What Medications Are Used for Erectile Dysfunction?

Overview

Erectile dysfunction (also called ED or impotence) is the inability to maintain or develop an erection. Although ED is not directly caused by prostate cancer, it can develop after many of prostate cancer’s common treatment options, including radiation therapy, surgery (such as radical prostatectomy), and hormone therapy. Different treatment options carry varying probabilities of developing ED, as well as varying statistics on the possibility of the newly developed ED reversing itself overtime. Since ED can be caused by other conditions that may enlarge the prostate, such as BPH, you will need to discuss aspects of your ED with your doctor before they can determine the best course of treatment.

While struggling with ED, many men treated for their prostate cancer may also want to pursue treatment for their ED. Thankfully, there are several treatment options on the market for ED that have been well studied and deemed effective. The two main classes of ED medications include orally administered phosphodiesterase-5 (PDE5) inhibitors and injectable or urethral suppository or pellet versions of alprostadil. Although both of these medications are very different in administration, they both share similar underlying mechanisms of action: to act as vasodilators.

Vasodilators relax smooth muscle cells allowing blood vessels to expand. When blood vessels are allowed to expand, more blood can flow to the dilated area. During the normal sexual arousal process, compounds like nitric oxide are released in the body, setting off a chain reaction of muscle relaxing events that will lead to increased blood flow to the penis, creating an erection. After prostate cancer treatment, this process can be disrupted, and may need assistance from outside medications. Vasodilators support this process in different ways to ultimately relax the smooth muscle cells around the blood vessels leading to the penis, and allow for increased blood flow to the area that will create an erection.^1,2

Oral medications for ED

The three main oral medications for ED include Viagra (sildenafil citrate), Levitra (vardenafil hydrochloride), Stendra (avanafil), and Cialis (tadalafil). All three of these are phosphodiesterase-5 (PDE5) inhibitors. PDE5 inhibitors prevent the degradation of an important component in the smooth muscle relaxation process, cGMP. CGMP relaxes the smooth muscles around the blood vessels leading to the penis during sexual arousal, allowing for a greater amount of blood flow to the area. PDE5 inhibitors cannot be used with nitrate medications as dangerous and life-threatening low blood pressure can occur. The dosage of these medications depends on the specific type used, but all are indicated for use only once a day at most.^3-5

Common side effects of PDE5 inhibitors include:

• Nasal congestion
• Back pain
• Muscle pain
• Gastrointestinal distress or upset stomach
• Flushing
• Headache
• Nausea
• Rash
• Dizziness

This is not a complete list of all side effects of PDE5 inhibitors. Your provider will help you determine if there are any additional side effects that you may be at risk for. There are more serious side effects of PDE5 inhibitors that individual’s taking these medications that require immediate medical attention, including:

• Fainting
• Decreased blood pressure
• Erection lasting longer than 4 hours
• Sudden loss of vision in one or both eyes
• Sudden loss of hearing in one or both ears
• Cardiovascular complications, including heart attack, or stroke
• Signs of an allergic reaction including chest pain, difficulty breathing, or fever

Alprostadil

Although different in the way it’s administered, alprostadil-containing medications function in a similar way as the orally administered PDE5 inhibitors. Alprostadil is a vasodilator that is also a prostaglandin. Prostaglandins are naturally occurring fatty molecules in the body that have varying effects. Alprostadil, or prostaglandin E1, acts direction on vascular smooth muscle and the penile smooth muscle. It stimulates these cells to produce a molecule called cAMP which creates a chain reaction ultimately ending in smooth muscle relaxation and increased blood flow into the penis. Unlike the process targeted by PDE5 inhibitors, this process does not involve nitric oxide. Alprostadil can be taken in the form of a urethral suppository or pellet inserted into the urethral opening of the penis (MUSE), or as an injection into the spongy tissue on the side of the penis (Caverject, Caverject Impulse, Edex).

The doses and administration schedule of these medications vary with the type used, however, those who are self-injecting alprostadil should be monitored every several months by their provider. The most common side effects of aprostadil include:

• Pain in the penis, testes, or urethra
• Low blood pressure or high blood pressure
• Dizziness
• Injection site bleeding or bruising
• Headache

This is not an exhaustive list of all side effects of alprostadil. Your provider will help you determine what side effects you are at risk for. Men who have priapism (or prolonged erections), or any condition that could predispose priapism such as sickle cell anemia, multiple myeloma, or leukemia, should not take alprostadil. Individual’s on alprostadil should also be monitored for penile fibrosis, or the hardening of tissue in the penis. If fibrosis is suspected, treatment should be stopped immediately.^6-9