VIAGRA® (sildenafil citrate)

In July 2005, the US Food and Drug Administration (FDA) updated labeling for tadalafil (Cialis), vardenafil (Levitra), and sildenafil (Viagra) to reflect a small number of post-marketing reports of sudden vision loss, while acknowledging that "...it is not possible to determine whether these oral medicines for erectile dysfunction were the cause of the loss of eyesight or whether the problem is related to other factors such as high blood pressure or diabetes, or to a combination of these problems. "[25] A careful review of pooled data from clinical trials containing well documented information about the dose and duration of exposure to the drug for a large number of patients, yields no evidence for an increased risk of non-arteritic anterior ischemic optic neuropathy or other adverse ocular events associated with PDE5 inhibitor use. Rare but serious adverse effects found through postmarketing surveillance include prolonged erections, severe low blood pressure, myocardial infarction (heart attack), ventricular arrhythmias, stroke, increased intraocular pressure, and sudden hearing loss. [4] In October 2007, the FDA announced that the labeling for all PDE5 inhibitors, including sildenafil, required a more prominent warning of the potential risk of sudden hearing loss. Care should be exercised by people who are also taking protease inhibitors for the treatment of HIV infection. Protease inhibitors inhibit the metabolism of sildenafil, effectively multiplying the plasma levels of sildenafil, increasing the incidence and severity of side effects.

People who purchased Pfizer Viagra 50mg Tablet 2s also bought

The molecular structure of sildenafil is similar to that of cGMP and acts as a competitive binding agent of PDE5 in the corpus cavernosum, resulting in more cGMP and increased penile response to sexual stimulation. [49][51] Without sexual stimulation, and therefore lack of activation of the NO/cGMP system, sildenafil should not cause an erection. Other drugs that operate by the same mechanism include tadalafil (Cialis) and vardenafil (Levitra). Sildenafil is broken down in the liver by hepatic metabolism using cytochrome p450 enzymes, mainly CYP450 3A4 (major route), but also by CYP2C9 (minor route) hepatic isoenzymes. The major product of metabolisation by these enzymes is N-desmethylated sildenafil, which is metabolised further.

Erectile dysfunction

This metabolite also has an affinity for the PDE receptors, about 40% of that of sildenafil. Thus, the metabolite is responsible for about 20% of sildenafil's action. Sildenafil is excreted as metabolites predominantly in the feces (about 80% of administered oral dose) and to a lesser extent in the urine (around 13% of the administered oral dose). If taken with a high-fat meal, absorption is reduced; the time taken to reach the maximum plasma concentration increases by around one hour, and the maximum concentration itself is decreased by nearly one-third. When taken orally, sildenafil for erectile dysfunction results in an average time to onset of erections of 27 minutes (ranging from 12 to 70 minutes). Those using protease inhibitors are recommended to limit their use of sildenafil to no more than one 25 mg dose every 48 hours. [4] Other drugs that interfere with the metabolism of sildenafil include erythromycin and cimetidine, both of which can also lead to prolonged plasma half-life levels. The use of sildenafil and an α1 blocker (typically prescribed for hypertension or for urologic conditions, such as benign prostatic hypertrophy) at the same time may lead to low blood pressure, but this effect does not occur if they are taken at least 4 hours apart. Concomitant use of nitric oxide donors, organic nitrites and nitrates,[30] such as: nitroglycerinisosorbide mononitrateisosorbide dinitratesodium nitroprussidealkyl nitrites (commonly known as "poppers") Concomitant use of soluble guanylyl cyclase stimulators, such as riociguat Sildenafil should not be used if sexual activity is inadvisable due to underlying cardiovascular risk factors. Sildenafil's popularity with young adults has increased over the years.

