MEDICATED URETHRAL SYSTEM FOR ERECTION (MUSE)


MUSE is short for "medicated urethral system for erection." It consists of a tiny medicated pellet that is inserted into the urethra, the opening at the end of the penis, to produce erections.

Administration of the drug alprostadil through the urethra using the MUSE system is an effective alternative treatment for many men, and provides a less invasive alternative to intrapenile injection.

Alprostadil is a prostaglandin E preparation in a pellet form that is inserted with a plunger-like mechanism into the urethral opening. The plunger device is a thin plastic tube with a button at the top.

Plunger
The plunger device is pre-filled to deliver a pellet about an inch deep into the urethra at the tip of the penis.

The active ingredient is alprostadil (PGE1). Alprostadil assists in causing relaxation of cavernosal smooth muscle and dilatation of cavernosal arterioles. These actions permit increased penile blood flow and address secondary veno-occlusive mechanism by compression of the venules against the surrounding tunica albuginea.

Alprostadil is a form of a natural substance, prostaglandin E1, which serves to open blood vessels. It is effective in men with a wide range of medical disorders, including diabetes, surgery, and injury. It does not work in those with severe circulatory or nerve damage.

Prostaglandin E1 raises the intracellular concentration of the cyclic AMP, which leads to relaxation of the cavernosal smooth muscle, increase of arterial blood flow, dilation of sinusoids and veno-occlusion, thanks to the compression of sub-tunica albuginea venules against the tunica albuginea. Evidently, the attempt to use this drug transurethrally with no need for a penile injection is very appealing. Despite the existence of submucous veins that communicates the corpus spongiosum and the corpora cavernosa, therefore creating a possible absorption means, this procedure is considered erratic, meaning there is no constant correlation between given drug dose and absorbed dose. That may explain reports from patients stating that neither priapism nor any response at all was mentioned, upon the same transurethral alprostadil dose

Method
Men should be advised to urinate before insertion, because lubricants should not be used and a moist urethra will allow for easier insertion of the plunger device.


This illustration shows how the applicator is inserted into the opening at the end of the penis to leave the small pellet.

Right after you urinate, insert the tube into the urethral opening and press the button. A pellet containing the drug is released. After insertion, the pellet within the urethra should be dissolved by massaging or "kneading" the penis for about a minute. To avoid discomfort, keep the penis as straight as possible during administration. Roll the penis between his hands for 10 to 30 seconds to evenly distribute the drug. Urinating or urine leakage right after administration may reduce the amount of medication. If you lie on your back too soon after administration, blood flow to the penis may decrease and the erection may be lost. You should be upright, either sitting, standing or walking for about 10 minutes after administration. By that time, you should have achieved an erection that lasts between 30 to 60 minutes. The erection may continue after orgasm.

It is not recommended for use more than once in a twenty-four-hour period.

Patients also find that it works better with a ring-type device to prevent the drug from getting absorbed into the systemic circulation. Moreover, since venous drainage problems may thwart the erection being caused by alprostadil insertion by premature drainage, the ring at the base of the penis helps to constrict venous outflow

The first application (usually a 500-g dose) should be undertaken in the physician's office because of the potential complications of urethral bleeding, vasovagal reflex, hypotension, and priapism. Depending on the erectile response, you may then be instructed to increase or decrease the dose (up to 1000 g or down to 250 g).

There are currently four dosage strengths available: 125, 250, 500, and 1,000 mcg; the dose is based on the response.

The MUSE system should not be used more than twice a day.

Side Effects
The side effects of the drug itself are the same whether the drug is administered by injection or through the urethra, although each method has other side effects that are specific to it. Priapism (prolonged erection) is a potential side effect for both forms of administration although there is less chance for it using the MUSE system. If this occurs, applying ice for ten-minute periods to the inner thigh may help reduce blood flow. Erections that last four hours or longer require emergency care. Scarring of the penis (Peyronie's disease) is also possible with both treatments, although the chances are far less with the MUSE system.

About 10% to 17% of MUSE administrations result in a burning sensation in the urethra that can last five to fifteen minutes, but this moderate pain does not appear to be a main reason for discontinuing treatment. Some pain in the penis occurs in about 29% of cases; it is usually mild. About 3% of patients experience low blood pressure. Other side effects include minor bleeding or spotting, redness in the penis, and aching in testicles, legs, and area around the anus; warmth or burning sensation in the urethra; redness of the penis due to increased blood flow; and minor urethral bleeding or spotting.

Men with or at risk for blood clots or who are using blood thinners, such as heparin or warfarin, should not use it. It is not appropriate for men with penile implants.

Sudden low blood pressure can occur. Up to 50% of patients have a measurable drop in blood pressure, although only about 3% are aware of it. Some patients have significant symptoms of hypotension Symptoms include dizziness, lightheadedness, and fainting. If these symptoms occur, the man should lie down immediately with his legs raised. The drug may have toxic effects if it reaches the fetus in pregnant women; men should not use alprostadil, then, for intercourse with pregnant women without the use of a condom or other barrier contraceptive device.

Women partners may experience vaginal burning or itching.

One of the more unusual side effects involved a case where the MUSE pellet became caught in a female partner's mouth during oral sex and created an allergic reaction which necessitated a trip to the emergency room. For this reason, oral sex is not recommended when using the MUSE system.

Contra-Indications
Contraindications include usage with a pregnant partner or a partner who is likely to get pregnant, hypersensitivity to prostaglandin, and sickle cell anemia, or a patient who is prone to developing priapism.

MUSE is not appropriate for men with abnormal penal anatomy. Taking certain cold and allergy remedies may offset the effects of the MUSE-administered drug

Efficacy
The Medicated Urethral System for Erection study group -( M.U.S.E.) have mentioned good results with the use of transurethral alprostadil, in a pioneer study; 64,9% of patients had sexual intercourse at home, regardless of impotence etiology and their age, with only 5,1% of discreet urethral traumas. However, 32,7% of the patients mentioned pain after the transurethral application. More recently, Porst reported that 43% of patients treated with 1000mcg of transurethral alprostadil were able to have a sexual intercourse, but only 10% mentioned rigid erection. Similarly, Werthmam and Rajfer obtained 30% of erections that enabled vaginal penetration, but only 7% of 100 patients using up to 1000mcg of alprostadil mentioned rigid erections.

In another study, the efficacy of intraurethral alprostadil was evaluated in a double-blind, placebo-controlled trial in 1511 men with chronic erectile dysfunction from a variety of organic causes. Two-third of these men responded to intraurethral alprostadil with an erection sufficient for intercourse in the clinic; these men were then randomly assigned to therapy with either alprostadil or placebo. Successful intercourse on at least one occasion was much more likely with alprostadil (65 versus 19 percent with placebo). Among the men who responded to alprostadil, 7 of 10 applications were followed by successful intercourse.

In one study, 65% of men achieved erection using MUSE, and these men achieved intercourse in an average of 7 out of 10 administrations. A more recent study, however, reported disappointing results, with only 27% achieving erections and only 18% requesting additional refills.