--- title: "Sildenafil: Research & Side Effects | BodyHackGuide" url: https://www.bodyhackguide.co/compound/sildenafil description: "Sildenafil: mechanism, clinical studies & side effects." lang: en --- Skip to content Compare notes on r/BodyHackGuide (https://reddit.com/r/bodyhackguide) Compare notes with other researchers. Join r/BodyHackGuide (https://reddit.com/r/bodyhackguide) # Sildenafil Pharmaceutical: https://www.bodyhackguide.co/wiki#cat-pharmaceutical Status Approved (prescription) Evidence Not graded on a research bench yet Sildenafil is a phosphodiesterase type 5 (PDE5) inhibitor developed by Pfizer at its research center in Sandwich, England, and approved by the FDA as Viagra for erectile dysfunction on 27 March 1998 and as Revatio for pulmonary arterial hypertension on 3 June 2005. Reviewed 4 November 2026 01 Overview ## What Sildenafil is In a 1998 trial in men with erectile dysfunction, 69 percent of attempts at intercourse succeeded on sildenafil against 22 percent on placebo, and in a 278-person trial in pulmonary arterial hypertension sildenafil raised six-minute walk distance by 45 to 50 meters more than placebo (PMID: 9580646, PMID: 16291984). Sildenafil missed its primary endpoints in trials of heart failure with preserved ejection fraction and of severe fetal growth restriction, and a Dutch trial in pregnancy was halted after more newborns in the sildenafil group developed pulmonary hypertension (PMID: 23478662, PMID: 30169244, PMID: 32585017). The US labels contraindicate sildenafil with nitrates and with the guanylate cyclase stimulator riociguat, and they warn about low blood pressure, priapism, sudden vision loss and sudden hearing loss (US prescribing information for Viagra and Revatio). ### How it works ### How PDE5 inhibition works During sexual stimulation, nitric oxide released in the corpus cavernosum activates the enzyme guanylate cyclase, which raises cyclic guanosine monophosphate (cGMP) and relaxes smooth muscle so that blood flows into the penis (US prescribing information for Viagra). Sildenafil blocks phosphodiesterase type 5 (PDE5), the enzyme that breaks down cGMP in this tissue, so sildenafil amplifies the nitric oxide signal; the label states that sildenafil has no direct relaxing effect on isolated human corpus cavernosum and, at recommended doses, no effect without sexual stimulation (US prescribing information for Viagra). Organic nitrates also act by raising cGMP, and sildenafil potentiates their blood pressure lowering effect (PMID: 10078539; US prescribing information for Viagra). Read the full mechanism Show less In laboratory tests at Pfizer, sildenafil inhibited PDE5 from human penile tissue with a 50 percent inhibitory concentration (IC50) of 3.5 nanomolar, was 80 to more than 8,500 times weaker against PDE1 to PDE4, and was only about 9 times weaker against PDE6, the light-sensing enzyme of the retina, which in this study came from cow retina rather than human tissue (PMID: 9598563). The label states that this lower selectivity is thought to be the basis of the changes in color vision some users report (US prescribing information for Viagra). ### The lung and other tissues PDE5 is also found in platelets, vascular and visceral smooth muscle, skeletal muscle, lung, heart, brain, prostate and other tissues (US prescribing information for Viagra). In the lung, cGMP signaling relaxes vascular smooth muscle and slows its growth, the rationale given for testing sildenafil in pulmonary arterial hypertension (PMID: 16291984). In 14 healthy mountaineers, sildenafil lowered pulmonary artery pressure at rest and during exercise while they breathed low-oxygen air and again at Mount Everest base camp (PMID: 15289213). ### Absorption, breakdown and duration The absolute oral bioavailability of sildenafil was 41 percent in healthy men, in whom food delayed peak levels by about an hour and lowered the peak concentration by 29 percent (PMID: 11879254). Sildenafil is cleared mainly by the liver enzyme CYP3A4, with CYP2C9 as a minor route, and its main circulating metabolite, N-desmethyl sildenafil, has about half the PDE5 potency of the parent drug and accounts for about 20 percent of its effect (US prescribing information for Viagra). In a 1999 Pfizer study, the elimination half-life in