Product	Dosage	Quantity + Bonus	Price
Viagra Generic	150mg	180 + 10 Pills	236.46€ 225.20€	Buy
Viagra Professional	100mg	120 + 4 Pills	262.83€ 250.31€	Buy
Viagra Generic	100mg	20 Pills	45.58€ 43.41€	Buy
Viagra Oral Jelly	100mg	10 Sachets	46.36€ 44.15€	Buy
Viagra Generic	200mg	360 + 10 Pills	481.98€ 459.03€	Buy
Viagra Generic	50mg	120 + 6 Pills	129.64€ 123.47€	Buy
Viagra Generic	50mg	60 + 4 Pills	83.93€ 79.93€	Buy
Viagra Professional	100mg	60 + 2 Pills	146.74€ 139.75€	Buy
Viagra Generic	100mg	30 + 4 Pills	60.91€ 58.01€	Buy
Viagra Generic	100mg	180 + 8 Pills	199.37€ 189.88€	Buy
Viagra Super Active	100mg	10 Pills	28.76€ 27.39€	Buy
Viagra Generic	25mg	360 + 10 Pills	213.68€ 203.50€	Buy
Viagra Soft Tabs	100mg	180 + 10 Pills	314.95€ 299.95€	Buy
Viagra Original	100mg	22 + 2 Pills	120.71€ 114.96€	Buy

[32] Sildenafil's brand name, Viagra, is widely recognized in popular culture, and the drug's association with treating erectile dysfunction has led to its recreational use.

Side Effects Of Pfizer Viagra 50mg Tablet 2s

Sublingual use of sildenafil for erectile dysfunction results in an average onset of action of 15 minutes and lasting for an average of 40 minutes. The preparation steps for synthesis of sildenafil are:[54] Methylation of 3-propylpyrazole-5-carboxylic acid ethyl ester with hot dimethyl sulfate Hydrolysis with aqueous sodium hydroxide (NaOH) to free acid Carboxamide formation with refluxing thionyl chloride/NH4OH Reduction of nitro group to amino group Sildenafil (compound UK-92,480) was synthesized by a group of pharmaceutical chemists led by Simon Campbell[55] working at Pfizer's Sandwich, Kent, research facility in England. It was initially studied for use in hypertension (high blood pressure) and angina pectoris (a symptom of ischaemic heart disease). [56] The first clinical trials were conducted in Morriston Hospital in Swansea. [57] Phase I clinical trials under the direction of Ian Osterloh suggested the drug had little effect on angina, but it could induce marked penile erections.

Label Warnings

[58][59] Pfizer therefore decided to market it for erectile dysfunction, rather than for angina; this decision became an often-cited example of drug repositioning. [60][61] The drug was patented in 1996, approved for use in erectile dysfunction by the FDA on 27 March 1998, becoming the first oral treatment approved to treat erectile dysfunction in the United States, and offered for sale in the United States later that year. [62] It soon became a great success: annual sales of Viagra peaked in 2008 at US$1.934 billion. In the US, even though sildenafil is available only by prescription from a doctor, it was advertised directly to consumers on TV (famously being endorsed by former United States Senator Bob Dole and football star Pelé). Numerous sites on the Internet offer Viagra for sale after an "online consultation", often a simple web questionnaire. [33] The reasons behind such use include the belief that the drug increases libido, improves sexual performance,[33] or permanently increases penis size. [34] Studies on the effects of sildenafil when used recreationally are limited, but suggest it has little effect when used by those who do not have erectile dysfunction. In one study, a 25 mg dose was shown to cause no significant change in erectile quality, but did reduce the postejaculatory refractory time. [35] This study also noted a significant placebo effect in the control group. Unprescribed recreational use of sildenafil and other PDE5 inhibitors is noted as particularly high among users of illegal drugs. [36] Sildenafil is sometimes used to counteract the effects of other substances, often illicit. [33] Some users mix it with methylenedioxymethamphetamine (MDMA, ecstasy), other stimulants, or opiates in an attempt to compensate for the common side effect of erectile dysfunction, a combination known as "sextasy", "rockin' and rollin'", "hammerheading", or "trail mix". [33] Mixing it with amyl nitrite, another vasodilator, is particularly dangerous and potentially fatal. The 2007 Ig Nobel Prize in aviation went to Patricia V. Agostino, Santiago A. Plano, and Diego A. Golombek of Universidad Nacional de Quilmes, Argentina, for their discovery that sildenafil helps treat jet lag recovery in hamsters. Professional athletes have been documented using sildenafil, believing the opening of their blood vessels will enrich priligy and viagra their muscles. In turn, they believe it will enhance their performances. Acetildenafil and other synthetic structural analogs of sildenafil which are PDE5 inhibitors have been found as adulterants in a number of "herbal" aphrodisiac products sold over-the-counter. [41] These analogs have not undergone any of the rigorous testing that drugs like sildenafil have passed, and thus have unknown side-effect profiles. [42] Some attempts have been made to ban these drugs, but progress has been slow so far, as, even in those jurisdictions that have laws targeting designer drugs, the laws are drafted to ban analogs of illegal drugs of abuse, rather than analogs of prescription medicines. However, at least one court case has resulted in a product being taken off the market. The US Food and Drug Administration (FDA) has banned numerous products claiming to be Eurycoma longifolia that, in fact, contain only analogs of sildenafil. [44][45][46] Sellers of such fake herbals typically respond by just changing the names of their products. Sildenafil and/or N-desmethylsildenafil, its major active metabolite, may be quantified in plasma, serum, or whole blood to assess pharmacokinetic status in those receiving the drug therapeutically, to confirm the diagnosis in potential poisoning victims, or to assist in the forensic investigation in a case of fatal overdose. Nitric oxide (NO) in the corpus cavernosum of the penis binds to guanylate cyclase receptors, which results in increased levels of cGMP, leading to smooth muscle relaxation (vasodilation) of the intimal cushions of the helicine arteries. This smooth muscle relaxation leads to vasodilation and increased inflow of blood into the spongy tissue of the penis, causing an erection. [49] Robert F.

