Viagra: Limited success among diabetic men

Be careful of prescribing for sedentary patients

Viagra has proven a wildly popular success by restoring sexual function to millions of men who suffered from a variety of dysfunctions for a variety of reasons. Since 60% of diabetic men suffer from erectile dysfunction caused by their disease, many hoped Pfizer Pharmaceuticals’ wonder drug would be a magic pill to restore them to normal sex lives.

Not always the right choice

However, the reality is somewhat less glamorous, and there are serious caveats for a practitioner considering prescribing Viagra for a diabetic patient. Some specialists say other methods are probably safer and certainly more reliable.

While Pfizer’s clinical trials including 3,500 men, 16% of them diabetic, showed a 59% success rate for diabetics using Viagra, some specialists report a significantly lower rate of success and others say the drug is very effective. (See box, p. 87.)

J. Francois Eid, MD, associate professor of urology at Weill Medical College of Cornell University in New York City and director of the Male Sexual Function Center of New York Presbyterian Hospital, also in New York City, says 55 % of his patients have achieved success with Viagra.

And his colleague at Columbia Presbyterian Medical Center in New York City, Gerald Hoke, MD, MPH, a urologist specializing in erectile dysfunction, says Viagra works for about half of his diabetic patients. (See chart, below.)

Success of Viagra
Clinical trials of 4,000 men Success rate
Patients with spinal cord injuries 83%
Non-diabetics 68%
Diabetics 55%
Patients with prostatectomies as a result of cancer 40%
Source: J. Francois Eid, MD, Weill Medical College of Cornell University, New York City. 

Different physical characteristics

Eid, who participated in the Phase 3 Viagra trials and began prescribing the drug to non-insulin-dependent diabetes mellitus and insulin-dependent diabetes mellitus patients in 1995, notes a particular pathology of the penis among diabetic men.

"While in non-diabetics, the main arteries feed blood to the penis to cause an erection, in diabetics, the small arteries are obstructed," Eid says. These men have scarring, shrinkage, deformities, or plaques in the penis known as Peyronie's disease with a characteristic abnormal penile curvature." Because the disease is degenerative and the characteristics are not seen in other types of erectile dysfunction, Viagra is less than the wild success patients had hoped for, Eid says.

With 123 reported deaths, 69 of those directly attributed to Viagra, specialists warn against prescribing Viagra for diabetic men without a thorough investigation.

"Obviously you can’t give it to anybody taking nitrates, and a lot of our patients have heart diseases and are taking nitrates, so they just can’t use it," says Kathryn Tuck, MD, associate director for clinical trials at Naomi Berrie Diabetes Center at Columbia Presbyterian Medical Center and assistant professor of medicine at Columbia University.

Tuck, an endocrinologist who reports a high success rate among her patients at the newly opened Naomi Berrie Diabetes Center, says, "The other big worry is that there have been some deaths reported in men who have used Viagra and weren’t taking nitrates, but presumably had heart disease. Since we always think that diabetic men could have heart disease but are asymptomatic, we need to be careful."

All three specialists agree that stress tests should be administered to any diabetic patient at risk for complications before a prescription for Viagra is dispensed.

Tuck is particularly leery of prescribing the drug for sedentary patients. "If they haven’t been exercising much and they have risk factors for heart disease, I would probably give them an exercise test before I gave them Viagra to make sure they don’t have any heart disease."

Eid concurs, "Primary care physicians know which patients are couch potatoes. Since they experience an increase in oxygen demands during sex, if a patient is totally sedentary or has a history of myocardial infarction, that raises a red flag."

He notes that a sexual encounter will increase the heart rate to 120 to 130 and that with Viagra, there is a delayed ejaculation, so the man will be thrusting for a longer period of time.

Hoke says one-third of all men who resume intercourse have signs of ischemia and about 7% of them actually develop clinical signs of chest pain up to 24 hours after intercourse. "We had a discussion as to whether or not you need to do an extensive workup [before prescribing Viagra for diabetic men]," Hoke says. "I don’t know if you do or don’t, but clearly you have to be very cautious in diabetic men who also have other signs of coronary heart disease, especially if they haven’t had intercourse for quite a while."

"You really need to use your common sense," he continues. "If the guy says, Well, I jog three miles a day,’ you probably don’t need to do a stress test. But if the guy’s a little overweight and hasn’t had sex in two years, and maybe smokes, then you probably should do one."

Other complications are comparatively minor and appear to be temporary.

Tuck says she had one patient who "started having some chest pain, so he got nervous and stopped using it."

Hoke says he had one diabetic patient who had visual disturbances slightly different than those described by the manufacturer, and his lasted a bit longer. "His visual field became dark as opposed to the blue haze that has been described, and he said it lasted until the next morning," Hoke says. "It turns out that this particular guy probably has some retinopathy."

Retinopathy is not yet a disqualifier for the drug, but Hoke says it needs to be watched. "I think if we see this type of complication coming out, it probably will [become a contraindication]. I don’t think we really understand fully the reason why we have visual disturbances."

Some refuse to take Viagra

Many diabetic men are so fearful of the possible complications of Viagra that they refuse prescriptions. Eid notes that many of his patients on penile injections who were candidates for Viagra declined prescriptions for sildenafil because they were worried about possible heart problems "even though there was no clinical reason why they should not have a good result." Also, he says, many patients were happy with the predictability of erection achieved through penile injections and did not want to experiment with a new product.

Physicians should counsel patients about the use of Viagra, the experts say, to be sure patients understand that the drug is not an aphrodisiac but requires considerable sexual stimulation to be effective.

Eid says Viagra is only a small part of his arsenal against diabetes-induced impotence. He is highly enthusiastic about Caverject (alprostadil) because of its high success rate, about 85%, its low cost (about half the $7.50 to $10 cost per pill) of Viagra, and the fact that Medicaid, Medicare, and some managed care organizations will pay for it.

He says diabetic men are not usually as squeamish about needles as their non-diabetic peers "and with the neuropathy most diabetic men have, they do not even feel the injection of a fine needle at the base of the penis."

He is also enthusiastic about the penile prosthesis because of its almost unfailing success rate (99%). "It’s very discreet. For some men, their wives don’t even known they have a prosthesis," Eid says. "The penile prosthesis is the most successful procedure in the whole field of urology, even more so than the treatment of kidney stones, which is only 85% effective."

Eid concludes that he is puzzled that so many men, diabetics in particular, fail to seek treatment for erectile dysfunction when many effective solutions are available.

For more information, contact:

J. Francois Eid, MD, Associate Professor of Urology, Weill Medical College of Cornell University, New York City. Telephone: (212) 746-5473.

Gerald Hoke, MD, Urologist, Columbia Presbyterian Medical Center, New York City. Telephone: (212) 305-5524.

Kathryn Tuck, MD,Associate Director for Clinical Trials, Naomi Berrie Diabetes Center at Columbia Presbyterian Medical Center and Assistant Professor of Medicine, Columbia University Naomi Berrie Diabetes Center, New York City. Telephone: (212) 304-5494.