humans was 3.7 hours, and no unchanged drug was detected in human excreta (PMID: 10219969). In two crossover studies in men with erectile dysfunction, erections began a median of 27 minutes after a 50 mg dose, and the authors reported a duration of action of at least 4 hours (PMID: 11879261). ### Studied for - Erectile dysfunction - Pulmonary arterial hypertension - Cardiovascular pharmacology - Sexual medicine - High-altitude physiology - Pharmacoepidemiology - Maternal-fetal medicine ### Benefits listed - Erectile function scores and successful intercourse attempts in placebo-controlled trials (PMID: 9580646) - Improved erections in a 268-man trial in men with diabetes (PMID: 9952201) - Six-minute walk distance in adults with pulmonary arterial hypertension (PMID: 16291984) - Time to clinical worsening when added to intravenous epoprostenol in pulmonary arterial hypertension (PMID: 18936500) Show 3 more Show less - Sexual function ratings in men and women taking serotonergic antidepressants (PMID: 12503977, PMID: 18647982) - Exercise capacity in low-oxygen conditions in 14 mountaineers (PMID: 15289213) - Frequency and duration of Raynaud attacks in a 16-patient crossover trial (PMID: 16275885) 02 Research Free with email ## What the research shows No research bench grades Sildenafil yet. Benches compare compounds people pair, with the evidence for each. ### Unlock the research summary Enter your email to keep reading. It is free, and it opens these sections on every compound page in this browser. - A summary of the key research - Safety and side effects - A link to the PubMed results You also get the free peptide cheat sheet by email. Unsubscribe anytime. Have an account? Sign in (https://www.bodyhackguide.co/auth) 03 Safety ## Sildenafil side effects and interactions ### Side effects #### Common - Headache in 16 to 28 percent of men in fixed-dose erectile dysfunction trials, against 7 percent on placebo - Flushing - Indigestion (dyspepsia) - Stuffy nose - Temporary color tinge, light sensitivity or blurred vision, most often at the highest dose in fixed-dose trials (US prescribing information for Viagra) - Nosebleeds, mainly in pulmonary arterial hypertension linked to connective tissue disease #### Serious events - Severe drop in blood pressure with nitrates (contraindicated) - Priapism - Sudden vision loss (NAION) reported with PDE5 inhibitors - Sudden decrease or loss of hearing reported with PDE5 inhibitors - Higher mortality at the high dose in a pediatric pulmonary arterial hypertension extension study (PMID: 24637559) - Pulmonary hypertension in newborns in a trial in pregnancies with fetal growth restriction (PMID: 32585017) ### Who should not use it Contraindications Sildenafil is contraindicated with nitrates and nitric oxide donors (organic nitrates or nitrites in any form, taken regularly or intermittently), because it potentiates their blood pressure lowering effect, and the label states that it is unknown when nitrates can be given safely after a dose of sildenafil (US prescribing information for Viagra; PMID: 10078539). Read all the contraindications and cautions Show less Sildenafil is contraindicated with guanylate cyclase stimulators such as riociguat, because PDE5 inhibitors may add to their blood pressure lowering effect (US prescribing information for Viagra and Revatio). Known hypersensitivity to sildenafil or to any component of the product is a contraindication (US prescribing information for Viagra and Revatio). The Viagra label cautions about the cardiac risk of sexual activity in men with existing cardiovascular disease, and it names left ventricular outflow obstruction and severely impaired autonomic control of blood pressure as conditions that can make men particularly sensitive to vasodilators. The label also states that there are no controlled data in men who had a heart attack, stroke or life-threatening arrhythmia in the last 6 months, men with resting blood pressure below 90/50 or above 170/110 mmHg, or men with heart failure or unstable angina (US prescribing information for Viagra). For eye conditions, the label calls for caution in people who have had NAION and notes that there are no controlled data in retinitis pigmentosa (US prescribing information for Viagra). Conditions that predispose