Potential Side Effects and Safety Information for Canadian Patients

"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. "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.

• Sildenafil is also researched for potential use in pulmonary hypertension treatment.
• Canadian clinical trials have contributed to understanding sildenafil’s safety.
• Sildenafil’s use is contraindicated in individuals with certain heart conditions in Canada.
• Canadian health agencies monitor adverse reactions related to sildenafil usage.
• Education campaigns in Canada promote safe use of erectile dysfunction medications.

"Efficacy and safety of sildenafil treatment in pulmonary arterial hypertension: a systematic review". Archived from the original on 29 August 2021.

Adverse effects

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.

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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. "Raynaud's phenomenon and digital ischaemia--pharmacologic approach and sildenafil otc 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.

• Sildenafil's side effect profile requires medical supervision during treatment.
• Canadian pharmacists can advise on sildenafil storage and safe use.
• Education materials about sildenafil are available in multiple languages in Canada.
• Patients are encouraged to report any adverse effects to health authorities.
• Sildenafil should be used responsibly to prevent dependence or misuse in Canada.

^ "FDA Updates Labeling for Viagra, Cialis and Levitra for Rare Post-Marketing Reports of Eye Problems" (Press release).

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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 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.

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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. Archived from the original on 22 October 2016. "Vision disorders and phosphodiesterase type 5 inhibitors: a review of the evidence to date".

What is Viagra (Sildenafil)?

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 Announces Revisions to Labels for Cialis, Levitra and Viagra".

Who should avoid Viagra?

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". "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.

• 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.

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. "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". "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. "Source: Roger Clemens, host of athletes pop Viagra to help onfield performance". Archived from the original on 14 August 2020. "Bears' Brandon Marshall says some NFL players use Viagra .. on the Field". Archived from the original on 5 March 2016. "Towards a decade of detecting new analogues of sildenafil, tadalafil and vardenafil in food supplements: a history, analytical aspects and health risks". "Detection of sildenafil analogues in herbal products for erectile dysfunction".

• Sildenafil in Canada must meet strict quality standards set by health authorities.
• The typical recommended dose of sildenafil is 50 mg, adjustable based on response.
• Patients are advised to take sildenafil about an hour before planned activity.
• Sildenafil can be effective for up to 4-6 hours in maintaining erections.
• Combining sildenafil with alcohol or heavy meals may reduce its effectiveness.

Archived from the original on 4 March 2016. ^ "FDA Warns Consumers About Dangerous Ingredients in "Dietary Supplements" Promoted for Sexual Enhancement". Archived from the original on 18 January 2017. ^ "Hidden Risks of Erectile Dysfunction 'Treatments' Sold Online". Archived from the original on 23 April 2019. ^ R. Baselt, Disposition of Toxic Drugs and Chemicals in Man, 9th edition, Biomedical Publications, Seal Beach, CA, 2011, pp.

Talk to a licensed practitioner about Sildenafil online

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.

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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. Archived from the original (PDF) on 10 September 2011.

"Structure of the catalytic domain of human phosphodiesterase 5 with bound drug molecules". ^ a b Webb DJ, Freestone S, Allen MJ, Muirhead GJ (March 1999). "Sildenafil citrate and blood-pressure-lowering drugs: results of drug interaction studies with an organic nitrate and a calcium antagonist". ^ Goldstein I, Lue TF, Padma-Nathan H, Rosen RC, Steers WD, Wicker PA (May 1998). "Oral sildenafil in the treatment of erectile dysfunction. Archived from the original on 14 January 2012.

What are common side effects of Viagra?

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 Product Characteristics (SmPC)". ^ "Viagra Connect 50 mg film-coated tablets Summary of Product Characteristics (SmPC)". Archived from the original on 13 August 2020.

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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. "Onset and duration of action of sildenafil for the treatment of erectile dysfunction". ^ "Scientist who developed Viagra receives knighthood in New Year's Honours". Archived from the original on 14 January 2023. "Sildenafil: from angina to erectile dysfunction to pulmonary hypertension and beyond". Archived from the original on 26 September 2008. Our clinicians regularly offer patients the opportunity to take part in trials of new drugs and treatments.