Region	Units Sold (Millions)	Revenue (USD Millions)	Market Share (%)
North America	10	1500	40
Europe	8	1200	32
Asia-Pacific	6	900	18
Latin America	4	600	10

Furchgott, Ferid Murad, and viagra click and collect Louis Ignarro won the Nobel Prize in Physiology or Medicine in 1998 for their independent study of the metabolic pathway of nitric oxide in smooth muscle vasodilation. The molecular mechanism of smooth muscle relaxation involves the enzyme CGMP-dependent protein kinase, also known as PKG. This kinase is activated by cGMP and it phosphorylates multiple targets in the smooth muscle cells, namely myosin light chain phosphatase, RhoA, IP3 receptor, phospholipase C, and others. [50] Overall, this results in a decrease in intracellular calcium and desensitizing proteins to the effects of calcium, engendering smooth muscle relaxation. The molecular structure of sildenafil is similar to that of cGMP and acts as a competitive binding agent of PDE5 in the corpus cavernosum, resulting in more cGMP and increased penile response to sexual stimulation.

Lạm dụng

The 2007 Ig Nobel Prize in aviation went to Patricia V. Agostino, Santiago A. Plano, and Diego A. Golombek of Universidad Nacional de Quilmes, Argentina, for their discovery that sildenafil helps treat jet lag recovery in hamsters. Professional athletes have been documented using sildenafil, believing the opening of their blood vessels will enrich priligy and viagra their muscles.

Common Adverse Effects

In turn, they believe it will enhance their performances. Acetildenafil and other synthetic structural analogs of sildenafil which are PDE5 inhibitors have been found as adulterants in a number of "herbal" aphrodisiac products sold over-the-counter. [41] These analogs have not undergone any of the rigorous testing that drugs like sildenafil have passed, and thus have unknown side-effect profiles. [42] Some attempts have been made to ban these drugs, but progress has been slow so far, as, even in those jurisdictions that have laws targeting designer drugs, the laws are drafted to ban analogs of illegal drugs of abuse, rather than analogs of prescription medicines. However, at least one court case has resulted in a product being taken off the market. [49][51] Without sexual stimulation, and therefore lack of activation of the NO/cGMP system, sildenafil should not cause an erection. Other drugs that operate by the same mechanism include tadalafil (Cialis) and vardenafil (Levitra).

• Viagra's quick onset makes it popular among users seeking spontaneity.
• The drug's contraindications include certain heart and eye conditions.
• Pfizer has developed generic versions when patents expired.
• Patients are advised to avoid high-fat meals to improve absorption.
• Viagra's use has expanded to include off-label pregnancy-related studies.
• The medication has been subject to numerous advertising campaigns.
• Pfizer invested in extensive post-marketing surveillance for Viagra.
• The safety profile of Viagra has been confirmed through long-term studies.
• Viagra influenced the rise of a broader market for sexual health drugs.