to priapism are labeled cautions: penile deformities such as Peyronie's disease, sickle cell anemia, multiple myeloma and leukemia (US prescribing information for Viagra). The label states that safety in people with bleeding disorders or active peptic ulcer is unknown (US prescribing information for Viagra). Pulmonary veno-occlusive disease and sickle cell disease call for caution: the Revatio label does not recommend sildenafil in pulmonary veno-occlusive disease and reports vaso-occlusive crises in pulmonary hypertension from sickle cell disease (US prescribing information for Revatio). Two placebo-controlled trials of sildenafil in pregnancies with severe early-onset fetal growth restriction found no benefit, and one found more pulmonary hypertension in newborns (PMID: 30169244, PMID: 32585017). ### Interactions 7 pairings in our record: 3 to avoid, 2 with a caution and 2 to monitor. - Nitrates and nitric oxide donors Avoid Contraindicated: sildenafil potentiates the blood pressure lowering effect of organic nitrates, and after sildenafil a sublingual nitroglycerin tablet lowered systolic blood pressure about 4 times as much as after placebo (US prescribing information for Viagra; PMID: 10078539). - Riociguat Avoid Contraindicated: PDE5 inhibitors, sildenafil among them, may potentiate the blood pressure lowering effect of guanylate cyclase stimulators such as riociguat (US prescribing information for Viagra and Revatio). - Other PDE5 inhibitors such as tadalafil Avoid Combinations of sildenafil with other PDE5 inhibitors have not been studied and may lower blood pressure further; the Viagra label does not recommend them, and the Revatio label states that patients taking Revatio should not take Viagra or other PDE5 inhibitors (US prescribing information for Viagra and Revatio). - Alpha-blockers such as doxazosin Caution Alpha-blockers and sildenafil both lower blood pressure; in doxazosin interaction studies some men had symptomatic low blood pressure, and the label calls for caution with this combination (US prescribing information for Viagra). - Ritonavir and other CYP3A4 inhibitors Caution Ritonavir raised sildenafil exposure (AUC) 11-fold, saquinavir raised it by 210 percent and erythromycin by 182 percent (US prescribing information for Viagra). - Blood pressure medicines such as amlodipine Monitor In men with high blood pressure taking amlodipine, a single dose of sildenafil lowered supine blood pressure by a further 8 mmHg systolic and 7 mmHg diastolic (PMID: 10078539). - Bosentan and other CYP3A4 inducers Monitor Bosentan lowered sildenafil exposure (AUC) by 63 percent, and the label expects stronger CYP3A4 inducers such as rifampin to lower it further (US prescribing information for Viagra). This interaction data is compiled from published research and community reports. It may not be exhaustive. Always consult a healthcare professional before combining compounds. Need bloodwork before starting? Full hormone + metabolic panels from Anabolic Insights. Code CHONCH for first-order discount. Order Bloodwork (https://anabolicinsights.ai/?ref=nwm2zjb) 04 Dosing Free with email ## Dosing No dose on record Our record lists no dose for Sildenafil. This section holds what it does list. ### Unlock the Dosing section - Route 05 Prices ## Sildenafil prices No listings We do not track a vendor for Sildenafil yet, so this page states no price. 06 Chemistry ## Chemistry and structure Molecular formula C22H30N6O4S Molecular mass 474.6 g/mol CAS number 139755-83-2 Half-life About 4 hours for sildenafil and for its active N-desmethyl metabolite (US prescribing information for Viagra); 3.7 hours in humans in a 1999 Pfizer pharmacokinetic study (PMID: 10219969). View on PubChem (https://pubchem.ncbi.nlm.nih.gov/compound/135398744) 07 Related ## Related to Sildenafil ### In the same category - Albuterol (salbutamol)FDA Approved Albuterol, called salbutamol outside the United States, is a beta-2 adrenergic agonist and a standard asthma medicine worldwide.: https://www.bodyhackguide.co/compound/albuterol - CabergolinePhase 4 Cabergoline is a long-acting, ergot-derived dopamine D2 receptor agonist developed by Farmitalia Carlo Erba in Milan under the code FCE 21336 and approved by the FDA as Dostinex on 23 December 1996 for hyperprolactinemic