Sildenafil Side Effects

Reported Sildenafil side effects

Common effects in trials In fixed-dose erectile dysfunction trials, headache affected 16, 21 and 28 percent of men on 25, 50 and 100 mg against 7 percent on placebo, and flushing (10 to 19 percent against 2 percent), indigestion or dyspepsia (3 to 17 percent against 2 percent) and abnormal vision (1 to 11 percent against 1 percent) were also more common than with placebo (US prescribing information for Viagra). The abnormal vision was mostly a mild, temporary color tinge, sensitivity to light or blurring, and 2.5 percent of men on sildenafil against 2.3 percent on placebo stopped treatment because of adverse reactions (US prescribing information for Viagra). A 2009 meta-analysis of 49 randomized trials found more adverse events of any kind with sildenafil than with placebo (risk ratio 1.56) but no difference in serious adverse events or withdrawals, and it noted a lack of trials reporting harms beyond 6 months (PMID: 19592078). Blood pressure and the heart In healthy volunteers, sildenafil caused transient decreases in supine blood pressure, by a mean maximum of 8.4/5.5 mmHg, and the label states that treatments for erectile dysfunction, sildenafil among them, should not generally be used in men for whom sexual activity is inadvisable because of their cardiovascular status (US prescribing information for Viagra). When men took sildenafil before a sublingual nitroglycerin tablet, systolic blood pressure fell about 4 times as much as after placebo (PMID: 10078539). In pooled data from more than 120 trials run from 1993 to 2001, the rate of heart attack or cardiovascular death was 0.91 per 100 person-years on sildenafil and 0.84 on placebo (relative risk 1.08, 95% CI 0.45 to 2.77) (PMID: 14529061). After approval, heart attacks, sudden cardiac death, strokes and other serious cardiovascular events were reported in temporal association with Viagra, mostly in men with existing cardiovascular risk factors, and the label states that it is not possible to determine whether these events were caused by the drug, by sexual activity, by underlying disease or by other factors (US prescribing information for Viagra). In a Swedish registry study of men with coronary disease taking nitrates, combined use of a PDE5 inhibitor (5,710 men) was associated with higher all-cause mortality (hazard ratio 1.39) and with more heart attacks and heart failure; the study was observational (PMID: 38233015). Sudden vision loss (NAION) The label states that non-arteritic anterior ischemic optic neuropathy (NAION), a cause of decreased vision including permanent loss of vision, has been reported rarely after marketing with all PDE5 inhibitors, and that its background rate is 2.5 to 11.8 cases per 100,000 men aged 50 or older each year (US prescribing information for Viagra). A case-crossover study with Pfizer authors found about twice the risk of NAION within five half-lives of a PDE5 inhibitor dose among 43 confirmed cases (odds ratio 2.15, 95% CI 1.06 to 4.34), which the authors estimated as three added cases per 100,000 men aged 50 or older each year with weekly use (PMID: 25358826). A similar study with Eli Lilly authors found a rate ratio of 2.27 (95% CI 0.99 to 5.20) over 30 days, and a 2018 meta-analysis found no significant overall association but a significant one in the sildenafil subgroup (risk ratio 2.25) (PMID: 28336289, PMID: 29884471). Hearing loss Sudden decrease or loss of hearing, sometimes with ringing in the ears and dizziness, has been reported in temporal association with PDE5 inhibitors, and the label states that it is not possible to determine whether these events are related directly to the drugs (US prescribing information for Viagra). In a cross-sectional US survey of 11,525 men aged 40 or older, self-reported hearing impairment was associated with sildenafil use (odds ratio 2.05) but not with tadalafil or vardenafil use (PMID: 20479381). Priapism Erections lasting more than 4 hours and priapism, defined in the label as a painful erection lasting more than 6 hours, have been reported infrequently since approval, and the label warns that untreated priapism can cause penile tissue damage and permanent loss of potency (US prescribing information for Viagra). Melanoma In the Health Professionals Follow-up Study of 25,848 US men, recent sildenafil use was associated with a higher risk of melanoma (hazard ratio 1.84, 95% CI 1.04 to 3.22) (PMID: 24710960). A Swedish study of 4,065 melanoma cases found a smaller association with PDE5 inhibitors (odds ratio 1.21) that was seen with a single prescription but not with repeated prescriptions and only for early-stage tumors, a pattern the authors said raises questions about whether the link is causal (PMID: 26103029). A 2017 meta-analysis of five observational studies found a slightly higher melanoma risk with PDE5 inhibitor use (odds ratio 1.12) (PMID: 28728871). Pregnancy and fetal growth restriction The Viagra label states that the drug is not indicated for women and reports no adverse developmental outcomes in rats and rabbits given sildenafil during organogenesis (US prescribing information for Viagra). In a Dutch trial of 216 pregnant women with severe early-onset fetal growth restriction, pulmonary hypertension occurred in 18.8 percent of newborns in the sildenafil group against 5.1 percent with placebo (relative risk 3.67), and the trial was stopped early for safety concerns on 19 July 2018 (PMID: 32585017). Children with pulmonary arterial hypertension In the long-term extension of a pediatric trial, children randomized to the high dose had higher mortality than those on the low dose (hazard ratio 3.95, 95% CI 1.46 to 10.65), though the authors noted that multiple analyses raised uncertainty about the dose and survival relationship (PMID: 24637559). The Revatio label reports deaths in 9.1, 13.5 and 22 percent of the low, medium and high dose groups of the pediatric studies, and states that a causal link is unlikely in view of a later adult study (US prescribing information for Revatio; PMID: 38752352). Other labeled warnings The labels also report nosebleeds in 13 percent of Revatio-treated patients with pulmonary arterial hypertension linked to connective tissue disease, more vaso-occlusive crises with sildenafil in a small, prematurely stopped study of pulmonary hypertension from sickle cell disease, a risk of pulmonary edema in pulmonary veno-occlusive disease, seizures and transient global amnesia after marketing, and hypersensitivity reactions including anaphylaxis (US prescribing information for Viagra and Revatio).

When to continue, reduce, or stop Sildenafil

Sildenafil 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). 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).

Why vendor quality drives Sildenafil side-effect frequency

Research-compound communities consistently report that adverse-event frequency tracks with source quality. Three reasons: (1) impurity profiles vary by lab (residual synthesis byproducts can trigger reactions); (2) mislabeled mass means actual dose can be 50-150% of stated dose; (3) reconstitution-grade water and capping methodology affect long-term storage stability. COA-verified vendors with published HPLC data minimize all three failure modes. Check a vendor's COA record and Trust Score before you buy.

Sildenafil side effects FAQ

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