Sildenafil is broken down in the liver by hepatic metabolism using cytochrome p450 enzymes, mainly CYP450 3A4 (major route), but also by CYP2C9 (minor route) hepatic isoenzymes. The major product of metabolisation by these enzymes is N-desmethylated sildenafil, which is metabolised further.

• Sildenafil, the active compound in Viagra, was discovered in 1989.
• Pfizer's Viagra was initially marketed as a treatment for angina.
• Pfizer's marketing campaigns made Viagra a household name globally.
• The drug's efficacy was reinforced by numerous clinical trials.
• Viagra has been associated with a boost in male confidence and sexual satisfaction.
• The pill is available in different forms, including oral tablets.
• Pfizer faced legal challenges due to marketing practices for Viagra.
• The drug's popularity led to increased interest in ED and its treatment.
• Viagra's patented form was initially exclusive to Pfizer before generics emerged.

This metabolite also has an affinity for the PDE receptors, about 40% of that of sildenafil.

Viagra side effects

Can I take Viagra in my twenties?

Thus, the metabolite is responsible for about 20% of sildenafil's action. Sildenafil is excreted as metabolites predominantly in the feces (about 80% of administered oral dose) and to a lesser extent in the urine (around 13% of the administered oral dose). If taken with a high-fat meal, absorption is reduced; the time taken to reach the maximum plasma concentration increases by around one hour, and the maximum concentration itself is decreased by nearly one-third. When taken orally, sildenafil for erectile dysfunction results in an average time to onset of erections of 27 minutes (ranging from 12 to 70 minutes). Sublingual use of sildenafil for erectile dysfunction results in an average onset of action of 15 minutes and lasting for an average of 40 minutes. The preparation steps for synthesis of sildenafil are:[54] Methylation of 3-propylpyrazole-5-carboxylic acid ethyl ester with hot dimethyl sulfate Hydrolysis with aqueous sodium hydroxide (NaOH) to free acid Carboxamide formation with refluxing thionyl chloride/NH4OH Reduction of nitro group to amino group Sildenafil (compound UK-92,480) was synthesized by a group of pharmaceutical chemists led by Simon Campbell[55] working at Pfizer's Sandwich, Kent, research facility in England. It was initially studied for use in hypertension (high blood pressure) and angina pectoris (a symptom of ischaemic heart disease). [56] The first clinical trials were conducted in Morriston Hospital in Swansea.

What happens if I overdose?

Sildenafil's popularity with young adults has increased over the years. [32] Sildenafil's brand name, Viagra, is widely recognized in popular culture, and the drug's association with treating erectile dysfunction has led to its recreational use. [33] The reasons behind such use include the belief that the drug increases libido, improves sexual performance,[33] or permanently increases penis size. [34] Studies on the effects of sildenafil when used recreationally are limited, but suggest it has little effect when used by those who do not have erectile dysfunction. In one study, a 25 mg dose was shown to cause no significant change in erectile quality, but did reduce the postejaculatory refractory time.

What strengths does Viagra come in?

[35] This study also noted a significant placebo effect in the control group. Unprescribed recreational use of sildenafil and other PDE5 inhibitors is noted as particularly high among users of illegal drugs. [36] Sildenafil is sometimes used to counteract the effects of other substances, often illicit. [33] Some users mix it with methylenedioxymethamphetamine (MDMA, ecstasy), other stimulants, or opiates in an attempt to compensate for the common side effect of erectile dysfunction, a combination known as "sextasy", "rockin' and rollin'", "hammerheading", or "trail mix". [33] Mixing it with amyl nitrite, another vasodilator, is particularly dangerous and potentially fatal. [57] Phase I clinical trials under the direction of Ian Osterloh suggested the drug had little effect on angina, but it could induce marked penile erections. [58][59] Pfizer therefore decided to market it for erectile dysfunction, rather than for angina; this decision became an often-cited example of drug repositioning.

