Viagara
Viagara citrate, sold under the names viagara, Revatio and generically under various other names, is a drug used to treat male erectile dysfunction (impotence) and pulmonary arterial hypertension (PAH), developed by the pharmaceutical company Pfizer. viagara pills are blue and diamond-shaped with the words "Pfizer" on one side, and "VGR xx" (where xx stands for "25", "50" or "100", the dose of that pill in milligrams) on the other. Its primary competitors on the market are tadalafil (Cialis), and vardenafil (Levitra).
Contents
* 1 History
* 2 Mechanism of action
* 3 Dosage and price
* 4 Contraindications
* 5 Side effects
* 6 Other uses
o 6.1 Pulmonary hypertension
o 6.2 Raynaud's phenomenon
* 7 Drug abuses
o 7.1 Aphrodisiac
o 7.2 Recreational use
* 8 Chemical Synthesis
* 9 See also
* 10 Notes
* 11 External links
viagara History
viagara (compound UK-92,480) was synthesized by a group of pharmaceutical chemists working at Pfizer's Sandwich, Kent research facility. It was initially studied for use in hypertension (high blood pressure) and angina pectoris (a form of ischaemic cardiovascular disease). Phase I clinical trials under the direction of Ian Osterloh suggested that the drug had little effect on angina, but that it could induce marked penile erections.[1][2] Pfizer therefore decided to market it for erectile dysfunction, rather than for angina. The drug was patented in 1996, approved for use in erectile dysfunction by the Food and Drug Administration on March 27, 1998, becoming the first pill approved to treat erectile dysfunction in the United States, and offered for sale in the United States later that year.[3] It soon became a great success: annual sales of viagara in the period 1999–2001 exceeded $1 billion.
The British press portrayed Peter Dunn and Albert Wood as the inventors of the drug, a claim which Pfizer disputes.[4] Their names are on the manufacturing patent application drug, but Pfizer claims this is only for convenience.
viagara is available as blue pills with a characteristic shape
Enlarge
viagara is available as blue pills with a characteristic shape
Even though viagara is only available by prescription from a doctor, it was advertised directly to consumers on US TV (famously being endorsed by Bob Dole). Numerous sites on the Internet offer viagara for sale after an "online consultation", a mere web questionnaire. The "viagara" name has become so well known that many fake aphrodisiacs now call themselves "herbal viagara" or are presented as blue tablets imitating the shape and colour of Pfizer's product. viagara is also informally known as "Vitamin V", "the Blue Pill", as well as various other nicknames.
Pfizer's worldwide patents on viagara citrate will expire in 2011–2013. The UK patent held by Pfizer on the use of PDE5 inhibitors (see below) as treatment of impotence was invalidated in 2000 because of obviousness; this decision was upheld on appeal in 2002.
viagara Mechanism of action
Part of the physiological process of erection involves the parasympathetic nervous system causing the release of nitric oxide (NO) in the corpus cavernosum of the penis. NO binds to the receptors of the enzyme guanylate cyclase which results in increased levels of cyclic guanosine monophosphate (cGMP), leading to smooth muscle relaxation (vasodilation) in the corpus cavernosum, resulting in increased inflow of blood and an erection.
viagara is a potent and selective inhibitor of cGMP specific phosphodiesterase type 5 (PDE5) which is responsible for degradation of cGMP in the corpus cavernosum. The molecular structure of viagara is similar to that of cGMP and acts as a competitive binding agent of PDE5 in the corpus cavernosum, resulting in more cGMP and better erections. Without sexual stimulation, and therefore lack of activation of the NO/cGMP system, viagara should not cause an erection. Other drugs that operate by the same mechanism include tadalafil (Cialis®) and vardenafil (Levitra®).
viagara is metabolised by hepatic enzymes and excreted by both the liver and kidneys. If taken with a high fat meal, there may be a delay in absorption of viagara and the peak effect might be reduced slightly as the plasma concentration will be lowered.
viagara Dosage and price
As with all prescription drugs, proper dosage is at the discretion of a licensed medical doctor. The dose of viagara is 25 mg to 100 mg taken once per day between 30 minutes to 4 hours before sexual intercourse.
