Questions and Getting Help for ED
How Do ED Drugs Work?
Medically reviewed by Dr. Larry Lipshultz M.D
If you are experiencing erectile dysfunction, you might be considering taking medication and are wondering, how do ED drugs work? If you want to try an oral treatment that produces good results, then you have five options available. All five FDA-approved drugs for erectile dysfunction—Cialis (tadalafil), Levitra (vardenafil), Staxyn (vardenafil), Stendra (avanafil), and Viagra (sildenafil)—work in a similar way, with some slight variations in how long they take to be effective, how long the effect lasts, and side effects. Generally, if you try one of the five drugs and you don’t have success, chances are the other four will give you the same result.
Although a great number of men experience erectile dysfunction–10 percent of men around the world, including 30 million in the United States—many do not know exactly what erectile dysfunction is nor how the most popular treatments for them in the world operate. Here are the facts.
How Does An Erection Occur?
Many chemical interactions occur between the time a man begins to get sexually aroused and when he achieves an erection. Before you can understand how ED drugs work, it is important to know the sequence of these interactions, the chemicals involved, and how they work together.
Basically, when arousal occurs the brain sends a signal to the penis along nerve fibers. Nerve cells in the corpora cavernosa, two spongy tubes in the penis, begin to produce nitric oxide, which stimulates an enzyme called guanylate cyclase. This enzyme transforms a chemical called GTP into yet another chemical called cyclic guanosine monophosphate (cGMP). The cGMP causes smooth muscle in the arteries to relax, which allows blood flow to the penis to increase. The veins that carry the blood away close up, or constrict, which traps the pressurized blood in the corpora cavernosa. The result is an erection.
Part of this sequence involves yet another chemical called PDE (phosphodiesterase), which breaks down cGMP and turns it back into GTP. When the supply of cGMP is interrupted, an erection cannot occur.
One of the most common reasons a man develops erectile dysfunction is that the arteries in the penis do not dilate enough when they receive the signals. Although nitric oxide is produced, there is not enough cGMP to maintain an erection. Men who have this situation need something that increases blood flow to the penis, and that is what the four ED drugs can do.
How Do ED Drugs Work?
Erectile dysfunction drugs (known as phosphodiesterase inhibitors or PDE5s) work by inhibiting PDE5, the specific kind of PDE that is found mainly in the penis. When a man takes an erectile dysfunction drug, it enters the bloodstream and targets the PDE5 enzyme in the penis.
Once the drug attaches to the PDE5 enzyme, it disables most of it, which means it can no longer break down cGMP. This allows cGMP to accumulate in the penis: the more cGMP a man has, the greater the blood flow, and thus the better the erection.
Depending on which drug you take, it stays in the body for several hours to more than a day before it is eliminated by the liver and kidneys. While the drug is still in the bloodstream, you can engage in sexual activity and (hopefully) achieve and maintain an erection.
Are All Oral Erectile Dysfunction Drugs Alike?
Yes and no. Although they all work in a similar way, they differ in how long and how fast the medication works. For example:
Levitra and Viagra take effect in about 30 minutes, but Levitra can be effective for about 5 hours while Viagra lasts about 4 hours
Cialis and Stendra can both spring you into action within about 15 minutes, but Stendra lasts only up to 12 hours while Cialis can be effective for up to 36 hours
Staxyn is an orally disintegrating form of Levitra (but is not interchangeable with it) and can be effective in less than 30 minutes
Thus far, Cialis is the only oral erectile dysfunction drug that is also approved by the FDA to treat benign prostatic hyperplasia, which is an added benefit for men who are experiencing symptoms of this prostate condition