Non-medical use

The US Food and Drug Administration (FDA) has banned numerous products claiming to be Eurycoma longifolia that, in fact, contain only analogs of sildenafil. [44][45][46] Sellers of such fake herbals typically respond by just changing the names of their products. Sildenafil and/or N-desmethylsildenafil, its major active metabolite, may be quantified in plasma, serum, or whole blood to assess pharmacokinetic status in those receiving the drug therapeutically, to confirm the diagnosis in potential poisoning victims, or to assist in the forensic investigation in a case of fatal overdose. Nitric oxide (NO) in the corpus cavernosum of the penis binds to guanylate cyclase receptors, which results in increased levels of cGMP, leading to smooth muscle relaxation (vasodilation) of the intimal cushions of the helicine arteries. This smooth muscle relaxation leads to vasodilation and increased inflow of blood into the spongy tissue of the penis, causing an erection.

Elderly Precautions

[49] Robert F. Furchgott, Ferid Murad, and viagra click and collect Louis Ignarro won the Nobel Prize in Physiology or Medicine in 1998 for their independent study of the metabolic pathway of nitric oxide in smooth muscle vasodilation. The molecular mechanism of smooth muscle relaxation involves the enzyme CGMP-dependent protein kinase, also known as PKG. This kinase is activated by cGMP and it phosphorylates multiple targets in the smooth muscle cells, namely myosin light chain phosphatase, RhoA, IP3 receptor, phospholipase C, and others. [50] Overall, this results in a decrease in intracellular calcium and desensitizing proteins to the effects of calcium, engendering smooth muscle relaxation. [60][61] The drug was patented in 1996, approved for use in erectile dysfunction by the FDA on 27 March 1998, becoming the first oral treatment approved to treat erectile dysfunction in the United States, and offered for sale in the United States later that year. [62] It soon became a great success: annual sales of Viagra peaked in 2008 at US$1.934 billion. In the US, even though sildenafil is available only by prescription from a doctor, it was advertised directly to consumers on TV (famously being endorsed by former United States Senator Bob Dole and football star Pelé).

Tác dụng dược học

In July 2005, the US Food and Drug Administration (FDA) updated labeling for tadalafil (Cialis), vardenafil (Levitra), and sildenafil (Viagra) to reflect a small number of post-marketing reports of sudden vision loss, while acknowledging that "...it is not possible to determine whether these oral medicines for erectile dysfunction were the cause of the loss of eyesight or whether the problem is related to other factors such as high blood pressure or diabetes, or to a combination of these problems. "[25] A careful review of pooled data from clinical trials containing well documented information about the dose and duration of exposure to the drug for a large number of patients, yields no evidence for an increased risk of non-arteritic anterior ischemic optic neuropathy or other adverse ocular events associated with PDE5 inhibitor use. Rare but serious adverse effects found through postmarketing surveillance include prolonged erections, severe low blood pressure, myocardial infarction (heart attack), ventricular arrhythmias, stroke, increased intraocular pressure, and sudden hearing loss. [4] In October 2007, the FDA announced that the labeling for all PDE5 inhibitors, including sildenafil, required a more prominent warning of the potential risk of sudden hearing loss. Care should be exercised by people who are also taking protease inhibitors for the treatment of HIV infection.

Who should not take sildenafil?

Protease inhibitors inhibit the metabolism of sildenafil, effectively multiplying the plasma levels of sildenafil, increasing the incidence and severity of side effects. Those using protease inhibitors are recommended to limit their use of sildenafil to no more than one 25 mg dose every 48 hours. [4] Other drugs that interfere with the metabolism of sildenafil include erythromycin and cimetidine, both of which can also lead to prolonged plasma half-life levels. The use of sildenafil and an α1 blocker (typically prescribed for hypertension or for urologic conditions, such as benign prostatic hypertrophy) at the same time may lead to low blood pressure, but this effect does not occur if they are taken at least 4 hours apart. Concomitant use of nitric oxide donors, organic nitrites and nitrates,[30] such as: nitroglycerinisosorbide mononitrateisosorbide dinitratesodium nitroprussidealkyl nitrites (commonly known as "poppers") Concomitant use of soluble guanylyl cyclase stimulators, such as riociguat Sildenafil should not be used if sexual activity is inadvisable due to underlying cardiovascular risk factors. Numerous sites on the Internet offer Viagra for sale after an "online consultation", often a simple web questionnaire.

Condition	Warning Level	Reason
Uncontrolled hypertension	High	Risk of severe hypotension
Cardiovascular disease	High	Increased cardiac risk
Use of nitrate medications	High	Dangerous drop in blood pressure
Retinitis pigmentosa	Moderate	Potential retinal complications