Posts Tagged ‘sildenafil’

Move over Viagra

// November 15th, 2010 // No Comments » // Impotence

Ever since sildenafil (Viagra, Pfizer) hit the market in 1998 as the first oral medication for erectile dysfunction (ED), people have been wondering, “What’s next?”

New data presented at a recent meeting of the European Association of Urology demonstrated strong results for two potential new treatments. Bayer AG presented promising data for its investigational phosphodiesterase (PDES) inhibitor, vardenafil, now in phase III studies. In an analysis of 580 patients, vardenafil improved erections in up to 80% of men, as well as increasing the ability to complete sexual intercourse with ejaculation.

In a separate study, vardenafil was found to be highly selective at targeting the PDE5 enzyme. PDE5 selectivity is of potential clinical importance because phosphodiesterases are widely distributed throughout the body, with PDE3, for example, playing an important role in cardiac contractility.

Lilly/ICOS unveiled compelling results for its next-generation PDE5 inhibitor, IC351 (Cialis). In a placebo-controlled phase III study in men with difficult-to-treat diabetes-related ED, up to 64% of men reported improved erections, compared with 25% for placebo.

In preclinical investigations, Cialis demonstrated an even higher affinity for the PDE enzyme than sildenafil did. Researchers saw no significant changes in clinical laboratory values, ECGs, or blood pressure in the phase III trial.


// October 27th, 2010 // No Comments » // Impotence

Once men with preexisting heart problems and those using nitrate medications are excluded, there remain millions of impotent men for whom Viagra treatment is both useful and appropriate. Those men should know how to use Viagra to achieve maximum benefit.

The usual starting dose of Viagra is 50 mg, taken one hour before planned sexual activity.
Men over age sixty-five are advised to start with a 25-mg dose, again one hour before planned sexual activity.
Men who have no adverse effects from taking one dose of Viagra but do not achieve an ideal erectile response at that dose may take the next-higher dose, up to a total single dose of 100 mg.

Men who have side effects such as light-headedness, dizziness, or headache at any dose are encouraged to “step down” and try a lower dose to minimize or eliminate these adverse effects. Some men who are able to tolerate the 50-mg dose but feel they have not had a fully satisfactory dose may do better on the higher 100-mg dose of sildenafil.


// October 25th, 2010 // No Comments » // Impotence

A man’s firm and turgid erection persists until he achieves climax and ejaculates. After ejaculation, his erection fades and his penis returns to its limp (flaccid) state. That process, the conversion of the penis from the sexually prepared and erect condition back to its normal resting flaccid state is also under chemical control. Another intrapenile chemical, an enzyme, called phosphodiesterase 5 (PDE-5) determines whether an erection will stand or collapse.

Enzymes work to either activate or inactivate proteins, and in this case, what is inactivated by PDE-5 is cGMP, the chemical that helped the penis remain erect. As levels of intrapenile cyclic GMP levels fall, so does a man’s erection.

Sildenafil (Viagra) inhibits PDE-5 and allows a man’s cGMP levels to remain elevated. When cGMP levels remain high, a man’s erection persists.

This is good news for men who suffer from impotence or erectile dysfunction.

As long as Viagra helps maintain high intrapenile cGMP levels, a man’s erectile vigor is sustained. With Viagra treatment, between 65 percent and 80 percent of impotent men are able to acquire and maintain erections satisfactory for sexual intercourse.

Male Sexual Chemistry
Body Chemical Does What?
Nitric Oxide Synthase (NOS) Releases Nitric Oxide (NO)
Nitric Oxide Starts blood flowing into penis causing
swelling (tumescence)
Cyclic GMP (cGMP) Increases blood flow so that penis
becomes firm and rigid
Phophodiesterase 5 (PDE-5) Metabolizes cGMP causing loss of erection
Sildenafil (Viagra) Inhibits PDE-5 allowing cGMP levels and
a man’s erection to be sustained


// October 25th, 2010 // No Comments » // Impotence

The development of a “potency pill” that is a medication that could actually make it easier for men to have sex was sheer fantasy until scientists stumbled on sildenafil (Viagra). Originally called UK-92480, then given the generic name sildenafil and more recently the brand name Viagra, this new medication was widely heralded as the pill that could cure impotence.

Sildenafil (Viagra) was originally developed as a blood-pressure-lowering (antihypertensive) medication. Early studies designed to evaluate exactly how effectively sildenafil lowered blood pressure revealed remarkable and unexpected side effects. 1 Hypertensive men taking sildenafil started to experience a surprising number of frequent firm erections.


Viagra, unlike yohimbine, does not purport to be an aphrodisiac, something that can mysteriously heighten a man’s sexual desire. Rather, Viagra has been specifically designed to improve the vigor of a man’s erection. It does this by bolstering a man’s own natural sexual chemistry to make it easier for his penis to acquire and maintain a firm erection during sex.

To date, we know the following about this medication. Viagra speeds up the rate at which blood flows into the penile erectile bodies, the corpora cavernosae. To understand exactly how Viagra works, you have to know a little about what is rapidly emerging as the new science of male sexual chemistry.


The names of the chemicals involved in male sexual chemistry are not particularly erotic, but they are the driving force of men’s sexuality. The interaction of these chemicals is not really that complicated once you know the names of the players.

1. NOS stands for nitric oxide synthase, the enzyme that releases NO (nitric oxide) into the penis.
2. NO starts blood flowing into the penile erectile chambers to start penile swelling, or tumescence.
3. cGMP (short for cyclic GMP) accelerates penile blood flow, resulting in penile rigidity.
4. PDE-5 (phosphodiesterase-5) inactivates cGMP, causing both cGMP levels and a man’s erection to dwindle.
5. Sildenafil (Viagra) blocks PDE-5 and helps maintain cGMP stability as well as the vigor of a man’s erection

Here’s how it all works.

