Chat transcript: One year after Viagra

(CNN) -- Dr. Myron Murdock is national medical director of the Impotence Institute of America. He spoke with CNN.com chat participants in March, one year after the impotence drug Viagra entered the U.S. market. Following is an edited transcript of that chat.

Dr. Murdock: Hello, all.

Chat Participant: What is the biggest impact you've seen in the medical community thus far since Viagra's approval?

Dr. Murdock: I think the No. 1 impact is that we now have a drug that works in a majority of patients, in about 80 percent of all patients, that is safe, that has really minimal side effects if the patients are properly selected, and that the average primary care medical doctor can give without using specialized medical services. When you sum it all up, this is the first simple drug for impotence that can be effectively given by any general medical doctor. The other thing is that this is really the first effective oral drug, and probably the beginning of many more oral drugs that will be developed for male and possibly female sexual dysfunction.

Chat Participant: Doctor, what got you into the area of a medicine for impotence?

Dr. Murdock: I have personally been doing male sexual dysfunction research since 1973, and I got into this area in 1973 when there was really the first effective form of treatment for erectile dysfunction, and that was penile implants. After that, we were trying to develop less invasive types of treatments, and from surgery came injection therapy, and from that came the insertion of prostaglandin pellets and, what we were all looking for, the ideal treatment, which was a drug which could be taken by mouth that was effective in resolving the majority of patients who have this problem with minimal side effects. It just so happened that Viagra was originally used in England to improve heart functions in patients who had severe heart disease and chronic chest pain, and it didn't work. But many of these patients, who were also impotent, were awakening in the morning with erections when they had been impotent One of the researchers at Pfizer Pharmaceuticals in England realized this and thought maybe it would work for impotence. That's how Viagra became a drug for impotence. I personally have been involved in the initial trials on Viagra dating back to about five years ago.

Chat Participant: Are you currently working on a drug for female impotence?

Dr. Murdock: Yes. In fact, in the last six months there have been trials in Europe on female sexual dysfunction using Viagra and the results of these trials will be coming out very shortly. There's also a drug called Vasomax, which is also going to be tried on female sexual dysfunction. And there is a prostaglandin pellet, which is going to be used also, and another drug also, called apomorphine. The interesting thing about female sexual dysfunction is that it has the same causes as male problems. It has a decrease in blood flow to the pelvic region. In the case of the male, it's not enough blood to the penis, and in the case of the female, it's not enough blood to the clitoris or vagina. So, all the drugs we are using for male dysfunction can be used for

Chat Participant: Why is Viagra able to be sold on the Internet? What's your opinion of drugs being sold over the Internet?

Dr. Murdock: I think that Viagra should probably not be sold on the Internet for several reasons. One, there is more to impotence, or sexual dysfunction, than just treatment. Impotence is a symptom of another problem. Most people who have a physical cause for their impotence have a disease entity that is causing the impotence, so you have patients out there with undiagnosed diabetes, vascular problems and heart disease whose first sign of a problem is impotence. In fact, one-third of all patients who present as impotence as their primary symptom of a blood vessel problem will end up with a serious complication within three years, either a heart attack or a stroke. So it is very important that these patients see a doctor, have a specific diagnosis made, and then be treated for that problem; otherwise they could end up with a life-threatening complication.

Two, even though we all recognize that Viagra is an extremely safe drug, contrary to what the media says, when given to patients on nitroglycerin or nitrates the combination can cause sudden death. There are approximately 125 drugs that contain nitrate, and many times patients don't even realize they are on a nitrate-containing drug. It takes a qualified physician to recognize this fact and ensure that his patient does not take the Viagra along with his nitrate-containing drug.

Three deals with patient follow-up. When a person goes on Viagra, he really needs to be seen by the physician in six to eight weeks, because the results of treatment may not be optimal, or the patient may be doing something that will minimize the effect of the drug. If it's sold on the Internet, then follow-up evaluation may be inadequate. An example is many times Viagra doesn't work because the patients are not waiting long enough, and you should wait one if not four hours for the drug to work. Another example would be that the patients are taking it on a full stomach, and the absorption of the drug is diminished with food. Another example would be if the patient takes the pill and doesn't realize that he needs sexual stimulation for it to work. A close friend called just a while ago and he hadn't realized that he needed sexual stimulation to make it work. If the patients are doing the right thing, there are ways of taking suboptimal responses and making them work. That's why you need a follow-up.

Chat Participant: What are the more common drugs that carry enough nitrates to cause a negative reaction when taken with Viagra?

Dr. Murdock: The more common drugs are ones used for heart disease, high blood pressure and angina. They include nitroglycerin patches that you apply to the skin like Nitro-Dur, long-acting nitroglycerin tablets like Imdur and sublingual pills that you put under your tongue. So any time you see a word like 'dur' you should be careful that it has nitrates in it. You really have to see a physician. But if you are taking medicine for heart, blood pressure or chest pain, you need to see your doctor. Hold on, and I'll refer to my list. Even I don't know them all without consulting this list. Here, I have it. A doctor should review the names of every drug, and if he doesn't know whether the drug does not contain nitroglycerin, he should look that drug up. There are so many drugs out there in various names, and in various companies, so make your doctor look it up.

Chat Participant: I have had patients taking Viagra who had very bad reactions and were not taking any of the known nitrate drugs. I believe the side effects are way underestimated.

