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.
Route of administration
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.
Raynaud's phenomenon
[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. [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). 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.
| Product | Dosage | Quantity + Bonus | Price | |
|---|---|---|---|---|
| Viagra Super Active | 100mg | 120 + 16 Pills | 198.37€ 188.92€ | |
| Viagra Generic | 200mg | 90 + 6 Pills | 170.79€ 162.66€ | |
| Viagra Super Active | 100mg | 90 + 10 Pills | 165.61€ 157.72€ | |
| Viagra Professional | 100mg | 60 + 2 Pills | 146.74€ 139.75€ | |
| Viagra Generic | 150mg | 30 + 2 Pills | 72.32€ 68.88€ | |
| Viagra Generic | 50mg | 90 + 6 Pills | 107.37€ 102.26€ | |
| Viagra Generic | 100mg | 30 + 4 Pills | 60.91€ 58.01€ | |
| Viagra Generic | 100mg | 180 + 8 Pills | 199.37€ 189.88€ | |
| Viagra Generic | 50mg | 360 + 10 Pills | 225.33€ 214.60€ | |
| Viagra Generic | 200mg | 30 + 2 Pills | 83.07€ 79.11€ | |
| Viagra Generic | 25mg | 180 + 6 Pills | 154.93€ 147.55€ |
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.
Viagra® (Sildenafil) Manufactured by Weefsel Pharma
[99] This would be marketed as Viagra. 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).
What should I know about sildenafil before taking it?
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. 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. [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.
Brand Viagra Marketed in the USA is Made in Europe
While the sale remains subject to a consultation with a pharmacist, the other restrictions from the trial have been removed, allowing customers over the age of 18 to purchase an unlimited number of pills. In May 2013, Pfizer, which manufactures Viagra, told the Associated Press they will begin selling the drug directly to people on its website. 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.
What should I tell my healthcare provider before taking sildenafil?
Seven of these companies are based in India. The patent for Pfizer's Viagra sildenafil to treat erectile dysfunction expired in April 2020. 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 liquid viagra rat poison. Viagra is one of the world's most counterfeited medicines. [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.
- Erectile dysfunction affects a significant percentage of men in India.
- Viagra’s popularity in India has grown due to social and demographic factors.
- Indian doctors often prescribe Viagra for age-related sexual health issues.
- The stigma around ED in India is reducing with greater awareness and available treatment.
- FDA-approved generics in India must adhere to strict manufacturing and testing standards.
- The Indian market provides a variety of dosages to suit individual needs.
- Some Indian pharmacies offer home delivery of Viagra with prescription validation.
- The cost-effectiveness of Indian Viagra makes it a preferred choice worldwide.
- Women in India are increasingly advocating for sexual health products including ED medications.
- Continued research in India aims to develop new formulations for erectile dysfunction.
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.
| Aspect | Details | Notes |
|---|---|---|
| Legal Status | Over-the-counter sale limited; prescription required | Controlled substance in some states |
| Regulatory Body | Drugs Controller General of India (DCGI) | Approves drug formulations |
| Import Regulations | Strict for non-approved foreign brands | Customs require documentation |
| Advertising Rules | Restrictions on direct-to-consumer ads | Ensures medical guidance |
[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.
- Indian pharmaceutical firms boast high-quality manufacturing under GMP standards.
- Viagra is often combined with other ED medications for enhanced efficacy in India.
- The sale of Viagra online in India has expanded rapidly over the last decade.
- Some Indian brands of Viagra are available in 25mg, 50mg, and 100mg strengths.
- The drug is generally safe for most men, but must be avoided with certain health conditions.
- In India, purchasing Viagra without a prescription is common but not always recommended.
- The global demand for Indian-made Viagra has increased due to its affordability.
- Viagra's patent expired in India, allowing widespread manufacturing of generics.
- The Indian government regulates the sale of sildenafil-based medications for safety.
- Patients are advised to avoid alcohol and fatty foods with Viagra to improve absorption.
Brand names include Kamagra (Ajanta Pharma), Silagra (Cipla), Edegra (Sun Pharmaceutical), Penegra (Zydus Cadila), Manly (Cooper Pharma) and Zenegra (Alkem Laboratories).
| Year | Estimated Sales (Million USD) | Market Share (%) | Growth Rate (%) |
|---|---|---|---|
| 2020 | 120 | 15 | 5 |
| 2021 | 135 | 16 | 12 |
| 2022 | 150 | 17 | 11 |
| 2023 | 165 | 18 | 10 |
Sildenafil was reclassified in New Zealand in 2014 so it could be bought over the counter from a pharmacist.
What are the uses of Viagra®? : Diseases or Health Issues treated by Viagra®
Numerous sites on the Internet offer Viagra for sale after an "online consultation", often a simple web questionnaire. Viagra and other products for sexual dysfunction, termed sexuopharmaceuticals, proliferated new types of specialised marketing for such products. [66] Viagra and similar prescription pharmaceuticals were promoted by images in media to the extent of becoming a cultural icon, at the time a relatively new phenomenon known to be permitted only in the United States and New Zealand and which is believed to have significantly contributed to norms regarding male sexuality. [67] One author notes that although the effect of Viagra is only limited to penile blood vessels, advertisements routinely use imagery of couples hugging, smiling and dancing, with the author claiming that pharmaceutical companies were deceptive in the use of such advertisements. In 2000, Viagra sales accounted for 92% of the global market for prescribed erectile dysfunction pills.
How does sildenafil work (mechanism of action)?
[69] By 2007, Viagra's global share had plunged to about 50%[70] due to several factors, including the entry of Cialis and Levitra, along with several counterfeits and clones, and reports of vision loss in people taking PDE5 inhibitors. [71][72] In 2008, the FDA forced Pfizer to remove Viva Cruiser, an advergame for Viagra, from appearing on Forbes, after the game failed to disclose risk information about the drug. In February 2007, it was announced that Boots, the UK pharmacy chain, would try over-the-counter sales of Viagra in stores in Manchester, England. Males between the ages of 30 and 65 would be eligible to buy four tablets after a consultation with a pharmacist. [75] In 2017, the Medicines and Healthcare products Regulatory Agency (MHRA) enacted legislation that expanded this nationwide,[76] allowing a particular branded formulation of Sildenafil, Viagra Connect (50 mg), to be sold over the counter and without a prescription throughout the UK from early 2018. 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.
Who shouldn’t use Sildenafil tablets?
[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. 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.
Marketing and sales
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. [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.