Pulmonary Arterial Hypertension (PAH)

As well as in ED (erectile dysfunction), sildenafil citrate is also effective in the rare disease pulmonary arterial hypertension (PAH). It works by relaxing the arterial wall, leading to decreased pulmonary arterial resistance and pressure. This in turn reduces the workload of the right ventricle of the heart and improves symptoms of right-sided heart failure. Because PDE-5 is primarily distributed within the arterial wall smooth muscle of the lungs and penis, sildenafil citrate acts selectively in both these areas without inducing vasodilation in other areas of the body. Sildenafil citrate was approved by FDA for this indication in June 2005. The preparation has name Revatio, to avoid confusion with Viagra, and the 20 milligram tablets are white and round. Sildenafil citrate joins the group of prostacyclin and bosentan (trade name: Tracleer) based therapies for this condition.

Raynaud’s Phenomenon Symptoms Relieve

In 2005, german researchers - Dr. Roland Fries and colleagues from Gotthard-Schettler-Klinik in Bad Schonborn, Germany, reported that in a small study of patients with severe Raynaud’s phenomenon who previously failed to respond to conventional treatment with vasodilators, sildenafil citrate significantly improved microcirculation and cut the frequency of Raynaud’s phenomenon attacks, reduced their duration by approximately one half, and more than quadrupled the mean capillary blood velocity. This was a double-blind, placebo-controlled crossover trial and the patients had both the primary and secondary forms and had all discontinued the more conventional treatments for this.

The report was published in the November issue of Circulation, a Journal of the American Heart Association - http://circ.ahajournals.org.

Other Non-medical Uses

Prevention of plant wilting

Israeli researcher Professor Yaacov Leshem reported that a low-concentration solution of sildenafil citrate in water significantly prolongs the time before cut flowers wilt. One experiment showed that Viagra could double the time before cut flowers wilted from one week to two weeks. The mechanism of action is similar to that in humans: nitric oxide (NO) leads to the production of cGMP whose degradation by PDE-5 is inhibited by sildenafil citrate.

Most common viagra side effects may include: headache, flushing of the face, sneezing, dyspepsia, prolonged erections.

Less common side effects that may temporary also occur are palpitations, photophobia, temporary visual changes like blurring of vision, increased light sensitivity, a tinge of vision with blue color.

In rare cases, patients taking Viagra or other PDE-5 inhibitors such as Cialis or Levitra reported a sudden decrease or loss of vision in one or both eyes. It is not possible to determine whether these events are related directly to these medications, to other factors such as high blood pressure or diabetes, or to a combination of these. If you notice sudden decrease or loss of vision, stop taking PDE-5 inhibitors including Viagra and contact your doctor immediately.

In very rare cases heart attack, stroke, irregular heart beats, and death have been reported in patients taking Viagra. Most of these patients had heart problems before taking this medicine. It is not possible to determine whether these incidents were directly related to Viagra.

In very rare cases, men have reported an erection that lasts many hours. If you ever have an erection that lasts more than 4 hours you should call your doctor immediately . If not treated instantly, permanent damage to your penis could occur.

if you are taking or have recently taken any nitrate medicines or medicines that contain nitrates such as e.g. isosorbide dinitrate - Isordil, Dilatrate, Sorbitrate, isosorbide mononitrate - Imdur, Ismo, Monit, Monoket, nitroglycerin - Nitro-BID, Nitro-Dur, Nitrostat, Nitroquick, you should not take Viagra. If you are not sure whether any of your medications contain nitrates, ask your doctor or pharmacist.

do not take “poppers” - street drugs containing nitrates such as amyl nitrate and butyl nitrate while taking viagra.

tell your doctor and pharmacist about all the medications that you are taking because there are some medications known to interact with Viagra.

tell your doctor if you are allergic to Viagra or any other medications.

tell your doctor and pharmacist what medications, vitamins, herbal products, supplements you are taking or you plan to take.

tell your doctor if you have ever had any heart problems or a stroke.

tell your doctor if you have low or high blood pressure.

if you are also taking protease inhibitors for the treatment of HIV you should know that protease inhibitors inhibit the metabolism of Viagra, effectively multiplying the plasma levels of viagra, increasing the incidence and severity of side effects. It is recommended that patients using protease inhibitors limit their use of Viagra to no more than minimal single dose (25 mg) per 48 hours period.

you should know that Viagra is only for men and should not be used by women or children.

- take any medications that contain nitrates - either regularly or as needed.

If you take Viagra with any nitrate drug or recreational drug containing nitrates, your blood pressure could rapidly drop to an unsafe level. You could feel dizzy, faint, or even have a stroke or heart attack. Nitrates are found in many prescription medicines that are used to treat angina (chest pain due to heart disease) such as:

• • nitroglycerin (tablets that are swallowed or dissolved in the mouth, sprays, ointments, skin patches and pastes)
• • isosorbide mononitrate or isosorbide dinitrate (tablets that are swallowed, chewed, or dissolved in the mouth)

Nitrates are also found in recreational drugs such as amyl nitrate/nitrite or butyl nitrite (know commonly as “poppers”).

If you are not sure if any of your medicines contain nitrates, or if you do not understand what nitrates are, ask your doctor.

-have hypotension (low blood pressure)

-had stroke (cerebrovascular accident) or heart attack recently

-for whom sexual intercourse is inadvisable due to cardiovascular risk factors

-have severe hepatic impairment (decreased liver function)

-have severe impairment in renal function

-have hereditary degenerative retinal disorders (including genetic disorders of retinal phosphodiesterases)

Viagra must be used only under a doctor’s supervision. Only your doctor can tell you if you can take Viagra or not.

Viagra is only for men who suffer from erectile dysfunction. Viagra is not for children or women.

