Individuals at higher risk for priapism (painful erection lasting longer than six hours), including men with sickle cell anemia, thrombocytopenia (low platelet count), polycythemia (increased red blood cell count), multiple myeloma (a cancer of the white blood cells), and history of blood clots (for example, deep venous thrombosis [DVT]) or hyperviscosity (thick blood) syndrome are at increased risk for priapism with MUSE.
In patients with low testosterone, testosterone treatment can improve libido and erectile dysfunction, but many men still may need additional oral medications such as sildenafil, vardenafil, or tadalafil. Some studies suggest that men with ED and low testosterone may respond better to PDE5 inhibitors when given testosterone therapy; however, this is controversial.
Intraurethral therapy (Medicated Urethral System for Erections, or MUSE): Alprostadil (PGE1) has been formulated into a small suppository that can be inserted into the urethra (the canal through which urine and semen are excreted). The suppository is preloaded into a small applicator and by placing the applicator into the tip of the penis and compressing the button at the other end of the applicator and wiggling the applicator, the suppository is released into the urethra. Gentle rubbing/massaging of the penis will cause the suppository to dissolve and the medication is absorbed through the urethra and passes into the penis where it stimulates the relaxation of the muscle in the arteries and increases blood flow to the penis. It takes 15 to 30 minutes for this to occur. Success rates in the clinical studies were noted to be about 65%, however lower rates were noted when it started being used in the real world setting. This drug may be effective in men with vascular disease, diabetes, and following prostate surgery. This is a useful alternative for men who do not want to use self-injections or for men in whom oral medications have failed. Few side effects occur. The most common side effect is penile pain, which can vary from minor to uncomfortable. MUSE use has been associated with lowering of the blood pressure and thus it is recommended that the first time using the MUSE be in the physician's office so that you can be monitored. One cannot use lubricants of any type to help with the insertion of the applicator thus to make it easier to insert you should urinate immediately before using the MUSE system as this will lubricate the urethra. A temporary tourniquet is often helpful in allowing the medication to stay in the erectile tissue a little longer and seems to give a somewhat better response.
Finally, gene therapy and stem cell research has widened the frontier of ED treatment proposed as possibility to even reverse ED. Specifically, gene therapy pertains to repairing the cause of ED by restoring defective gene function and/or altering the expression of the mutant gene (32). Most of the available data on gene therapy are in the animal model. However, a phase I clinical trial in men with ED undergoing intracavernous injection with a DNA plasmid carrying the alpha-subunit of the corporal smooth muscle Maxi-K channel showed promise in increased erectile function based on IIEF assessment sustained throughout the 3-month study period (122).
The availability of phosphodiesterase-5 (PDE5) inhibitors—sildenafil, vardenafil, tadalafil, and avanafil—has fundamentally altered the medical management of ED. In addition, direct-to-consumer marketing of these agents over the last 15 years has increased the general public’s awareness of ED as a medical condition with underlying causes and effective treatments.

Poor sleep patterns can be a contributing factor for erectile dysfunction, Mucher says. One review published in the journal Brain Research emphasized the intricate relationship between the level of sex hormones like testosterone, sexual function, and sleep, noting that testosterone levels increase with improved sleep, and lower levels are associated with sexual dysfunction. Hormone secretion is controlled by the body’s internal clock, and sleep patterns likely help the body determine when to release certain hormones. 
Nerves originating in the spinal cord and peripheral ganglia innervate the penis. There are autonomic (parasympathetic and sympathetic), and somatic separate and integrated pathways. The autonomic pathways neurons originate in the spinal cord and peripheral ganglia from the sympathetic and parasympathetic systems, respectively. They merge to form the cavernous nerves that travel alongside the prostate, enter the corpora cavernosa and corpus spongiosum to affect the neurovascular events required for tumescence and detumescence. The somatic nerves send sensory information from the penile skin, glans, and urethra via the dorsal penile nerve and pudendal nerve to the spinal cord. The somatic nerves also initiate contraction of the ischio- and bulbocavernosus muscles.
ICI therapy often produces a reliable erection, which comes down after 20-30 minutes or with climax. Since the ICI erection is not regulated by your penile nerves, you should not be surprised if the erection lasts after orgasm. The most common side effect of ICI therapy is a prolonged erection. Prolonged erections (>1 hour) can be reversed by a second injection (antidote) in the office.
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