It is usually recommended to start with a dosage of 50 mg and then lower or raise the dosage as appropriate. The drug is sold in three dosages (25, 50, and 100 mg), all three costing about US$10 per pill. viagara is not scored and it is not advisable to cut it to change dosage since the active compound is not distributed homogenously in the tablet.
viagara Contraindications
Contraindications include:
* When taking nitric oxide donors, organic nitrites and nitrates, such as glyceryl trinitrate, sodium nitroprusside, amyl nitrite ("poppers")[5]
* In men for whom sexual intercourse is inadvisable due to cardiovascular risk factors
* Severe hepatic impairment (decreased liver function)
* Severe impairment in renal function
* Hypotension (low blood pressure)
* Recent stroke or heart attack
* Hereditary degenerative retinal disorders (including genetic disorders of retinal phosphodiesterases)
viagara Side effects
Amongst viagara's serious adverse effects are: priapism, severe hypotension, myocardial infarction, ventricular arrhythmias, sudden death, stroke and increased intraocular pressure.
Common side effects include sneezing, headache, flushing, dyspepsia, prolonged erections, palpitations and photophobia. Visual changes including blurring of vision and a curious bluish tinge have also been reported.
Care should be exercised by patients who are also taking Protease inhibitors for the treatment of HIV. Protease inhibitors inhibit the metabolism of viagara, effectively multiplying the plasma levels of viagara, increasing the incidence and severity of side-effects. It is recommended that patients using protease inhibitors limit their use of viagara to no more than one 25-mg dose every 48 hours.
Some viagara users have complained of blurriness and loss of peripheral vision. In May of 2005, the U.S. Food and Drug Administration found that viagara could lead to vision impairment[6] and a number of studies have linked viagara use with nonarteritic anterior ischemic optic neuropathy.[7][8][9][10][11][12]
When used with an alpha blocker, take them at least four hours apart to avoid hypotension.[13]
viagara Other uses
viagara Pulmonary hypertension
As well as erectile dysfunction, viagara citrate is also effective in the rare disease pulmonary arterial hypertension (PAH). It relaxes the arterial wall, leading to decreased pulmonary arterial resistance and pressure. This in turn reduces the workload of the right atrium 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, viagara acts selectively in both these areas without inducing vasodilation in other areas of the body. Pfizer submitted an additional registration for viagara to the FDA, and viagara was approved for this indication in June 2005. The preparation is named Revatio, to avoid confusion with viagara, and the 20 milligram tablets are white and round. viagara joins bosentan and prostacyclin-based therapies for this condition.[14]
viagara Raynaud's phenomenon
In 2005, Dr. Roland Fries and colleagues reported that viagara cut the frequency of Raynaud's phenomenon attacks, reduced their duration by roughly 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.[15]
viagara Drug abuses
viagara Aphrodisiac
viagara is commonly and increasingly used as an aphrodisiac. While there is no clinical evidence that it has aphrodisiac activity, many seem to believe it will improve sexual performance as well as erectile function and enhance the sexual experience that will occur
viagara Recreational use
viagara's popularity with young adults has increased over the years.[16] It is sometimes used recreationally. Some users mix viagara with methylenedioxymethamphetamine (MDMA, ecstasy), a combination known as Sextasy.