Overdosage: In cases of overdose, contact your doctor immediately.

If you take Viagra after a high-fat meal such as a pizza or french fries, the medicine may take a bit longer to start working because it slows the ability of your body to absorb the medicine. Also, drinking large amounts of alcohol can temporarily make the medicine less effective and affect the ability to get an erection.

Before you will decide to take the drug, we highly recommend you to consult your doctor.

By 1994, Nicholas Terrett and Peter Ellis discovered during the trial studies of sildenafil as a heart medicine that it also increased inflow of blood into the penis area, allowing men to reverse the lack of ability to get an erection. The drug acts by enhancing the smooth muscle relaxant effects of nitric oxide (NO), a chemical substance that is normally released in response to sexual stimulation. The smooth muscle relaxation allows increased blood flow into the penis leading to an erection when combined with something exciting.

The first phase of clinical trials under the direction of Ian Osterloh suggested that the drug had little effect on angina pectoris, but that it could induce significant penis erections.

Pfizer therefore decided to market it for anti-impotence drug, rather than for heart medication.

Finally, 21 randomized, placebo-controlled clinical trials including more than 3700 patients, ages 19 to 87 years, were held worldwide. The participants had varying degrees of impotence associated with the following:

• • diabetes
• • spinal cord injury
• • history of prostate surgery
• • no identifiable organic cause

Some group of patients also had coexisting illnesses, including hypertension and coronary artery disease.

The drug was patented in 1996 and the clinical trials found sildenafil citrate to be so effective, that the US Food and Drug (FDA) approved it for prescription sale only six months after submission (at the end of March, 1998), and without consulting an advisory committee of outside experts because there were no troubling questions and no significant side effects.

Made by Pfizer Pharmaceuticals, Viagra is the first approved non-surgical treatment for male impotence - erectile dysfunction that does not have to be either inserted or injected directly into the penis to achieve and keep an erection.

Viagra soon became a great success: annual sales of Viagra pills in the period 1999–2001 exceeded 1 billion US dollars. Viagra began to be considered as one of the highest money grossing prescription drugs it has ever produced.

The British Press portrayed Peter Dunn and Albert Wood as the inventors of the process by which the drug was created, a claim which Pfizer disputes. Their names appeared on an application by Pfizer Pharmaceuticals to patent (WOWO9849166A1) the manufacturing process of Viagra (sildenafil citrate). Peter Dunn and Albert Wood are both employees of Pfizer Pharmaceuticals at the Pfizer run research laboratories in Kent and employees are not allowed to discuss their status or non-status as inventors.

Although Viagra is only available by prescription from a doctor, it was advertised directly to consumers on US TV (famously being endorsed by former United States Senator Bob Dole and brazilian soccer star Pelé). Numerous websites on the Internet offer Viagra pills for sale after an “online consultation”, a mere web questionnaire. The “Viagra” name has become so well known that many fake aphrodisiacs now call themselves “herbal Viagra” or are presented as blue tablets imitating the shape and colour of Pfizer’s product. Viagra is also informally known as “the Magic Blue Pill”, “Vitamin V”, as well as many various other nicknames.

In February 2007, it was announced that Boots the Chemist would trial over the counter sales of Viagra in stores in Manchester, England. Men aged between 30 and 65 would be eligible to buy four tablets after a consultation with a pharmacist.

Pfizer’s worldwide patents on sildenafil citrate will expire in 2011–2013. The UK patent held by Pfizer on the use of PDE5 inhibitors as treatment of impotence was invalidated because of obviousness in 2000; this decision was upheld on appeal in 2002.

References:
^ Wikipedia.org Sildenafil Article.
^ Kling Jim. From hypertension to angina to Viagra. Modern Drug Discovery.

Viagra (sildenafil citrate) is a medication that works by increasing blood flow to the penis. Viagra enables many men with erectile dysfunction (impotence) problem to respond to sexual stimulation. When a man is sexually excited, Viagra helps the penis fill with enough blood to cause an erection. After sexual activity is over, the erection goes away.

Detailed Medical Explanation

Viagra is used to treat male erectile dysfunction (impotence) and pulmonary arterial hypertension (PAH). Part of the physiological process of erection involves the release of nitric oxide (NO) in the penile corpus cavernosum. This then activates the enzyme guanylate cyclase which results in increased levels of cyclic guanosine monophosphate (cGMP), leading to smooth muscle relaxation in the corpus cavernosum, resulting in increased blood flow to the penis and an erection. Viagra is a potent and selective inhibitor of cGMP specific phosphodiesterase type 5 (PDE5) which is responsible for degradation of cGMP in the corpus cavernosum. This means that, with Viagra on board, normal sexual stimulation results in increased levels of cGMP in the corpus cavernosum which leads to better erections. Without sexual stimulation and no activation of the NO/cGMP system, Viagra should not cause an erection.

Viagra inhibits the cGMP specific phosphodiesterase type 5 (PDE5) which is responsible for degradation of cGMP in the corpus cavernosum located around the penis. Penile erection during sexual stimulation is caused by increased penile blood flow resulting from the relaxation of penile arteries and corpus cavernosal smooth muscle. This response is mediated by the release of nitric oxide (NO) from nerve terminals and endothelial cells, which stimulates the synthesis of cGMP in smooth muscle cells. Cyclic GMP causes smooth muscle relaxation and increased blood flow into the corpus cavernosum. The inhibition of phosphodiesterase type 5 (PDE5) by Viagra enhances erectile function by increasing the amount of cGMP.

Other Brand/Trade Names: Caverta, Edegra, Kamagra, Meltabs, Silagra, Zenegra, Revatio (smaller doses of sildenafil citrate for treatment of pulmonary arterial hypertension -PAH) and many other names