disorders, either idiopathic or due to pituitary adenomas.: https://www.bodyhackguide.co/compound/cabergoline - ClascoteronePreclinical Clascoterone (brand name Winlevi; development codes CB-03-01 and, for the alopecia formulation, Breezula) is a first-in-class topical androgen receptor (AR) antagonist approved by the U.S. Food and Drug Administration in August 2020 for the treatment of acne vulgaris in patients 12 years of age and older.: https://www.bodyhackguide.co/compound/clascoterone - FinasteridePreclinical Finasteride is an orally-active selective type II 5α-reductase inhibitor that blocks the conversion of testosterone to dihydrotestosterone (DHT), the primary androgenic driver of both benign prostatic hyperplasia (BPH) and androgenetic alopecia (male-pattern hair loss).: https://www.bodyhackguide.co/compound/finasteride - GalantamineApproved drug Galantamine is an alkaloid first isolated from snowdrop plants that blocks the enzyme acetylcholinesterase, and it has been an FDA-approved prescription drug for mild to moderate dementia of the Alzheimer's type since 2001.: https://www.bodyhackguide.co/compound/galantamine - Low-Dose Naltrexone (LDN)Phase 4 on ClinicalTrials.gov Low-dose naltrexone (LDN) is naltrexone, an opioid receptor antagonist approved by the FDA for alcohol and opioid dependence, prescribed off-label at a few milligrams a day, a dose not approved for any condition (US prescribing information for naltrexone tablets and for extended-release injectable naltrexone; PMID: 42060160).: https://www.bodyhackguide.co/compound/low-dose-naltrexone All compounds (https://www.bodyhackguide.co/wiki) ### Compare Sildenafil - Alternatives to Sildenafil: https://www.bodyhackguide.co/alternatives-to/sildenafil ### Research tools - Peptide Calculator Reconstitution and syringe units: https://www.bodyhackguide.co/tools/reconstitution - Reconstitution Guide How to mix, step by step: https://www.bodyhackguide.co/guides/how-to-reconstitute-peptides - Nasal Spray Calc mL per actuation: https://www.bodyhackguide.co/tools/intranasal - Half-Life Visualizer Decay curves: https://www.bodyhackguide.co/tools/halflife All articles (https://www.bodyhackguide.co/blog) 08 Questions ## Frequently asked questions What is sildenafil? Sildenafil is a phosphodiesterase type 5 (PDE5) inhibitor developed by Pfizer and approved by the FDA as Viagra for erectile dysfunction in 1998 and as Revatio for pulmonary arterial hypertension in 2005 (Drugs@FDA NDA 020895 and NDA 021845; PMID: 16883306). Sildenafil began as a potential angina drug and was later developed for erectile dysfunction and then for pulmonary hypertension (PMID: 16883306). At recommended doses, sildenafil has no effect on erections without sexual stimulation, and sildenafil has no direct relaxing effect on isolated human penile tissue; the drug works by amplifying the nitric oxide signal released during stimulation (US prescribing information for Viagra). Are Viagra and Revatio the same drug? Viagra and Revatio both contain sildenafil citrate, with Viagra labeled for erectile dysfunction and Revatio for pulmonary arterial hypertension in adults and in children aged 1 to 17 (US prescribing information for Viagra and Revatio). The Revatio label notes that sildenafil is also marketed as Viagra and that combining Revatio with Viagra or other PDE5 inhibitors has not been studied (US prescribing information for Revatio). Sildenafil for pulmonary arterial hypertension is also approved as an intravenous injection (Drugs@FDA NDA 022473). How does sildenafil compare with tadalafil? In four head-to-head trials reviewed in a 2009 meta-analysis, sildenafil, vardenafil and tadalafil did not differ in efficacy or adverse events (PMID: 19884626). In a 2015 network meta-analysis of 82 trials, sildenafil 50 mg had the greatest efficacy among starting doses of PDE5 inhibitors and also the highest overall rate of adverse events, while tadalafil 10 mg had the lowest adverse event rate (PMID: 25817916). Sildenafil and its active metabolite have terminal half-lives of about 4 hours (US prescribing information for Viagra). Can sildenafil cause vision or hearing loss? The sildenafil labels warn that sudden vision loss from non-arteritic anterior ischemic optic neuropathy (NAION) and sudden hearing loss