounding Q&A, checked 2026-10-17. No. Trimix is not an FDA-approved product. It is a name used for pharmacy-made injection mixtures; the AUA guideline lists alprostadil plus papaverine plus phentolamine among the combinations in use, and a 2024 review of injection therapy says prostaglandin E1 (alprostadil) and "trimixes" continue to be the agents of choice ([Porst et al., Sex Med Rev 2024](https://pubmed.ncbi.nlm.nih.gov/38644056/)). The guideline is direct about their status: "there are no combination ICI drugs currently approved by the FDA," "no standardized mixture is approved by the FDA," and "these combinations must be compounded by the pharmacy based on physician instructions." It also says men should be told that injectable non-prostaglandin agents, such as papaverine and phentolamine, are not formally FDA-approved for ED, even though they have been used for decades ([AUA Erectile Dysfunction Guideline, Statements 16 and 17](https://www.auanet.org/guidelines-and-quality/guidelines/erectile-dysfunction-%28ed%29-guideline)). What "compounded" means matters. The FDA says compounded drugs "are not FDA-approved," which means the agency "does not verify the safety, effectiveness or quality of compounded drugs before they are marketed," and that they should only be used in patients whose medical needs cannot be met by an FDA-approved drug ([FDA, Compounding and the FDA: Questions and Answers](https://www.fda.gov/drugs/human-drug-compounding/compounding-and-fda-questions-and-answers)). The AUA notes that cost can differ a great deal between brand-name and compounded medicines, and that cost belongs in the conversation about which medicine to use. The Caverject label adds a caution of its own: the safety and effectiveness of combining Caverject with other injected vasoactive drugs "have not been established in clinical studies," and the risks of prolonged erection, priapism and low blood pressure "may be increased" ([Caverject prescribing information, section 5.6, DailyMed](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a295fc1e-d82c-4f44-bc2d-a552bf594c98)). For how compounded products differ from approved generics and counterfeits, see [are generic ED medications safe?](/are-generic-ed-medications-safe/) ## What is the in-office test? The in-office test is a supervised first use, in the clinic, before a man treats himself at home. The AUA guideline makes it a clinical principle for both routes: "an in-office injection test should be performed" for men considering injections (Statement 17), and "an in-office test should be performed" for men considering intraurethral alprostadil (Statement 15) ([AUA Erectile Dysfunction Guideline](https://www.auanet.org/guidelines-and-quality/guidelines/erectile-dysfunction-%28ed%29-guideline)). According to the guideline, the injection test has several jobs: finding the medicine or mixture and the dose that produce a long enough response with acceptable side effects, building confidence with the technique, and teaching the man and his partner how the dose is adjusted, why the injection site is alternated, and what to do if an erection lasts too long. It says finding the right drug and dose "may take several visits," and that all of this education should be documented. The Caverject label adds that a man stays in the office until the erection has gone down ([Caverject prescribing information, section 2.2, DailyMed](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a295fc1e-d82c-4f44-bc2d-a552bf594c98)). An injection test is also one of the specialized tests sometimes used to diagnose ED, which we cover in [how ED is diagnosed](/how-ed-is-diagnosed/). ## What is MUSE? Status: FDA-approved prescription medicine for ED. Source: MUSE prescribing information, FDA, checked 2026-10-17. MUSE is alprostadil given as a urethral suppository instead of an injection. The label describes "a single-dose, medicated transurethral system": a medicated pellet, 1.4 mm across, that sits in the tip of a hollow applicator, which is inserted into the urethra after urinating and releases the pellet when its button is pressed ([MUSE prescribing information, FDA](https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/020700s032lbl.pdf)). The label explains that the drug is absorbed from the urethra and carried into the erectile tissue through connecting blood vessels, where it widens the arteries and relaxes the smooth muscle much as the injected form does. The AUA describes intraurethral alprostadil as an option for men who cannot take PDE5 inhibitors, for men or partners who would rather avoid oral medication, and for men or partners who "prefer not to use the needles required for ICI medications" (Statement 14). The MUSE label says the first dosing is done under a physician's supervision, both to test a man's response and to watch for low blood pressure: symptomatic low blood pressure occurred during in-clinic dosing in 3% of patients, with fainting in 0.4%. It also says MUSE should not be used for sex with a pregnant partner unless a condom is used. ## How well do injections and MUSE work? Both work for many men