viagara Chemical Synthesis
The preparation steps for synthesis of viagara (viagara citrate) are as follows:
1. Methylation of 3-propylpyrazole-5-carboxylic acid ethyl ester with hot dimethyl sulfate.
2. Hydrolysis with aqueous NaOH to free acid.
3. Nitration with oleum/fuming nitric acid.
4. Carboxamide formation with refluxing thionyl chloride/NH4OH.
5. Reduction of nitro group to amino.
6. Acylation with 2-ethoxybenzoyl chloride.
7. Cyclization.
8. Sulfonation to the chlorosulfonyl derivative.
9. Condensation with 1-methylpiperazine.[17][18]
Contents
* 1 History
* 2 Mechanism of action
* 3 Dosage and price
* 4 Contraindications
* 5 Side effects
* 6 Other uses
o 6.1 Pulmonary hypertension
o 6.2 Raynaud's phenomenon
* 7 Drug abuses
o 7.1 Aphrodisiac
o 7.2 Recreational use
* 8 Chemical Synthesis
* 9 See also
* 10 Notes
* 11 External links
viagara History
viagara (compound UK-92,480) was synthesized by a group of pharmaceutical chemists working at Pfizer's Sandwich, Kent research facility. It was initially studied for use in hypertension (high blood pressure) and angina pectoris (a form of ischaemic cardiovascular disease). Phase I clinical trials under the direction of Ian Osterloh suggested that the drug had little effect on angina, but that it could induce marked penile erections.[1][2] Pfizer therefore decided to market it for erectile dysfunction, rather than for angina. The drug was patented in 1996, approved for use in erectile dysfunction by the Food and Drug Administration on March 27, 1998, becoming the first pill approved to treat erectile dysfunction in the United States, and offered for sale in the United States later that year.[3] It soon became a great success: annual sales of viagara in the period 1999–2001 exceeded $1 billion.
The British press portrayed Peter Dunn and Albert Wood as the inventors of the drug, a claim which Pfizer disputes.[4] Their names are on the manufacturing patent application drug, but Pfizer claims this is only for convenience.
viagara is available as blue pills with a characteristic shape
Enlarge
viagara is available as blue pills with a characteristic shape
Even though viagara is only available by prescription from a doctor, it was advertised directly to consumers on US TV (famously being endorsed by Bob Dole). Numerous sites on the Internet offer viagara for sale after an "online consultation", a mere web questionnaire. The "viagara" name has become so well known that many fake aphrodisiacs now call themselves "herbal viagara" or are presented as blue tablets imitating the shape and colour of Pfizer's product. viagara is also informally known as "Vitamin V", "the Blue Pill", as well as various other nicknames.
Pfizer's worldwide patents on viagara citrate will expire in 2011–2013. The UK patent held by Pfizer on the use of PDE5 inhibitors (see below) as treatment of impotence was invalidated in 2000 because of obviousness; this decision was upheld on appeal in 2002.
viagara Mechanism of action
Part of the physiological process of erection involves the parasympathetic nervous system causing the release of nitric oxide (NO) in the corpus cavernosum of the penis. NO binds to the receptors of the enzyme guanylate cyclase which results in increased levels of cyclic guanosine monophosphate (cGMP), leading to smooth muscle relaxation (vasodilation) in the corpus cavernosum, resulting in increased inflow of blood and an erection.
viagara is a potent and selective inhibitor of cGMP specific phosphodiesterase type 5 (PDE5) which is responsible for degradation of cGMP in the corpus cavernosum. The molecular structure of viagara is similar to that of cGMP and acts as a competitive binding agent of PDE5 in the corpus cavernosum, resulting in more cGMP and better erections. Without sexual stimulation, and therefore lack of activation of the NO/cGMP system, viagara should not cause an erection. Other drugs that operate by the same mechanism include tadalafil (Cialis®) and vardenafil (Levitra®).
viagara is metabolised by hepatic enzymes and excreted by both the liver and kidneys. If taken with a high fat meal, there may be a delay in absorption of viagara and the peak effect might be reduced slightly as the plasma concentration will be lowered.
viagara Dosage and price
As with all prescription drugs, proper dosage is at the discretion of a licensed medical doctor. The dose of viagara is 25 mg to 100 mg taken once per day between 30 minutes to 4 hours before sexual intercourse.
