Alprostadil Urethral Suppository
By William T. Elliott, MD, FACP, and James Chan, PharmD, PhD
The fda has approved a new urethral suppository for the treatment of erectile dysfunction. The suppository contains the drug alprostadil, which has been available for several years as an intracavernous injection. The new formulation of alprostadil in a suppository form (MUSE, Vivus) offers men an alternative to injection therapy for erectile dysfunction. The name MUSE is an acronym for Medicated Urethral System for Erection. Based on the discovery that medications are absorbed through the urethra into the surrounding tissues, the MUSE system uses a plastic applicator to deposit a micro-suppository one inch into the urethra. Erection usually occurs within 5-10 minutes and lasts 30-60 minutes.1
Indications
MUSE is indicated for the treatment of erectile dysfunction.
Potential Advantages
The MUSE system offers the delivery of alprostadil by a less invasive route than intracavernous injection. Successful intercourse was reported in 65% of patients on alprostadil suppositories compared to 19% on placebo. The drug seems to be effective regardless of the cause of erectile dysfunction. Some patients who have failed prior intracavernous injection may respond to transurethral alprostadil. Fifty-eight percent of patients who considered the injection to be ineffective were reported to achieve erection sufficient for intercourse on transurethral alprostadil.1-3 Priapism and penile fibrosis were not reported.2
Potential Disadvantages
The most frequently reported side effects of alprostadil suppositories include penile pain (32%), urethral burning (13%), and testicular pain (5%). Minor urethral bleeding and spotting were reported in 5% of patients. The percentage of successful intercourse reported by MUSE users appears to be lower than that reported for intracavernous injections of alprostadil4,5 (> 80% vs 65%), although there are no head-to-head studies. Mild vaginal itching or burning have also been reported in women whose partner uses MUSE. The product is not recommended for use during sexual intercourse during pregnancy unless a condom barrier is used.
Some patients may find intraurethral insertion uncomfortable. The patient is advised to sit, stand, or walk for about 10 minutes after insertion of the suppository to allow for erection to develop.
Dosage Form
MUSE is available in urethral suppositories 125 mcg, 250 mcg, 500 mcg, and 1000 mcg. These dosages are significantly higher than the intracavernous injections of 10-20 mcg.
Patients should be individually titrated to the lowest dose that is sufficient for sexual intercourse. Doses of 125 or 250 mcg are recommended for initial dosing. If necessary, the dose should be increased or decreased on separate occasions in a stepwise manner until an erection sufficient for intercourse is achieved. In a small, double-blind trial, the percentages of patients who had intercourse at each dose of alprostadil were 39.4% at 125 mcg, 33.3% at 250 mcg, 40% at 500 mcg, and 50% at 1000 mcg.6 MUSE should not be used more than twice a day.
It is recommended that MUSE be stored in a refrigerator. When traveling, storage in a portable ice pack or cooler is recommended. It may be kept at room temperature for up to 14 days.
Comments
MUSE provides an alternative delivery system for alprostadil. Until now, alprostadil had been administered only by intracavernous injection, a delivery system that is unsuitable for some men.
The onset of action of the urethral suppositories is 5-10 minutes after administration, with a duration of action of 30-60 minutes in those who reported successful sexual intercourse. This is similar to the onset and duration of the injectable form.
The wholesale cost of the drug is $15-18 per dose, compared to Caverject at $14-18.
References
1. MUSE product information. Vivus; November 1996.
2. Padma-Nathan H, et al. N Engl J Med 1997;336:1-7.
3. McVary KT, et al. Abstract, VII World Meeting on Impotence; November 5, 1996.
4. Caverject product information. Pharmacia Upjohn; July 1995.
5. Linet OL, et al. N Engl J Med 1996;334:873-877.
6. Hellstrom WJG, et al. Urology 1996;48:851-856.
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