have been reported with PDE5 inhibitors, without a proven causal link (US prescribing information for Viagra and Revatio). In a case-crossover study, use of PDE5 inhibitors, the drug class that includes sildenafil, was associated with about twice the short-term risk of NAION (odds ratio 2.15) (PMID: 25358826). In a US survey of 11,525 men, sildenafil use was associated with self-reported hearing impairment (odds ratio 2.05), in a cross-sectional design that cannot show cause and effect (PMID: 20479381). Abnormal vision, mostly a mild, temporary color tinge but also light sensitivity or blurring, was reported in fixed-dose sildenafil trials by 11 percent of men at 100 mg against 1 percent on placebo (US prescribing information for Viagra). Why is sildenafil contraindicated with nitrates? Sildenafil and organic nitrates both raise cGMP, and sildenafil potentiates the blood pressure drop caused by nitrates (PMID: 10078539). The Viagra and Revatio labels contraindicate sildenafil with nitrates in any form, taken regularly or intermittently (US prescribing information for Viagra and Revatio). In a 1999 interaction study, a sublingual nitroglycerin tablet lowered systolic blood pressure about 4 times as much after sildenafil as after placebo (PMID: 10078539). Does sildenafil work in women? In a trial of 781 women with female sexual arousal disorder, sildenafil did not differ from placebo on any patient or partner endpoint (PMID: 12150499). Sildenafil improved the primary sexual function rating more than placebo in 98 premenopausal women with sexual dysfunction linked to serotonergic antidepressants (PMID: 18647982). The Viagra label states that Viagra is not indicated for women, and two trials of sildenafil in pregnancies with severe fetal growth restriction found no benefit, with more pulmonary hypertension in newborns in one of them (US prescribing information for Viagra; PMID: 30169244, PMID: 32585017). Does sildenafil improve exercise performance? In 10 trained men, sildenafil did not change cycling performance at sea level, while it shortened a 6-km time trial by 15 percent at a simulated altitude of 3,874 m (PMID: 16455814). In 11 volunteers, sildenafil did not improve exercise capacity in normal or low-oxygen conditions (PMID: 27414159). A study of 14 mountaineers found that sildenafil raised maximum workload in low-oxygen conditions and at Mount Everest base camp (PMID: 15289213). Related ## Articles on Sildenafil - PT-141 (Bremelanotide): Complete Research Guide Peptides, 1 July 2026: https://www.bodyhackguide.co/blog/pt-141-bremelanotide-research-guide Free 2026 Peptide Cheat Sheet (PDF) 38 compounds and blends: vial sizes, BAC water volumes, dosing ranges and bloodwork markers. Download Free (https://www.bodyhackguide.co/guides/peptide-cheat-sheet-download) BodyHackGuide (https://www.bodyhackguide.co/) Your biohacking research hub: compound pricing, brain health protocols, dosing tools, and vendor reviews. support@bodyhackguide.co Join our Discord: https://discord.gg/Mhq5UdRYBA r/BodyHackGuide on Reddit: https://reddit.com/r/BodyHackGuide **Affiliate Disclosure:** We rank every vendor on the same public, reproducible methodology (https://www.bodyhackguide.co/vendors/methodology). 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In a 1998 trial in men with erectile dysfunction, 69 percent of attempts at intercourse succeeded on sildenafil against 22 percent on placebo, and in a 278-person trial in pulmonary arterial hypertension sildenafil raised six-minute walk distance by 45 to 50 meters more than placebo (PMID: 9580646, PMID: 16291984). Sildenafil missed its primary endpoints in trials of heart failure with preserved ejection fraction and of severe fetal growth restriction, and a Dutch trial in pregnancy was halted after more newborns in the sildenafil group developed pulmonary hypertension (PMID: 23478662, PMID: 30169244, PMID: 32585017). The US labels contraindicate sildenafil with nitrates and with the guanylate cyclase stimulator riociguat, and they warn about low blood pressure, priapism, sudden vision loss and sudden hearing loss (US prescribing information for Viagra and Revatio).", "activeIngredient": "Sildenafil", "administrationRoute": "Oral, Intravenous", "mechanismOfAction": "How PDE5 inhibition works During