If you have erectile dysfunction, you don’t have to shop for the increasingly rare rhinoceros horn or the often deadly Spanish fly, which is made from the remains of the blister beetle. There are hundreds of other reputed aphrodisiacs, but none have been found to work.

What about Viagra, Levitra, and Cialis?
You don’t even have to inject a drug into your penis, which was the best thing that Western medicine had to offer just eight years ago. Before that, the best you could do was either use a pump to draw blood into your penis or a penile implant, which meant the surgical placement of plastic rods in your penis.

Ouch!

Now, we have a choice of three quite effective and well tested oral drugs for erectile dysfunction (often described by the acronym ED). They are not aphrodisiacs, because they will not increase sexual drive. They work by blocking an enzyme called phosphodiesterase-5, or PDE-5. This helps the smooth muscles in the penis to relax, which effectively increases blood flow, allowing an erection. But for them to be effective, sexual stimulation is also required.

ED is the consistent or recurrent inability of a man to attain and/or maintain a penile erection sufficient for sexual performance. Obviously an intensely private matter, it is not something that we have begun to talk about in public until quite recently. Consequently it is a common health condition among men that is largely untreated. And it has only since Viagra (sildenafil citrate) came on the market in April 1998 that we have begun to realize how many men suffer from ED.

The best estimates are that some degree of ED affects more than one half of all men over the age of 40—perhaps 152 million men worldwide and 30 million men in the United States alone. Despite this high prevalence, nine out of 10 men in the U.S. have not yet sought treatment from a physician.

ED is three times more prevalent among men who have diabetes than in the general population. More than half of men with diabetes notice the onset of ED within 10 years of their diagnosis. It occurs in nine percent of men with diabetes between age 20 and 29 years and rises to 95 percent by age 70.

Surprisingly, ED is more common among men with type 2 diabetes than among those with type 1, according to Martyn A. Vickers, MD, Chief of Surgery, Togus (Maine) VA Medical Center, and Associate Professor of Urology, University of Massachusetts Medical Center. He writes in “Phosphodiesterase type 5 inhibitors for the treatment of erectile dysfunction in patients with diabetes mellitus,” International Journal of Impotence Research (2002) 14, 466-471; abstract online at PubMed. Some 46 percent of men with type 2 diabetes have ED. This compares with 32 percent of those with type 1 diabetes.

So add ED to your list of common complications of diabetes. ED is often a manifestation of neuropathy. Like peripheral neuropathy, to which ED is often related, there is no “one size fits all” treatment. But unlike peripheral neuropathy, we now have in our arsenal three drugs that are effective for most men.

These three drugs are closely related:

• Viagra Most well known and available in the U.S. for the past five years is Viagra (sildenafil citrate), which Pfizer Inc. produces. The product’s official website is http://www.viagra.com. The biggest difference among these drugs is how long they last. “Take Viagra about one hour before you plan to have sex,” the Viagra website http://www.viagra.com/consumer/general/importantInfo.asp says. “Beginning in about 30 minutes and for up to 4 hours, Viagra can help you get an erection if you are sexually excited.”
• Levitra, pronounced Luh-VEE-trah, (vardenafil HCl), obtained FDA approval in August 2003 and became available in the U.S. later that month. Bayer AG and GlaxoSmithKline plc co-developed and co-promote it. The product’s official website is http://www.levitra.com. “Maximum observed plasma concentrations after a single 20 mg dose in healthy volunteers are usually reached between 30 minutes and 2 hours (median 60 minutes after oral dosing),” according to the product’s official website at http://www.univgraph.com/bayer/inserts/levitra.pdf.
• Cialis, pronounced see-AL-iss, (tadalafil), obtained FDA approval in November 2003 and became available in December. In February 2003 it was launched in Europe. Eli Lilly and Company, partnering with the drug’s original developer, ICOS, market it in a joint development venture. The product’s website is http://www.cialis.com/index.jsp. In Europe this drug already has a catchy nickname. It’s known there as “le weekend” pill. The product’s label says that Cialis can improve erectile function for up to 36 hours.

This is the only drug where I was able to find a curve of its effectiveness. Source of graphic: http://www.univgraph.com/bayer/inserts/levitra.pdf

Aside from how long these three drugs work, they are chemically similar and have similar side effects. Apparently, the biggest difference is that men using Viagra are more likely to experience temporary abnormalities of color vision. Additionally, taking Viagra with food decreases its effectiveness by 29 percent, while food has little if any effect on Levitra or Cialis.

They are even priced close to each other. Price is an important consideration, especially if your health insurance plan doesn’t include these drugs in its formulary.

The best legitimate prices I have been able to find come from Drugstore.com. This online pharmacy lists 10 Viagra tablets of 100 mg each at $87.99. Strangely, the 25 mg and 50 mg tablets list for the same price.

Likewise, Drugstore.com lists 10 Levitra tablets of 20 mg each at $87.99. The 2.5 mg, 5 mg, and 10 mg tablets list for the same price. The Drugstore.com price for 10 Cialis tablets of 5 mg, 10 mg, or 20 mg each is nearly the same—$89.99.

Spam offering Viagra, Levitra, and/or Cialis is rampant. But another strange pricing situation is that the prices at which spammers offer these drugs are far higher.

None of these drugs is inexpensive. Generic versions of prescription drugs are generally much less expensive, so you might be tempted to buy a generic version of Viagra, Levitra, or Cialis.

That could be a serious mistake. All generic versions of these drugs are manufactured abroad—often in third-world countries—and none of them have FDA approval.

A fourth new drug for ED, Uprima (apomorphine HCl), works on the brain and nervous system to trigger an erection. An FDA advisory committee is concerned about its safety, and it is not for sale in the United States. It is, however, marketed in Europe and Latin America. Uprima was developed and marketed by TAP Pharmaceutical Products Inc., a joint venture between Abbott Laboratories and Takeda Chemical Industries Ltd.

The company’s website is http://www.tap.com.

Which one of these drugs is right for you? That’s a question that you are going to have to answer yourself.

Dr. Vickers, whose study I link above, attempted to compare Viagra, Levitra, and Cialis on the basis of their Phase 3 trials of efficacy and safety for the general population and specifically for men with diabetes. However, criteria for inclusion, exclusion, classification of ED, dosing methodology, and duration of the studies varied too much to make valid comparisons possible.

Eventually, some researcher might publish head-to-head comparative trials of these drugs. Meanwhile, any of them look like they are better than the alternative.

Update
Tim Cady reminds me that the pump—which is painless—works in many cases where these new drugs are ineffective.
Most insurance plans and medicare provide coverage.