It is usually recommended to start with a dosage of 50 mg and then lower or raise the dosage as appropriate. The drug is sold in three dosages (25, 50, and 100 mg), all three costing about US$10 per pill. viagara is not scored and it is not advisable to cut it to change dosage since the active compound is not distributed homogenously in the tablet.
viagara Contraindications
Contraindications include:
* When taking nitric oxide donors, organic nitrites and nitrates, such as glyceryl trinitrate, sodium nitroprusside, amyl nitrite ("poppers")[5]
* In men for whom sexual intercourse is inadvisable due to cardiovascular risk factors
* Severe hepatic impairment (decreased liver function)
* Severe impairment in renal function
* Hypotension (low blood pressure)
* Recent stroke or heart attack
* Hereditary degenerative retinal disorders (including genetic disorders of retinal phosphodiesterases)
viagara Side effects
Amongst viagara's serious adverse effects are: priapism, severe hypotension, myocardial infarction, ventricular arrhythmias, sudden death, stroke and increased intraocular pressure.
Common side effects include sneezing, headache, flushing, dyspepsia, prolonged erections, palpitations and photophobia. Visual changes including blurring of vision and a curious bluish tinge have also been reported.
Care should be exercised by patients who are also taking Protease inhibitors for the treatment of HIV. Protease inhibitors inhibit the metabolism of viagara, effectively multiplying the plasma levels of viagara, increasing the incidence and severity of side-effects. It is recommended that patients using protease inhibitors limit their use of viagara to no more than one 25-mg dose every 48 hours.
Some viagara users have complained of blurriness and loss of peripheral vision. In May of 2005, the U.S. Food and Drug Administration found that viagara could lead to vision impairment[6] and a number of studies have linked viagara use with nonarteritic anterior ischemic optic neuropathy.[7][8][9][10][11][12]
When used with an alpha blocker, take them at least four hours apart to avoid hypotension.[13]
viagara Other uses
viagara Pulmonary hypertension
As well as erectile dysfunction, viagara citrate is also effective in the rare disease pulmonary arterial hypertension (PAH). It relaxes the arterial wall, leading to decreased pulmonary arterial resistance and pressure. This in turn reduces the workload of the right atrium 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, viagara acts selectively in both these areas without inducing vasodilation in other areas of the body. Pfizer submitted an additional registration for viagara to the FDA, and viagara was approved for this indication in June 2005. The preparation is named Revatio, to avoid confusion with viagara, and the 20 milligram tablets are white and round. viagara joins bosentan and prostacyclin-based therapies for this condition.[14]
viagara Raynaud's phenomenon
In 2005, Dr. Roland Fries and colleagues reported that viagara cut the frequency of Raynaud's phenomenon attacks, reduced their duration by roughly 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.[15]
viagara Drug abuses
viagara Aphrodisiac
viagara is commonly and increasingly used as an aphrodisiac. While there is no clinical evidence that it has aphrodisiac activity, many seem to believe it will improve sexual performance as well as erectile function and enhance the sexual experience that will occur
viagara Recreational use
viagara's popularity with young adults has increased over the years.[16] It is sometimes used recreationally. Some users mix viagara with methylenedioxymethamphetamine (MDMA, ecstasy), a combination known as Sextasy.
viagara Chemical Synthesis
The preparation steps for synthesis of viagara (viagara citrate) are as follows:
1. Methylation of 3-propylpyrazole-5-carboxylic acid ethyl ester with hot dimethyl sulfate.
2. Hydrolysis with aqueous NaOH to free acid.
3. Nitration with oleum/fuming nitric acid.
4. Carboxamide formation with refluxing thionyl chloride/NH4OH.
5. Reduction of nitro group to amino.
6. Acylation with 2-ethoxybenzoyl chloride.
7. Cyclization.
8. Sulfonation to the chlorosulfonyl derivative.
9. Condensation with 1-methylpiperazine.[17][18]
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