Efficacy and Onset of Action for Sildenafil Treatment

"Generic Viagra: Two versions of sildenafil hit the market today". Archived from the original on 25 November 2018. Archived from the original on 12 February 2022.

• Sildenafil works by relaxing blood vessels in the penis.
• This increases blood flow, aiding in achieving and maintaining an erection.
• The mechanism is similar for pulmonary hypertension in the lungs.
• It inhibits the PDE5 enzyme, which regulates blood flow.
• Effects can last for up to four to five hours.
• It does not cause automatic erections; sexual arousal is necessary.
• Tolerance or dependence on the drug is not typically reported.

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U.S. Food and Drug Administration (FDA). Archived from the original on 31 March 2021. Archived from the original on 12 August 2025. ^ "Sildenafil Drug Usage Statistics, United States, 2014 - 2023". "Phosphodiesterase inhibitors for erectile dysfunction in patients with diabetes mellitus".

• Sildenafil is metabolized primarily by the liver enzyme CYP3A4.
• Drugs that inhibit this enzyme can increase sildenafil levels and side effects.
• Examples include some antibiotics, antifungals, and HIV medications.
• Drugs that induce CYP3A4 can decrease sildenafil's effectiveness.
• Always provide your doctor with a complete list of your medications.
• This includes over-the-counter drugs, herbs, and supplements.
• Pharmacists perform interaction checks before dispensing.

"Strategies for managing sexual dysfunction induced by antidepressant medication".

The Cochrane Database of Systematic Reviews (5) CD003382. Archived from the original on 10 October 2020. "Efficacy and safety of sildenafil treatment in pulmonary arterial hypertension: a systematic review". Archived from the original on 29 August 2021. "Raynaud's phenomenon and digital ischaemia--pharmacologic approach and alternative treatment options". "Efficacy of Sildenafil on healthy humans in high‑altitude hypoxia at rest and during exercise: A meta‑analysis". "Interventions for preventing high altitude illness: Part 1. Archived from the original on 10 June 2017.

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Archived from the original on 11 October 2020. Archived from the original on 11 November 2020. ^ Nichols DJ, Muirhead GJ, Harness JA (6 March 2002). "Pharmacokinetics of sildenafil after single oral doses in healthy male subjects: absolute bioavailability, food effects and dose proportionality". The American Society of Health-System Pharmacists.

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Archived from the original on 23 April 2020. PDE-5 inhibitors appear to have significant but moderate efficacy in secondary [Raynaud's phenomenon]. "Sublingual sildenafil in the treatment of erectile dysfunction: faster onset of action with less dose". "The Serendipitous Story of Sildenafil: An Unexpected Oral Therapy for Erectile Dysfunction". ^ "Drug Approval Package: Viagra (sildenafil citrate) NDA #020895". ^ "FDA Updates Labeling for Viagra, Cialis and Levitra sildenafil softgel capsule for Rare Post-Marketing Reports of Eye Problems" (Press release).

• Sildenafil should be taken as directed, usually 30-60 minutes before sexual activity.
• Do not crush, chew, or break the tablet; swallow it whole with water.
• Taking it with a high-fat meal can delay the onset of action.
• Avoid consuming grapefruit or grapefruit juice while using sildenafil.
• Grapefruit can increase the level of sildenafil in your bloodstream.
• This raises the risk of side effects.
• Stick to the prescribed schedule and do not take extra doses.

Archived from the original on 22 October 2016. "Vision disorders and phosphodiesterase type 5 inhibitors: a review of the evidence to date". ^ "FDA Announces Revisions to Labels for Cialis, Levitra and Viagra". "Drug interactions with phosphodiesterase-5 inhibitors used for the treatment of erectile dysfunction or pulmonary hypertension". "Pharmacology and drug interaction effects of the phosphodiesterase 5 inhibitors: focus on alpha-blocker interactions". Use of sildenafil (Viagra) in patients with cardiovascular disease. American College of Cardiology/American Heart Association".

Journal of the American College of Cardiology. ^ "Viagra (Sildenafil Citrate): Side Effects, Interactions, Warning, Dosage & Uses". Archived from the original on 12 July 2018.

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Pfizer Canada Inc., pointed to section 27(3)(b) of The Patent Act which requires that disclosure must include sufficient information "to enable any person skilled in the art or science to which it pertains" to produce it. It added further: "As a matter of policy and sound statutory interpretation, patentees cannot be allowed to 'game' the system in this way. This, in my view, is the key issue in this appeal. Teva Canada launched Novo-Sildenafil, a generic version of Viagra, on the day the Supreme Court of Canada released its decision. [109][110][111] To remain competitive, Pfizer then reduced the price of Viagra in Canada.

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[112] However, on 9 November 2012, Pfizer filed a motion for a re-hearing of the appeal in the Supreme Court of Canada,[113] on the grounds that the court accidentally exceeded its jurisdiction by voiding the patent. [114] Finally, on 22 April 2013, the Supreme Court of Canada sildenafil citrate tables invalidated Pfizer's patent altogether. Manufacture and sale of sildenafil citrate drugs is common in China, where Pfizer's patent claim is not widely enforced. Egypt approved Viagra for sale in 2002, but soon afterwards allowed local companies to produce generic versions of the drug, citing the interests of poor people who would not be able to afford Pfizer's price. In June 2013 Pfizer's patent on sildenafil citrate expired in some member countries of the European Union, including Austria, Denmark, France, Germany, Ireland, Italy, The Netherlands, Spain, Sweden, the United Kingdom, and Switzerland. "Young men add Viagra to their drug arsenal". Archived from the original on 4 September 2014. "Recreational use and misuse of phosphodiesterase 5 inhibitors". Archived from the original on 21 August 2016. "Sildenafil does not improve sexual function in men without erectile dysfunction but does reduce the postorgasmic refractory time". ^ McCambridge J, Mitcheson L, Hunt N, Winstock A (March 2006). "The rise of Viagra among British illicit drug users: 5-year survey data".