in studies, and injections generally work better than the urethral route. The AUA guideline reports that, across injection studies, the share of men who achieved an erection sufficient for intercourse ranged from 53.7% to 100%, without marked differences between medicines or mixtures; it also warns that more than 90% of those study arms were observational, the weakest design. Satisfaction ranged from 46.3% to 98.8%, lowest with papaverine ([AUA Erectile Dysfunction Guideline, Statement 16](https://www.auanet.org/guidelines-and-quality/guidelines/erectile-dysfunction-%28ed%29-guideline)). On the labels, in an Edex study, 141 men went on from a dose-finding phase to a placebo-controlled phase; 73% of them had an erection sufficient for intercourse after the injection, compared with 13% after placebo ([Edex prescribing information, DailyMed](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e8b8ec8d-1318-43e4-a182-446e9f9579de)). For the urethral route, the guideline gives a more cautious picture. In the largest study, 995 of 1,511 men (65.8%) responded in the office, and of the 461 then assigned to alprostadil, 299 (64.9%) had intercourse at least once at home. The guideline's conclusion: "a positive in-office test does not guarantee efficacy in the home environment," and men should be counseled that the urethral approach "is generally less effective than the ICI approach" ([AUA Erectile Dysfunction Guideline, Statement 14](https://www.auanet.org/guidelines-and-quality/guidelines/erectile-dysfunction-%28ed%29-guideline)). These are group results from studies, not a prediction for any one man. ## What is the priapism risk? A prolonged erection is the most serious risk of injections, and both labels and the guideline treat it as something to plan for from day one. The AUA calls priapism "the most serious AE associated with ICI medications," and reports the lowest priapism rates, a mean of 1.8%, in studies of alprostadil used alone, alongside a mean 6.3% rate of prolonged or painful erections in those studies ([AUA Erectile Dysfunction Guideline, Statement 16](https://www.auanet.org/guidelines-and-quality/guidelines/erectile-dysfunction-%28ed%29-guideline)). | Treatment | What the label reports | | ------------------- | -------------------------------------------------------------------------------------------------------------------------- | | Caverject injection | Prolonged erection (4 to 6 hours) in 4% of 1,861 patients treated up to 18 months; priapism (more than 6 hours) in 0.4% | | Edex injection | Prolonged erection (more than 4 hours) in 4% of patients treated up to 24 months; priapism (more than 6 hours) in under 1% | | MUSE suppository | Priapism (4 hours or longer) in 2 of 1,511 patients (0.13%) in two placebo-controlled studies | Sources: [Caverject, section 5.1](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a295fc1e-d82c-4f44-bc2d-a552bf594c98) and [Edex](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e8b8ec8d-1318-43e4-a182-446e9f9579de) prescribing information, DailyMed; [MUSE prescribing information, FDA](https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/020700s032lbl.pdf). The studies and definitions differ, so the rows are not directly comparable. The Caverject label says that if priapism "is not treated immediately, penile tissue damage and permanent loss of potency may result," and the guideline says that finding the right dose and teaching the man how it is adjusted is "critical to minimize the risk of priapism" whatever medicine is used. Our [priapism guide](/priapism/) explains why it is an emergency and what happens at the hospital. Get medical help right away. The Caverject label tells patients to seek immediate medical assistance for an erection that persists longer than 4 hours, and NIDDK lists erections lasting longer than 4 hours among the side effects of ED medicines taken by mouth, by injection or as a suppository. Follow the plan your prescriber gave you at the in-office test, and do not wait to see whether it settles. ## What other side effects do the labels list? Pain is the most common one. The Caverject label lists penile pain in 37% of patients in studies of up to 18 months, mostly mild or moderate, with 3% stopping treatment because of it; it also lists penile fibrosis (scarring) and injection-site hematoma in 3% each, and bruising in 2% ([Caverject prescribing information, section 6.1, DailyMed](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a295fc1e-d82c-4f44-bc2d-a552bf594c98)). The Edex label reports an overall penile fibrosis rate, including Peyronie's disease, of 7.8% in studies of up to 24 months ([Edex prescribing information, DailyMed](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e8b8ec8d-1318-43e4-a182-446e9f9579de)). | Side effect | Injections (labels) | MUSE (label) | | --------------------- | ------------------------------------------------------ | ------------------------------------------------------------ | | Pain | Penile pain in 37% (Caverject) | Penile pain in 32%, versus 3% on placebo | | Scarring or curvature | Penile fibrosis in 3% (Caverject) and 