Viagra

Viagra
Mrgreen71 · CC BY-SA 3.0 · source
Name	Viagra
Caption	Sildenafil citrate tablets
Tradename	Viagra
Routes of administration	Oral
Class	Phosphodiesterase type 5 inhibitor
Legal status	Prescription only
Bioavailability	~40%
Onset	30–60 minutes
Duration	4–5 hours
Metabolism	Hepatic (CYP3A4, CYP2C9)
Elimination half-life	~4 hours
Excretion	Feces and urine

Viagra is a prescription medication whose active ingredient is sildenafil citrate, primarily prescribed to treat erectile dysfunction in adult males. It is used clinically to facilitate penile erection in response to sexual stimulation and has an approved indication for pulmonary arterial hypertension under a different brand name. The drug transformed treatment options for sexual dysfunction and stimulated broad discussion across medical, legal, and cultural arenas.

Medical uses

Viagra is indicated for erectile dysfunction in adult males and is prescribed following assessment by clinicians such as urologists, cardiologists, or primary care physicians. In practice, specialists reference guidelines from organizations including the American Urological Association, European Association of Urology, World Health Organization, National Institute for Health and Care Excellence, and national formularies when considering treatment. Off-label and related use has involved consultation with experts from institutions such as Mayo Clinic, Johns Hopkins Hospital, Cleveland Clinic, and academic centers like Harvard Medical School and Stanford University School of Medicine. For pulmonary arterial hypertension, sildenafil is marketed under another name and recommended in protocols endorsed by professional bodies like the European Society of Cardiology and the American College of Cardiology in conjunction with centers including Massachusetts General Hospital.

Mechanism of action

Sildenafil is a selective inhibitor of the enzyme phosphodiesterase type 5 (PDE5) present in vascular smooth muscle of the corpus cavernosum and pulmonary vasculature. The molecular pathway links to nitric oxide signaling described in landmark work from laboratories at institutions like University of Rochester, University of California, San Francisco, and Imperial College London, and builds on discoveries honored by the Nobel Prize in Physiology or Medicine. By attenuating PDE5 activity, sildenafil increases intracellular cyclic guanosine monophosphate (cGMP) levels, promoting smooth muscle relaxation and vasodilation; comparable biochemical frameworks are discussed in studies from Rockefeller University and Cold Spring Harbor Laboratory. Mechanistic investigations have been published in journals affiliated with publishers such as Nature Publishing Group, Elsevier, Wiley-Blackwell, and The Lancet.

Pharmacology

Pharmacokinetic and pharmacodynamic profiles were characterized during multicenter trials involving research sites including University College London, Mount Sinai Hospital, Karolinska Institute, and University of Sydney. Oral bioavailability is approximately 40% with peak plasma concentrations reached within 30–120 minutes; absorption is influenced by concomitant meals, as documented by investigators at University of Oxford and McGill University. Hepatic metabolism via cytochrome P450 isoenzymes CYP3A4 and CYP2C9 has implications for drug–drug interactions with agents from classes represented by companies and institutions such as Pfizer, Roche, GlaxoSmithKline, and hospitals reporting interactions with protease inhibitors, macrolide antibiotics, azole antifungals, and certain cardiovascular medications. Clinical pharmacology data were vetted by regulatory agencies including the U.S. Food and Drug Administration, the European Medicines Agency, and national regulators in countries represented by Health Canada and the Therapeutic Goods Administration.

Side effects and contraindications

Common adverse effects documented in clinical trials and postmarketing surveillance include headache, flushing, dyspepsia, nasal congestion, and visual disturbances; these findings were reported by investigators affiliated with centers such as Johns Hopkins University, University of Pennsylvania, and Karolinska Institute. Serious but rare events include priapism, sudden hearing loss, and non-arteritic anterior ischemic optic neuropathy, which have been reviewed in case series from institutions like Cleveland Clinic and Mayo Clinic. Contraindications include concurrent use of organic nitrates and certain nitric oxide donors, a risk profile emphasized by guidance from American Heart Association and European Society of Cardiology. Careful assessment is advised in patients with cardiovascular disease, and management often involves multidisciplinary teams spanning clinics such as Guy's and St Thomas' NHS Foundation Trust, Royal Free Hospital, and Veterans Affairs medical centers.

History and development

Sildenafil was discovered in the late 1980s and developed through clinical trials conducted by researchers at pharmaceutical companies and academic collaborators, including investigators working with teams linked to Pfizer and research sites such as Alderley Park and university hospitals in London and New York City. Initial studies targeted angina pectoris, with serendipitous observations of penile erection leading to trials focused on erectile dysfunction and subsequent regulatory submissions to agencies like the U.S. Food and Drug Administration and the European Medicines Agency. The drug's launch influenced patent litigation and market dynamics involving corporations and law firms across jurisdictions including the United States Court of Appeals, European patent offices, and commercial disputes documented in cases concerning multinational companies and generic manufacturers. Historical analyses appear in books and articles from publishers such as Oxford University Press, Harvard University Press, and periodicals including The New York Times, The Guardian, and The Lancet.

Society and culture

The medication had broad cultural impact, shaping public discourse on sexual health in media outlets like BBC News, CNN, The Wall Street Journal, and The New Yorker. It influenced celebrity commentary, advertising regulation debates handled by bodies such as the Federal Trade Commission and agencies in the European Union, and spawned discussions in bioethics forums at institutions like The Hastings Center and Kennedy Institute of Ethics. The market prompted development of generics and parallel importation issues involving manufacturers and pharmacies in countries represented by India, Brazil, Germany, China, and Canada. Public health campaigns about safe use have been organized by NGOs and professional societies including Planned Parenthood Federation of America, International Society for Sexual Medicine, and national health services such as NHS England. The drug also intersected with legal and sporting controversies overseen by organizations like the World Anti-Doping Agency and trade disputes adjudicated in forums such as the World Trade Organization.

Category:Drugs