Dr. Murdock: You can contact Pfizer. They can provide a complete list of all the drugs known that contain nitrates. Probably as many as 25 percent of the patients who take Viagra will have headaches, facial flushing, nasal congestion, stomach upset, and bright vision with blue-green halo effect. But in most of these cases, the response lasts less than 15-30 minutes, and it is a mild intensity. It is not severe enough to make patients stop taking their Viagra. After they take it three or four times, these effects go away. There's less than 3 percent of all patients who will get these side effects so severe that they will stop taking the drug.

Chat Participant: My two patients who took Viagra experienced increased urination and unprovoked nosebleeds; in the other patient, painful urination.

Dr. Murdock: I have never heard of painful urination as a complication of Viagra, but it's possible it may have been related to some kind of prostatic problem, which is not uncommon with sex, or he was trying to void while he had an erection and had pain. As far as the nosebleeds are concerned, we do know that Viagra increases the blood flow to the nasal passages, and nosebleeds are a common side effect. I'd love to discuss further. CNN folks indicate they'll forward your contact information to me if you'll give it to them.

Chat Participant: Can testosterone patches serve as an alternative to Viagra?

Dr. Murdock: The answer is no. About 2-16 percent of patients who have erectile dysfunction will have male hormone deficiency. Those patients should be treated unless there is some other problem, like prostate cancer. They should be treated with hormone therapy either with patches or by injection, a daily patch, or injection every two weeks. Only 50 percent will produce normal erectile function. The other 50 percent have more than just the hormonal problem, and it's that 50 percent that will probably respond to Viagra. However, the response will be much better if they are treated for their hormone deficiency. In addition, the hormone deficiency when treated will significantly improve desire in these men, whereas Viagra has no effect whatsoever on desire. It only has an effect on erectile dysfunction.

Chat Participant: What do you think about herbal supplements that claim they can treat impotence without having to get a prescription?

Dr. Murdock: I think the answer is really simple. Viagra is such a phenomenal drug working so well with minimal side effects, and there are no herbal supplements that have anywhere near the success rate as Viagra and may in fact have many more side effects. Remember that these have not been studied and are not FDA-approved, so the side effects are not known. Viagra has been more studied than any drug in the FDA.

Chat Participant: Why has it been the most studied drug?

Dr. Murdock: The basic concepts that led to Viagra ended up winning the Nobel Prize for three scientists. So the group of drugs that Viagra belongs to is a very important group of drugs that, in the future, are going to be used for treatment of other diseases such as cancer, immune deficiency, and possibly even cardiac diseases. So, since this was the first drug of its type to be used in large quantities by people throughout the world, the FDA wanted to be very sure that the drug was extremely safe, especially in combination with other drugs. I think Pfizer, who developed this, wanted to be sure they had a safe drug. In fact, more people have taken Viagra than any drug ever manufactured.

Chat Participant: Should Viagra be used only as a last resort?

Dr. Murdock: The answer is no. It should be used as the first resort. Everybody who has male sexual dysfunction who is not on a nitrate should use Viagra as their first line of drug and push the dosage to 100 milligrams before deciding the drug is not effective. Viagra is now the main treatment for male sexual dysfunction and should be tried by all, either alone, or in combination with other drugs, such as Muse, which is a prostaglandin pellet. Extensive studies have been done with Viagra and nearly all other classes of medications, including high blood pressure medications and heart medications, and there have been no significant interactions. There have been animal laboratory studies showing that dogs treated with Viagra actually live longer than dogs that aren't treated with Viagra. There is also lower incidence of heart and coronary disease in these dogs as well when they are treated with Viagra. If you look at the original 160 Viagra deaths, almost all these patients were patients who were on nitrates unknowingly or had such severe heart disease that they shouldn't have been having sex. The reality is that of the first 3,000,000 people taking Viagra in the first three months was 160. Under normal circumstances, the normal death rate was 1,250 per million, which statistically shows that Viagra actually decreased the death rate in that population.

Chat Participant: Dr. Murdock, do you see or foresee the price of Viagra coming down now with such wide usage?

Dr. Murdock: The retail price is $10 per pill, but many pharmacies are selling at $7.50, close to their cost. I think in time the price will drop, as more oral drugs hit the market as effective as Viagra for male and female dysfunction. It turns out that this particular drug is not an easy drug to manufacture. When you think about the cost of this one pill, there are many other pills that sell for $5 to $10 where the cost of manufacturing is less. So $10 is not all that expensive in the modern pharmaceutical industry, but I do think it will come down.

Chat Participant: What is the relationship/importance between psychological and physiological dysfunction?

Dr. Murdock: Sexual problems are predominantly physical, with about 85 percent vs. 15 percent for psychological. Viagra works in almost 100 percent of the patients who have a psychological cause. In time, the patient may no longer need the Viagra because performance anxiety is relieved, and once that disappears, he's fine. In the case of physical impotence, Viagra works in approximately 75-80 percent. It's important to know it's physical because the cause may be treatable in and of itself, for example diabetes or male hormone deficiency. In addition, by making a diagnosis of the cause, one may prevent future catastrophic results. For instance, a patient with underlying heart disease and decreased blood flow to the penis. He presents to the doctor with impotence, but his real problem is hardening of the arteries, and if he's not diagnosed to have coronary heart disease, he has a good chance of having a heart attack within three to five years.

Chat Participant: Do you have a favorite joke about Viagra?

Dr. Murdock: I hear so many of them I stopped remembering them. But the one I like the most is, "What do you get when you rub Viagra into your scalp?" The answer is "Don King."

Chat Participant: Thanks, Dr. Murdock! Visit our chat calendar for a complete list of future events and past chat transcripts.