Phosphodiesterase-5 inhibitors (PDE-5 inhibitors) for erection problems

Examples

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Brand Name	Chemical Name
Viagra	sildenafil citrate

Brand Name	Chemical Name
Cialis	tadalafil

Brand Name	Chemical Name
Levitra	vardenafil

Phosphodiesterase-5 inhibitors (PDE-5 inhibitors) are taken at least an hour before you plan to be sexually active. PDE-5 inhibitors will result in an erection only if you are sexually stimulated.

How It Works

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During an erection, blood fills tissue in the penis, causing it to enlarge and become stiff. The PDE-5 inhibitors relax smooth muscle, allowing the penis to fill with blood.

Why It Is Used

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PDE-5 inhibitors can be used when an erection problem (erectile dysfunction) is caused by:

• Diabetes.
• High blood pressure.
• Spinal cord injury or other problems affecting nerve function.
• Prostate surgery.
• Side effects of medications.
• Emotional or psychological causes.

How Well It Works

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PDE-5 inhibitors are effective treatment for erection problems. A review of trials has shown that 83% of men with erection problems who used Viagra had improved erections that allowed them to have intercourse.¹ Initial studies show Levitra and Cialis have rates of success similar to those of Viagra.² Viagra has been studied extensively and used by millions of men; its side effects and long-term effects are well recognized. Levitra and Cialis are new drugs in which long-term effects have not been studied.

PDE-5 inhibitors should be taken at least an hour before you plan to be sexually active.

One study found that Cialis, called "the weekend pill," enhanced the ability to have erections for 24 to 36 hours after taking it.³ Viagra and Levitra usually enable a man to get an erection at any time for 4 or more hours after taking it.

Viagra does not work as well as it would otherwise if you eat a high-fat meal around the time you take it, so many doctors recommend you take it on an empty stomach. Levitra may be slightly less effective if you eat a high-fat meal, but a moderate-fat meal does not reduce its effectiveness; Cialis works without regard to what you eat.⁴

Side Effects

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Do not take PDE-5 inhibitors if you are taking any medication that contains nitrates, such as nitroglycerin. This combination can lower blood pressure dangerously, possibly leading to a stroke, a heart attack, or death. If you are taking a medication called an alpha-blocker—used to treat high blood pressure or an enlarged prostate—check with your health professional before you take a PDE-5 medication.

Other side effects are fairly uncommon when taking PDE-5 inhibitors. They include:

• Headache.
• Skin flushing.
• Indigestion.
• Nasal congestion.

A few men find that PDE-5 inhibitors affect their vision for a few hours after taking it, usually by causing a slight bluish tinge to their vision. A few men become more sensitive to light. These effects go away in a few hours.

Viagra, Cialis, and Levitra may be linked to a rare type of vision loss. If you experience sudden vision loss or vision-related problems while taking these drugs, the U.S. Food and Drug Administration (FDA) advises you to talk to your doctor and seek medical care immediately.

See Drug Reference for a full list of side effects. (Drug Reference is not available in all systems.)

What To Think About

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Health experts have debated the use of PDE-5 inhibitors in men with heart disease, because deaths have been reported in men who used Viagra. The 1999 American College of Cardiology/American Heart Association (ACC/AHA) Expert Consensus Document noted that PDE-5 inhibitors may be dangerous for people who:⁵

• Have coronary artery disease (CAD).
• Have heart failure and low blood pressure.
• Are taking many different drugs for high blood pressure.

However, several studies have reported that some men with heart problems may be able to take PDE-5 inhibitors safely.

• One study found no evidence of increased risk of heart attack or CAD in men who use Viagra.⁶
• Another study in men with CAD reported that Viagra does not lead to heart attack and that heart attacks and other cardiovascular problems reported after taking Viagra may be related more to the physical activity of intercourse than to the medication.⁷
• A study of 35 men found that Viagra is safe for men with moderate heart failure.⁸

Sexual activity is exercise. If you have a heart condition and have not been sexually active for a while, talk with your health professional to make sure you can safely engage in sexual activity.

PDE-5 inhibitors are not prescribed for anyone who may take nitroglycerin in an emergency.

Tell your health professional if you are using PDE-5 inhibitors and are going to have a test for heart disease (such as a stress treadmill test, cardiac catheterization, stress thallium, or stress echocardiography). You should avoid taking PDE-5 inhibitors for 24 to 48 hours before such a test.

When considering PDE-5 inhibitors for erection problems, it is important to include your partner in your discussions.

If you take any medications, discuss PDE-5 inhibitors with your health professional before using them.

PDE-5 inhibitors can be prescribed by any doctor. You do not have to see a doctor who specializes in sexual health. PDE-5 inhibitors are also available on the Internet; if you obtain the medication through this route, you should discuss its use with your doctor.

Viagra costs $8 to $10 per pill, and not all insurance plans will cover the cost of the medication. Most insurance plans that do cover Viagra will approve only a limited supply.

Complete the new medication information form (PDF) (What is a PDF document?) to help you understand this medication.

References

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Citations

1. Webber R (2005). Erectile dysfunction. Clinical Evidence (13): 1120–1127.

2. Gresser U, Gleiter CH (2002). Erectile dysfunction: Comparison of efficacy and side effects of the PDE-5 inhibitors sildenafil, vardenafil, and tadalafil. European Journal of Medical Research, 7(10): 435–446.

3. Porst H, et al. (2003). Efficacy of tadalafil for the treatment of erectile dysfunction at 24 and 36 hours after dosing: A randomized controlled trial. Urology, 62(1): 121–125.

4. Seftel AD, et al. (2004). Erectile dysfunction: Etiology, evaluation, and treatment options. Medical Clinics of North America, 88(2): 387–416.

5. Cheitlin MD, et al. (1999). Use of sildenafil (Viagra) in patients with cardiovascular disease. ACC/AHA expert consensus document. Circulation, 99(1): 168–177.

6. Shakir SAW, et al. (2001). Cardiovascular events in users of sildenafil: Results from first phase of prescription monitoring in England. BMJ, 322(7287): 651–652.

7. Arruda-Olson AM, et al. (2002). Cardiovascular effects of sildenafil during exercise in men with known or probable coronary artery disease. JAMA, 287(6): 719–725.

8. Webster LJ, et al. (2004). Use of sildenafil for safe improvement of erectile function and quality of life in men with New York Heart Association classes II and III congestive heart failure. Archives of Internal Medicine, 164(5): 514–520.

Credits

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Author	Ralph Poore
Editor	Kathleen M. Ariss, MS
Associate Editor	Pat Truman
Associate Editor	Terrina Vail
Primary Medical Reviewer	Adam Husney, MD - Family Medicine
Primary Medical Reviewer	E. Gregory Thompson, MD - Internal Medicine
Specialist Medical Reviewer	Christopher G. Wood, MD, FACS - Urology/Oncology
Last Updated	June 13, 2006