sexual stimulation, nitric oxide released in the corpus cavernosum activates the enzyme guanylate cyclase, which raises cyclic guanosine monophosphate (cGMP) and relaxes smooth muscle so that blood flows into the penis (US prescribing information for Viagra). Sildenafil blocks phosphodiesterase type 5 (PDE5), the enzyme that breaks down cGMP in this tissue, so sildenafil amplifies the nitric oxide signal; the label states that sildenafil has no direct relaxing effect on isolated human corpus cavernosum and, at recommended doses, no effect without sexual stimulation (US prescribing information for Viagra). Organic nitrates also act by raising cGMP, and sildenafil potentiates their blood pressure lowering effect (PMID: 10078539; US prescribing information for Viagra). In laboratory tests at Pfizer, sildenafil inhibited PDE5 from human penile tissue with a 50 percent inhibitory concentration (IC50) of 3.5 nanomolar, was 80 to more than 8,500 times weaker against PDE1 to PDE4, and was only about 9 times weaker against PDE6, the light-sensing enzyme of the retina, which in this study came from cow retina rather than human tissue (PMID: 9598563). The label states that this lower selectivity is thought to be the basis of the changes in color vision some users report (US prescribing information for Viagra). The lung and other tissues PDE5 is also found in platelets, vascular and visceral smooth muscle, skeletal muscle, lung, heart, brain, prostate and other tissues (US prescribing information for Viagra). In the lung, cGMP signaling relaxes vascular smooth muscle and slows its growth, the rationale given for testing sildenafil in pulmonary arterial hypertension (PMID: 16291984). In 14 healthy mountaineers, sildenafil lowered pulmonary artery pressure at rest and during exercise while they breathed low-oxygen air and again at Mount Everest base camp (PMID: 15289213). Absorption, breakdown and duration The absolute oral bioavailability of sildenafil was 41 percent in healthy men, in whom food delayed peak levels by about an hour and lowered the peak concentration by 29 percent (PMID: 11879254). Sildenafil is cleared mainly by the liver enzyme CYP3A4, with CYP2C9 as a minor route, and its main circulating metabolite, N-desmethyl sildenafil, has about half the PDE5 potency of the parent drug and accounts for about 20 percent of its effect (US prescribing information for Viagra). In a 1999 Pfizer study, the elimination half-life in humans was 3.7 hours, and no unchanged drug was detected in human excreta (PMID: 10219969). In two crossover studies in men with erectile dysfunction, erections began a median of 27 minutes after a 50 mg dose, and the authors reported a duration of action of at least 4 hours (PMID: 11879261).", "legalStatus": "Approved (prescription)" } }, { "@context": "https://schema.org", "@type": "FAQPage", "mainEntity": [ { "@type": "Question", "name": "What is sildenafil?", "acceptedAnswer": { "@type": "Answer", "text": "Sildenafil is a phosphodiesterase type 5 (PDE5) inhibitor developed by Pfizer and approved by the FDA as Viagra for erectile dysfunction in 1998 and as Revatio for pulmonary arterial hypertension in 2005 (Drugs@FDA NDA 020895 and NDA 021845; PMID: 16883306). Sildenafil began as a potential angina drug and was later developed for erectile dysfunction and then for pulmonary hypertension (PMID: 16883306). At recommended doses, sildenafil has no effect on erections without sexual stimulation, and sildenafil has no direct relaxing effect on isolated human penile tissue; the drug works by amplifying the nitric oxide signal released during stimulation (US prescribing information for Viagra)." } }, { "@type": "Question", "name": "Are Viagra and Revatio the same drug?", "acceptedAnswer": { "@type": "Answer", "text": "Viagra and Revatio both contain sildenafil citrate, with Viagra labeled for erectile dysfunction and Revatio for pulmonary arterial hypertension in adults and in children aged 1 to 17 (US prescribing information for Viagra and Revatio). The Revatio label notes that sildenafil is also marketed as Viagra and that combining Revatio with Viagra or other PDE5 inhibitors has not been studied (US prescribing information for Revatio). Sildenafil for pulmonary arterial hypertension is also approved as an intravenous