During sexual excitement, a man’s own natural body chemicals diffuse or are transmitted into his penis to trigger the release of nitric oxide (NO). Blood starts to flow into the penile erectile chambers so that the penis plumps up. This is known as tumescence. But the penis is still not ready for sex. The swollen or tumescent penis must be taken to the next plateau, penile rigidity.

Penile rigidity requires a second locally generated chemical called cyclic GMP (cGMP). It is the presence of cGMP that maintains the furious onrush of blood needed for a man’s penis to be converted from tumescent to rigid.

As cGMP takes center stage and even more blood flows into the penis, the pent-up pressure caused by accelerated penile blood flow is so intense that the penis looks like a stuffed sausage straining at its casing. As blood pressure within the penis mounts, the tiny draining emissary veins are choked off so that no blood can leave the penis.

A man’s sexual capability is therefore dependent on a chemical chain reaction beginning with the enzyme NOS, followed by NO, and finally culminating in cGMP to activate the blood flow needed for him to get an erection. The system can break down at any point.

Men who have a substandard quotient of the enzyme NOS within their penile tissue cannot make enough NO to initiate the full and unfettered flow of blood into the penile erectile chambers and as a consequence have difficulty developing a full erection. Lower than normal NOS levels are found in men who are heavy cigarette smokers and in those who have diabetes mellitus or low testosterone levels. This explains, in part, why impotence is so common among long-term smokers, diabetic men, and men with testosterone deficiency.

Male Sexual Chemistry and Viagra

// October 25th, 2010 // No Comments » // Impotence

From the moment Viagra came on the market, men, and women, too, have been intrigued by this new “potency pill.” In this chapter, you will find answers to many of the commonly asked questions about Viagra.

1. What is so special about Viagra?
2. Understanding male sexual chemistry: What makes Viagra work?
3. How does Viagra differ from other impotence treatments?
4. Is Viagra effective for every impotent man?
5. What are the side effects of Viagra?
6. Is there reason to fear Viagra?
7. Death after sex and/or Viagra: What is the risk?
8. What are the fantasies, fears, and reality of philandering after Viagra?
9. Can Viagra take the worry out of sex?
10. How can Viagra be used for maximum benefit and minimal risk?
11. The politics of male sexuality: Who will pay for Viagra?
12. Does Viagra work for women?
13. What’s next after Viagra?

His Cheshire cat smile, renewed vigor in stride, and different gaze — firm, straight-ahead, no longer oblique or downcast — tells me what I want to know before Michael opens his mouth.

“It worked!”

Eager to elaborate, he went on: “I took the pill around 9 P.M., watched a little TV, then in the middle of the 10 o’clock news decided to join my wife on the couch and started in like when we were first dating.”

“I’m waiting to hear the weather, she protested.”

“This will be more interesting than the weather,” I insisted, feeling myself starting to swell.”

“What’s gotten into you?” she wanted to know.”

“I’ll tell you later.”

Before long our clothes were off, we were in the bedroom, and my penis was firm. Then the more we played, the firmer it became. I could not remember the last time I was this powerful or excited. The more we played, the harder it got, and when we made love, it was exciting and wonderful, like it was before I had, you know my problem. Now I feel like a new man,” Michael enthused.

Michael and millions of men just like him, once impotent and fearful of entering into any sexual activity because of lingering doubts about whether they would be able to “perform” during sexual intimacy, can now look forward to enjoying sex once again, all because of a tiny blue pill.

In the past “the Pill” referred only to the oral contraceptive birth control pill. That “Pill” liberated women, allowing them to enjoy sex and be sexually active without fear of pregnancy. The new “Pill” is equally revolutionary because it deciphers the mystique of a man’s sexuality.

Maybe it was inevitable. Sooner or later someone had to solve the riddle of a man’s unique sexual chemistry. Once doctors knew what controls a man’s sexual urges and his ability to have sexual intercourse, they believed they would know all there was to know about men’s sexuality. For too many years, everyone, scientists and public included, attributed all male behavior to too much or too little testosterone. Now we know that testosterone is still important, even vital, for many male directed sexual behaviors. Indeed, today we have a better and much more sophisticated understanding of the promises and perils of this prototype male hormone.  But testosterone alone is not the whole story.

Men’s sexual chemistry depends on even more. Once scientists understood the chemical reactions involved in the transformation of a man’s penis from limp to erect, they could develop a “designer potency pill.” The goal was to recharge a man’s sexual batteries and make it possible for a man who, for one reason or another, had lost the ability to have sex to reclaim his manhood. Such a pill would allow a sexually impaired man to feel confident about his ability to have erections and take pleasure in sexual intercourse once again.

Over the years, many pills containing yohimbine, vitamin E, and zinc were hawked as male restoratives. Many are still used to bolster a man’s sexual appetite and power and continue to enjoy great popularity today. However, none of these oral medications achieved the immediate stardom or instantaneous success of sildenafil (Viagra).

From the beginning, the buzz on Viagra was extraordinary, like that for no other new drug in the history of medicine. Viagra’s FDA approval shouldered aside, at least temporarily, the public’s obsession with President Clinton and Monica Lewinsky. The prestigious column-one slot in the New York Times was devoted to FDA approval of this pill to treat impotence. Every major newspaper and news magazine followed suit, and overnight Viagra became a household word.