Viagra" redirects here. For other uses, see Viagra (disambiguation).
Sildenafil
Clinical data
Pronunciation    /sɪlˈdɛnəfɪl/ sil-DEN-ə-fil
Trade names    Viagra, Revatio, others
AHFS/Drugs.com    Monograph
MedlinePlus    a699015
License data    

    EU EMA: by INN
    US DailyMed: Sildenafil

Pregnancy
category    

    AU: B1[1]

Routes of
administration    Oral (tablets), intravenous, sublingual
ATC code    

    G04BE03 (WHO)

Legal status
Legal status    

    AU: S4 (Prescription only)
    CA: ℞-only
    UK: P (Pharmacy medicines) / POM[2][3]
    US: ℞-only[4]
    EU: Rx-only[5][6]
    In general: ℞ (Prescription only)

Pharmacokinetic data
Bioavailability    41% (mean)[7]
Protein binding    ~96%
Metabolism    Liver: CYP3A4 (major route), CYP2C9 (minor route)
Metabolites    N-desmethylsildenafil (~50% potency for PDE5)
Onset of action    20 minutes
Elimination half-life    3–4 hours
Excretion    Feces (~80%), urine (~13%)[4]
Identifiers
IUPAC name
CAS Number    

    139755-83-2 check
    citrate: 171599-83-0 check

PubChem CID    

    135398744
    citrate: 135413523

DrugBank    

    DB00203 check
    citrate: DBSALT000347 check

ChemSpider    

    5023 check
    citrate: 56586 check

UNII    

    3M7OB98Y7H
    citrate: BW9B0ZE037 check

KEGG    

    D08514 check
    citrate: D02229 check

ChEBI    

    CHEBI:9139 check
    citrate: CHEBI:58987 check

ChEMBL    

    ChEMBL192 check
    citrate: ChEMBL1737 check

PDB ligand    

    VIA (PDBe, RCSB PDB)

CompTox Dashboard (EPA)    

    DTXSID6023579 Edit this at Wikidata

ECHA InfoCard    100.122.676 Edit this at Wikidata
Chemical and physical data
Formula    C22H30N6O4S
Molar mass    474.58 g·mol−1
3D model (JSmol)    

    Interactive image

SMILES
InChI
 ☒check (what is this?)  (verify)

Sildenafil, sold under the brand name Viagra, among others, is a medication used to treat erectile dysfunction and pulmonary arterial hypertension.[4][8] It is also sometimes used off-label for the treatment of certain symptoms in secondary Raynaud's phenomenon.[9] It is unclear if it is effective for treating sexual dysfunction in women.[8] It can be taken orally (swallowed by mouth), intravenously (injection into a vein), or sublingually (dissolved under the tongue).[8][10] Onset when taken orally is typically within twenty minutes and lasts for about two hours.[8]

Common side effects include headaches, heartburn, and flushed skin.[8] Caution is advised in those with cardiovascular disease.[8] Rare but serious side effects include vision problems, hearing loss, and prolonged erection (priapism) that can lead to damage to the penis.[8] Sildenafil should not be taken by people on nitrates such as nitroglycerin (glycerin trinitrate), as this may result in a serious drop in blood pressure.[8] Sildenafil should not be taken within four hours of taking an alpha blocker.

Sildenafil acts by blocking phosphodiesterase 5 (PDE5), an enzyme that promotes breakdown of cGMP, which regulates blood flow in the penis.[8] It requires sexual arousal to work, and does not by itself cause or increase sexual arousal.[8] It also results in dilation of the blood vessels in the lungs.[8]

Pfizer originally discovered the medication in 1989 while looking for a treatment for angina.[11] It was approved for medical use in the United States and in the European Union in 1998.[5][8][11][12] In 2020, it was the 183rd most commonly prescribed medication in the United States, with more than 2 million prescriptions.[13][14] It is available as a generic medication.[15][16] In the United Kingdom, it is available over the counter.[17] Most of the active pharmaceutical ingredient, sildenafil citrate, is produced in Pfizer's Ringaskiddy complex in County Cork, Ireland, which is Pfizer's largest production facility outside of the United States.[18]
Medical uses
Pfizer Viagra tablet in the trademark blue diamond shape
Sexual dysfunction

The primary indication of sildenafil is treatment of erectile dysfunction (inability to sustain a satisfactory erection to complete sexual intercourse). Its use is now one of the standard treatments for erectile dysfunction, including for men with diabetes mellitus.[19]
Antidepressant-associated sexual dysfunction

Tentative evidence suggests that sildenafil may help men who experience antidepressant-induced erectile dysfunction.[20]
Pulmonary hypertension

While sildenafil improves some markers of disease in people with pulmonary arterial hypertension, it does not appear to affect the risk of death or serious side effects.[21]
Raynaud's phenomenon

Sildenafil and other PDE5 inhibitors are used off-label to alleviate vasospasm and treat severe ischemia and ulcers in fingers and toes for people with secondary Raynaud's phenomenon;[9][22] these drugs have moderate efficacy for reducing the frequency and duration of vasospastic episodes.[9] As of 2016, their role more generally in Raynaud's was not clear.[22]
High-altitude pulmonary edema

Sildenafil has been studied for high-altitude pulmonary edema, but its use is currently not recommended for that indication.[23]