Viagra, known generically as sildenafil citrate, is a medication primarily used to treat erectile dysfunction (ED) [1]. It functions by increasing blood flow to the penis during sexual stimulation [2]. The medication is manufactured by Pfizer [3].
How does Viagra work to treat erectile dysfunction?
Viagra works by inhibiting an enzyme called phosphodiesterase type 5 (PDE5) [4]. This enzyme is responsible for breaking down cyclic guanosine monophosphate (cGMP) [4]. By inhibiting PDE5, Viagra allows cGMP to accumulate, which in turn relaxes the smooth muscles in the blood vessels of the penis. This relaxation permits increased blood flow, facilitating an erection [4].
When will Viagra patents expire?
The original patent for sildenafil citrate expired in many markets around 2012 [5][6]. However, patent protection can be complex, involving multiple patents covering different aspects of the drug, formulation, and manufacturing [5]. DrugPatentWatch.com tracks these patents and their expiration dates [5].
Can generic versions of Viagra be sold before patent expiration?
Generally, generic versions of Viagra cannot be legally sold in major markets until the relevant patents expire and any other market exclusivity periods have ended [6]. The expiration of primary patents often opens the door for generic manufacturers to seek regulatory approval for their versions of the drug [6].
What are the main side effects of Viagra?
Common side effects of Viagra can include headache, flushing, nasal congestion, visual disturbances (such as blurred vision or color tinge), and indigestion [2][7]. Less common but more serious side effects can include priapism (a prolonged erection lasting more than four hours), sudden vision loss, and sudden hearing decrease or loss [7].
What other conditions is sildenafil used for?
Sildenafil, the active ingredient in Viagra, is also prescribed under the brand name Revatio to treat pulmonary arterial hypertension (PAH) [1][8]. In this context, it works by relaxing blood vessels in the lungs, reducing blood pressure and improving exercise capacity [8].
Who are the main competitors to Viagra?
The market for erectile dysfunction treatments includes other PDE5 inhibitors such as tadalafil (Cialis), vardenafil (Levitra), and avanafil (Stendra) [9]. These drugs work similarly by increasing blood flow but may differ in their onset of action, duration of effect, and side effect profiles [9].
What is the typical cost of Viagra and its generic versions?
The cost of Viagra can vary significantly depending on the dosage, quantity, and whether a prescription is filled with the brand-name drug or a generic equivalent [10]. Generic sildenafil is generally less expensive than brand-name Viagra [10]. Prices can also be influenced by insurance coverage and pharmacy pricing [10].
Are there any major clinical studies on Viagra's effectiveness?
Numerous clinical trials have demonstrated the effectiveness of Viagra in treating erectile dysfunction [11]. Studies typically evaluate its ability to achieve and sustain an erection sufficient for satisfactory sexual performance [11]. The reported success rates in clinical trials vary, but many men with ED experience significant improvements [11].
Sources:
[1] https://www.pfizer.com/products/product-detail/viagra
[2] https://www.nhs.uk/medicines/sildenafil/
[3] https://www.pfizer.com/
[4] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1070880/
[5] https://drugpatentwatch.com/
[6] https://drugpatentwatch.com/blog/viagra-patent-expiry/
[7] https://www.mayoclinic.org/drugs-supplements/sildenafil-oral-route/side-effects/drh-20066603
[8] https://www.fda.gov/drugs/postmarket-drug-safety-information-for-patients/sildenafil-revatio-important-safety-information
[9] https://www.urologyhealth.org/urology-a-to-z/e/erectile-dysfunction/treatment-for-erectile-dysfunction
[10] https://www.goodrx.com/viagra
[11] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC2785621/