Risks and Warnings Associated with Sildenafil Use

Archived from the original on 11 November 2020.

Medical uses

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. 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.

Low blood pressure

[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. This patent was published in 2002 and expired in 2019. ^ 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. 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".

Product 3. Auro-Sildenafil by Auro Pharma Canada

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. In 2018, Viagra Connect, a particular formulation of Sildenafil marketed by Pfizer, became available for sale without a prescription in the UK. ^ "Drug Approval Package: Viagra (sildenafil citrate) NDA #020895". U.S.

Food and Drug Administration (FDA).

• Storing sildenafil correctly maintains its potency and safety.
• Keep it at room temperature, away from excess heat and moisture.
• Do not store it in a bathroom cabinet due to humidity.
• Keep the medication in its original container with the label.
• Ensure the container is tightly closed and out of reach of children.
• Do not use sildenafil past its expiration date.
• Proper disposal at a pharmacy take-back program is recommended for unused pills.

Archived from the original on 31 March 2021. Archived from the original on 12 August 2025. ^ "Sildenafil Drug Usage Statistics, United States, 2014 - 2023". "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. "With Viagra Now Available Over-The-Counter In The U.K., Will The U.S.

How Viagra® Works

Archived from the original on 12 October 2020. ^ "Viagra 25mg film-coated tablets Summary of Product Characteristics (SmPC)". ^ "Viagra Connect 50 mg film-coated tablets Summary of Product Characteristics (SmPC)". Archived from the original on 13 August 2020. Archived from the original on 11 October 2020. "Phosphodiesterase inhibitors for erectile dysfunction in patients with diabetes mellitus". "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.

• 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.

"Raynaud's phenomenon and digital ischaemia--pharmacologic approach and alternative treatment options".

What is Sildenafil?

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. [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.

Guanylate Cyclase (GC) Stimulators

[114] Finally, on 22 April 2013, the Supreme Court of Canada 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. [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. "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. ^ "FDA Updates Labeling for Viagra, Cialis and Levitra for Rare Post-Marketing Reports of Eye Problems" (Press release). 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".

Hospital Affiliations

Manufacture and sale of sildenafil citrate drugs known white sildenafil tablets 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. In 1999 South Korea granted two patents to Pfizer related to sildenafil.

Sexually Transmitted Diseases

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. This development was credited largely "due to the introduction of generic products." Generic sildenafil became publicly available in May. "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".

Can you mix viagra and cialis

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. 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.

Serious Side Effects

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. 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. Journal of the American College of Cardiology. ^ "Viagra (Sildenafil Citrate): Side Effects, Interactions, Warning, Dosage & Uses".

Product 1. PRZ-sildenafil by Pharmaris Canada

Pfizer's patents on Viagra expired outside the US in 2012; in the US they were set to expire, but Pfizer settled litigation with each of Mylan and Teva which agreed that both companies could introduce generics in the US in December 2017. [79][80] In December 2017, Pfizer released its own generic version of Viagra. As of 2018[update], the US Food and Drug Administration has approved fifteen drug manufacturers to market generic sildenafil in the United States. Seven of these companies are based in India. The patent for Pfizer's Viagra sildenafil to treat erectile dysfunction expired in April 2020.

Product Reviews

In 2026 a chocolate syrup called Boner Bears from Lockout Supplements was recalled through the FDA because of it containing Sildenafil as an undisclosed ingredient. Counterfeit Viagra, despite generally being cheaper,[88] can contain harmful substances or substances that affect how Viagra works, such as blue printer ink, amphetamines, metronidazole, boric acid, and rat poison. Viagra is one of the world's most counterfeited medicines. [90][91] According to a 2012 Pfizer study, around 80% of sites claiming to sell Viagra were selling counterfeits. An October 2023 release stated that erectile dysfunction medicines were the most seized drugs by the Interpol[92] accounting for 22% of seizures.