injection (Drugs@FDA NDA 022473)." } }, { "@type": "Question", "name": "How does sildenafil compare with tadalafil?", "acceptedAnswer": { "@type": "Answer", "text": "In four head-to-head trials reviewed in a 2009 meta-analysis, sildenafil, vardenafil and tadalafil did not differ in efficacy or adverse events (PMID: 19884626). In a 2015 network meta-analysis of 82 trials, sildenafil 50 mg had the greatest efficacy among starting doses of PDE5 inhibitors and also the highest overall rate of adverse events, while tadalafil 10 mg had the lowest adverse event rate (PMID: 25817916). Sildenafil and its active metabolite have terminal half-lives of about 4 hours (US prescribing information for Viagra)." } }, { "@type": "Question", "name": "Can sildenafil cause vision or hearing loss?", "acceptedAnswer": { "@type": "Answer", "text": "The sildenafil labels warn that sudden vision loss from non-arteritic anterior ischemic optic neuropathy (NAION) and sudden hearing loss have been reported with PDE5 inhibitors, without a proven causal link (US prescribing information for Viagra and Revatio). In a case-crossover study, use of PDE5 inhibitors, the drug class that includes sildenafil, was associated with about twice the short-term risk of NAION (odds ratio 2.15) (PMID: 25358826). In a US survey of 11,525 men, sildenafil use was associated with self-reported hearing impairment (odds ratio 2.05), in a cross-sectional design that cannot show cause and effect (PMID: 20479381). Abnormal vision, mostly a mild, temporary color tinge but also light sensitivity or blurring, was reported in fixed-dose sildenafil trials by 11 percent of men at 100 mg against 1 percent on placebo (US prescribing information for Viagra)." } }, { "@type": "Question", "name": "Why is sildenafil contraindicated with nitrates?", "acceptedAnswer": { "@type": "Answer", "text": "Sildenafil and organic nitrates both raise cGMP, and sildenafil potentiates the blood pressure drop caused by nitrates (PMID: 10078539). The Viagra and Revatio labels contraindicate sildenafil with nitrates in any form, taken regularly or intermittently (US prescribing information for Viagra and Revatio). In a 1999 interaction study, a sublingual nitroglycerin tablet lowered systolic blood pressure about 4 times as much after sildenafil as after placebo (PMID: 10078539)." } }, { "@type": "Question", "name": "Does sildenafil work in women?", "acceptedAnswer": { "@type": "Answer", "text": "In a trial of 781 women with female sexual arousal disorder, sildenafil did not differ from placebo on any patient or partner endpoint (PMID: 12150499). Sildenafil improved the primary sexual function rating more than placebo in 98 premenopausal women with sexual dysfunction linked to serotonergic antidepressants (PMID: 18647982). The Viagra label states that Viagra is not indicated for women, and two trials of sildenafil in pregnancies with severe fetal growth restriction found no benefit, with more pulmonary hypertension in newborns in one of them (US prescribing information for Viagra; PMID: 30169244, PMID: 32585017)." } }, { "@type": "Question", "name": "Does sildenafil improve exercise performance?", "acceptedAnswer": { "@type": "Answer", "text": "In 10 trained men, sildenafil did not change cycling performance at sea level, while it shortened a 6-km time trial by 15 percent at a simulated altitude of 3,874 m (PMID: 16455814). In 11 volunteers, sildenafil did not improve exercise capacity in normal or low-oxygen conditions (PMID: 27414159). A study of 14 mountaineers found that sildenafil raised maximum workload in low-oxygen conditions and at Mount Everest base camp (PMID: 15289213)." } } ] }, { "@context": "https://schema.org", "@type": "Organization", "@id": "https://www.bodyhackguide.co#organization", "name": "BodyHackGuide", "alternateName": "BHG", "url": "https://www.bodyhackguide.co", "logo": { "@type": "ImageObject", "url": "https://www.bodyhackguide.co/logo.png", "width": 512, "height": 512 }, "description": "Evidence-based research reference for peptides and nootropics. 273 compound profiles, interactive dosing calculators, vendor price comparisons, and trust-scored vendor reviews scored on a public, reproducible methodology applied to every vendor. 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