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This patent was published in 2002 and expired in 2019. Teva sued to have the latter patent invalidated, but Pfizer prevailed in an August 2011 federal district court case. [100] An agreement with Pfizer allowed Teva to begin to provide the generic drug in December 2017. In the United States, Pfizer received two patents for sildenafil: one for its indication to treat cardiovascular disease (marketed as Revatio) and another for its indication to treat erectile dysfunction (marketed as Viagra). The substance is the same under both brand names.

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Sildenafil is available as a generic drug in the United States, labeled for pulmonary arterial hypertension,[98] and to treat erectile dysfunction, as the patent expired in April 2020. In the US, Revatio and Viagra are marketed by Viatris after Upjohn was spun off from Pfizer. In Canada, Pfizer's patent 2,324,324 for Revatio (sildenafil used to treat pulmonary hypertension) was found invalid by the Federal Court in June 2010, on an application by Ratiopharm Inc.[106][107] On 8 November 2012, the Supreme Court of Canada ruled that Pfizer's patent 2,163,446 on Viagra was invalid from the beginning because the company did not provide full disclosure in its application. The decision, Teva Canada Ltd. v. "Does marijuana use play a role in the recreational use of sildenafil?". Archived from the original on 26 January 2013. "Sildenafil accelerates reentrainment of circadian rhythms after advancing light schedules". Proceedings of the National Academy of Sciences of the United States of America.

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An October 2023 release stated that erectile dysfunction medicines were the most seized drugs by the Interpol[92] accounting for 22% of seizures. In 1992, Pfizer filed a patent covering the substance sildenafil and its use to treat cardiovascular diseases. [96] This would be marketed as Revatio. The patent was published in 1993 and expired in 2012. The patent on Revatio (indicated for pulmonary arterial hypertension rather than erectile dysfunction) expired in late 2012.

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Generic versions of this low-dose form of sildenafil have been available in the US from a number of manufacturers, including Greenstone, Mylan, and Watson, since early 2013. [97] Health care providers may prescribe generic sildenafil for erectile dysfunction. [98] For a time, the generic was not available in the same dosages as branded Viagra, so using dosages typically required for treating ED required patients to take multiple pills. In 1994, Pfizer filed a patent covering the use of sildenafil to treat erectile dysfunction. [99] This would be marketed as Viagra. "Source: Roger Clemens, host of athletes pop Viagra to help onfield performance". Archived from the original on 14 August 2020.

• Psychological factors often contribute to erectile dysfunction.
• Sildenafil addresses the physical component but not psychological causes.
• Anxiety, depression, and relationship stress can affect performance.
• Combining medication with sex therapy or counseling can be very effective.
• Open communication with a partner is an important part of treatment.
• Success with medication can sometimes improve psychological confidence.
• A holistic approach to sexual health is often best.

"Bears' Brandon Marshall says some NFL players use Viagra .. on the Field". Archived from the original on 5 March 2016.

Route of administration

This development was credited largely "due to the introduction of generic products." Generic sildenafil became publicly available in May. Sales of PalPal by Hanmi Pharmaceuticals totalled ₩22 billion or about 86% the market share of Viagra that year. [125] By 2017, there were over 50 generic sildenafil pills available. During that year Viagra sales slumped to 38% that of Palpal. There were 2,958,199 prescriptions for Sildenafil in 2016 in England, compared with 1,042,431 in 2006.

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In 2018, Viagra Connect, a particular formulation of Sildenafil marketed by Pfizer, became available for sale without a prescription in the UK. Archived from the original on 12 October 2020. ^ "Viagra 25mg film-coated tablets Summary of sildenafil pills Product Characteristics (SmPC)". ^ "Viagra Connect 50 mg film-coated tablets Summary of Product Characteristics (SmPC)". Archived from the original on 13 August 2020. "Towards a decade of detecting new analogues of sildenafil, tadalafil and vardenafil in food supplements: a history, analytical aspects and health risks".

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[117][118][119] A 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. Manufacture and sale of sildenafil citrate drugs known as "generic Viagra" is common in India, where Pfizer's patent claim does not apply. Brand names include Kamagra (Ajanta Pharma), Silagra (Cipla), Edegra (Sun Pharmaceutical), Penegra (Zydus Cadila), Manly (Cooper Pharma) and Zenegra (Alkem Laboratories). Sildenafil was reclassified in New Zealand in 2014 so it could be bought over the counter from a pharmacist. It is thought that this reduced sales over the Internet and was safer as males could be referred for medical advice if appropriate.

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In 1999 South Korea granted two patents to Pfizer related to sildenafil. The first document guaranteed sole production and sale of the substance until 2012, while the second gave Pfizer the exclusive use to treating erectile dysfunction with sildenafil until 2014. [123] In 2011 Hanmi Pharmaceutical and CJ CheilJedang launched a suit against the exclusive use patent. The Korean Court system made a ruling against Pfizer in June 2012, allowing for the unhindered domestic production of generic prescription sildenafil. In 2012, Viagra lost its position as the top selling erectile dysfunction treatment in South Korea.