Erectile dysfunction (ED) is when a man has problems either getting or sustaining an erection. According to the National Institutes of Health, approximately 18 million men suffer from ED at some time in their life. It is more common in men who are older, with over 70 percent of men over 70 years old having ED and only 5 percent of men between the ages of 20 to 39 having problems with erections. 
In the past, ED was considered a psychological problem. Men who had trouble getting or sustaining an erection were thought to have performance anxiety, relationship issues or guilt over indiscretions. But in recent years, more is understood about ED and research has shown that the majority of men with ED have some underlying physical condition, such as diabetes, obesity, kidney disease or prostate cancer, causing the problems.
In addition to medical conditions, over-the-counter, prescription and illegal drugs can also contribute to ED. If you, or your partner, are having trouble reaching or sustaining an erection, you may want to check any medications you are taking to find out if these may be contributing to your ED. While it is important to talk with your doctor about possible side effects of any medication you are prescribed and discuss ways to minimize these, the following list gives an overview of some of the types of medications which may create or contribute to sexual problems.
- High blood pressure medications
- Parkinson's disease medications
- Hormonal medications
- Anti-inflammatory medications
- Muscle relaxers
- Anti-seizure medications
- H2 blockers
Many of these medications may be needed to treat a serious medical condition. If you are taking one of these and experiencing ED, you should not just stop taking it. Some of these medications will cause serious withdrawal if suddenly stopped. You should always speak with your doctor before discontinuing any medication. Your doctor may be able to suggest a different medication which has no or minimal sexual side effects or be able to provide options for combating this side effect.
Some of these medications can be found in over-the-counter formulas, such as anti-inflammatory medications (ibuprofen) or H2 blockers (Tagament, Zantac, Pepcid). It is important to let your doctor know all medications you are taking, including over-the-counter, supplements and vitamins. This information can help you work together with your doctor to determine the cause of your ED.
Besides medications taken for a medical condition, there are a number of recreational drugs which can contribute to ED:
These drugs can affect the central nervous system and, in some cases cause damage to your blood vessels - which may cause permanent ED. Although many of the problems associated with these drugs are well known, it is not always understood that one of the effects can be sexual problems.
For more information see Health Central's ED Community
"Drugs That May Cause Impotence," Updated 2010, Oct 11, Updated by David Zieve, M.D., A.D.A.M. Medical Encylclopedia
 "Kidney and Urologic Diseases Statistics for the United States," Updated 2012, Feb 15, Staff Writer, National Institutes of Health
"Medications That May Cause Erectile Dysfunction," Date Unknown, Staff Writer, Cleveland Clinic