7.8% (Edex) | Not in the label's common-reaction table | | Bleeding | Injection-site hematoma 3% and bruising 2% (Caverject) | Minor urethral bleeding or spotting in 5%, versus 1% | | Other local effects | Penile rash and swelling, 1% each (Caverject) | Urethral burning 12% and testicular pain 5% | | Low blood pressure | Possible; listed as a warning | Symptomatic low blood pressure in 3% during in-clinic dosing | | Partner | Not applicable | Vaginal burning or itching in 5.8% of partners, versus 0.8% | Sources: [Caverject, sections 5 and 6](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a295fc1e-d82c-4f44-bc2d-a552bf594c98) and [Edex](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e8b8ec8d-1318-43e4-a182-446e9f9579de) prescribing information, DailyMed; [MUSE prescribing information, FDA](https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/020700s032lbl.pdf). Two injection-specific warnings are worth knowing. The Caverject label says needle breakage, with part of the needle left in the penis, has been reported and has sometimes needed surgery to remove, and that men on blood thinners such as warfarin or heparin may bleed more at the injection site. The AUA suggests documenting any existing curvature or scarring before injections start and checking regularly for new changes, and both injection labels say treatment should stop if angulation or fibrosis develops. Curvature from scarring is covered on our [Peyronie's disease](/peyronies-disease/) page. None of these treatments protects against sexually transmitted infections, which all three labels state. ## Who should not use these treatments? The labels list conditions in which they should not be used. Caverject and Edex should not be used by men with conditions that make priapism more likely, such as sickle cell anemia or sickle cell trait, multiple myeloma or leukemia, by men with fibrotic conditions of the penis such as Peyronie's disease, or by men with [penile implants](/penile-implant/) ([Caverject, section 4](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a295fc1e-d82c-4f44-bc2d-a552bf594c98); [Edex](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e8b8ec8d-1318-43e4-a182-446e9f9579de), DailyMed). MUSE should not be used by men with urethral stricture, inflammation or infection of the urethra or the head of the penis, severe hypospadias or curvature, or blood conditions that raise the risk of clots or priapism, such as sickle cell anemia or trait, thrombocythemia, polycythemia or multiple myeloma ([MUSE prescribing information, FDA](https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/020700s032lbl.pdf)). All three labels also say these treatments should not be used by men for whom sexual activity is inadvisable; the two injection labels link this to heart health. Having a condition on these lists is a reason to talk through the options with a prescriber. Injections and MUSE are started only by a prescriber, after an in-office test. Before that visit, it helps to note any blood condition such as sickle cell disease or trait, any curve or lump in the penis, any blood-thinning or blood pressure medicine, any heart condition, and any erection that has ever lasted too long. After starting, report new pain, a new lump or hard area, or a new curve to the prescriber promptly, as the labels advise. Our guide on [when to see a doctor about ED](/when-to-see-a-doctor-about-ed/) covers the conversation itself. ## Sources 1. [Caverject (alprostadil) for injection, prescribing information and patient information, revised March 2023, DailyMed](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=a295fc1e-d82c-4f44-bc2d-a552bf594c98) 2. [Edex (alprostadil for injection) prescribing information, revised March 2024, DailyMed](https://dailymed.nlm.nih.gov/dailymed/drugInfo.cfm?setid=e8b8ec8d-1318-43e4-a182-446e9f9579de) 3. [MUSE (alprostadil) urethral suppository prescribing information, revised May 2024, FDA](https://www.accessdata.fda.gov/drugsatfda_docs/label/2024/020700s032lbl.pdf) 4. [Burnett AL, Nehra A, Breau RH, et al. Erectile Dysfunction: AUA Guideline. J Urol 2018;200:633. Statements 14 to 17 and discussion. American Urological Association](https://www.auanet.org/guidelines-and-quality/guidelines/erectile-dysfunction-%28ed%29-guideline) 5. [FDA. Compounding and the FDA: Questions and Answers](https://www.fda.gov/drugs/human-drug-compounding/compounding-and-fda-questions-and-answers) 6. [NIDDK. Treatment for Erectile Dysfunction, last reviewed October 2024](https://www.niddk.nih.gov/health-information/urologic-diseases/erectile-dysfunction/treatment) 7. [Porst H, Lewis R, Virag R, Goldstein I. A comprehensive history of injection therapy for erectile dysfunction, 1982-2023. Sex Med Rev. 2024 (abstract, PubMed)](https://pubmed.ncbi.nlm.nih.gov/38644056/) --- _Affiliate disclosure: some links on the web version of this site go to Bodybuilding Peptides (trybbpeptides.com), an affiliate destination, and we may earn a commission if you buy there. Our coverage is independent of that relationship. Details: https://theedreport.com/affiliate-disclosure/_