Sildenafil

Phosphodiesterase type 5 inhibitors (PDE5)

ATC code: G04BE03

Brand names: Viagra, Revatio

Updated 19 Jun 2026 · Methodology

Indications

Erectile dysfunction

First line

First-line for erectile dysfunction per AUA 2018 and EAU 2024. Standard dose 50 mg taken 30–60 minutes before intercourse; titrate up to 100 mg or down to 25 mg. Not more than once daily. Effect lasts up to 4 hours and requires sexual stimulation. In diabetes, post-prostatectomy, or on antihypertensives – usually maximum dose is needed.

Sources

ICD-10: N52.9 · ICD-11: HA01.1

Pulmonary arterial hypertension

First line

Per /ERS 2022, sildenafil is first-line for group 1 pulmonary arterial hypertension in functional class I–III. Dose 20 mg three times daily. Use in specialized centers with confirmed diagnosis and right heart catheterization.

As Revatio 20 mg three times daily.

Sources

ICD-10: I27.0 · ICD-11: BB01.0

Marketing claims without evidence base

The drug is promoted for these uses outside international guidelines. Each entry below is analyzed against AEMPS, FDA, EMA, Cochrane and major RCTs.

Anti-aging and longevity

Not recommended

Sildenafil is a phosphodiesterase-5 (PDE5) inhibitor. It is prescribed for erectile dysfunction and pulmonary arterial hypertension (AEMPS Ficha Técnica). In anti-aging communities, sildenafil and other PDE5 inhibitors are promoted as rejuvenating, improving cerebral and vascular blood flow, and boosting endurance. In people without erectile dysfunction or pulmonary hypertension, no clinical studies of prophylactic use exist; cerebral blood flow improvement and life extension via PDE5 inhibitors have not been demonstrated. The drug causes headache, facial flushing, nasal congestion, dyspepsia, visual disturbances (bluish tint), and rarely non-arteritic anterior ischemic optic neuropathy (risk of permanent vision loss). It is dangerous combined with nitrates (sharp blood pressure drop, shock risk). If sildenafil is being taken for anti-aging, consider seeking a second opinion.

Sources

Athletic endurance

Not recommended

Sildenafil is marketed for athletic performance and endurance in healthy athletes – particularly during hypoxic or high-altitude training – via systemic vasodilation and improved pulmonary blood flow. WADA has considered PDE5 inhibitors for the Prohibited List since 2009; as of 2026 they are not on the list. ACSM and IOC Medical Commission do not describe clinical indications for sildenafil in healthy athletes – the evidence base for improving general or anaerobic performance in healthy people is absent.

Sources

How to read tiers A–F

AStrong evidence – first or second line in international guidelines
BRecommended in selected cases
CStudy data contradict each other
DBenefit not proven, no documented harm
FDocumented harm, or risk without benefit

Mechanism of action

Selective reversible phosphodiesterase type 5 (PDE5) inhibitor. Blocks cGMP breakdown in penile cavernosal smooth muscle during sexual stimulation, producing smooth muscle relaxation and erection. No effect without sexual stimulation — not an «aphrodisiac». Half-life 4 hours, onset 30–60 minutes. Fatty meals delay onset.

Safety

Contraindications

Concurrent nitrates (nitroglycerin, isosorbide dinitrate, amyl nitrite)
Concurrent soluble guanylate cyclase stimulators (riociguat)
Severe cardiovascular disease in which sexual activity is contraindicated
Severe hepatic impairment
Severe hypotension (SBP below 90)
Recent stroke or MI
Known severe retinal disease (hereditary pigmentary degenerations)
Hypersensitivity

Serious adverse effects

Priapism (erection over 4 hours requiring urgent care)
Non-arteritic anterior ischemic optic neuropathy (NAION) — rare but irreversible vision loss
Sudden sensorineural hearing loss (rare)
Severe hypotension with nitrates
Cardiovascular events in severe CAD

Common adverse effects

Headache (10–20 %)
Flushing
Dyspepsia
Nasal congestion
Visual disturbances (blue tinge, photophobia, color perception changes)
Back pain
Dizziness

Pregnancy: can you take Sildenafil?

FDA categories were retired in 2015. Not indicated in women for ED. In pregnant patients with PAH, sildenafil is used on strict indication with pulmonologist and cardiologist input.

Breastfeeding: can you take Sildenafil?

Not indicated in women for ED. In PAH patients, breastfeeding compatibility is assessed individually.

Calculate RID Full profile on NIH LactMed ↗

Reference information, not a clinical decision. Discuss feeding pauses or changes with your physician or an IBCLC.

Practical notes

Timing and administration

Take 30–60 minutes before planned intercourse, no more than once daily. Fatty meals delay onset by 1–2 hours — take on an empty stomach or after a light meal. Alcohol is not contraindicated but increases hypotension risk. In elderly or severe renal/hepatic impairment — start 25 mg.

Special situations

Concomitant nitrates (nitroglycerin, isosorbide dinitrate, amyl nitrite) and soluble guanylate cyclase stimulators (riociguat) are absolutely contraindicated — risk of severe, even fatal hypotension. Patients on nitrate therapy do not receive PDE5 inhibitors; patients on PDE5 inhibitors who need nitrates for ACS require at least 24 hours after the last sildenafil dose (48 hours for tadalafil). Concurrent α-blockers (tamsulosin, doxazosin) in BPH — orthostatic hypotension risk, separate dosing times.

Common myths

Myth: 'Viagra causes erection in any man'. Fact: PDE5 inhibitors require sexual stimulation — no stimulation, no effect. They are not aphrodisiacs.

Myth: 'Viagra triggers heart attacks'. Fact: in patients without severe CAD and not on nitrates, PDE5 inhibitors are safe. Sexual activity itself does not 'trigger' MI in stable patients.

Myth: 'Viagra prolongs intercourse'. Fact: it is for erectile dysfunction, not duration enhancement or for patients without erectile issues. Use for those purposes risks side effects without benefit.

Drug–nutrient interactions

Grapefruit juice

Grapefruit juice weakly inhibits CYP3A4 in the gut wall and, according to the Viagra SmPC, can cause small rises in sildenafil levels. The interaction is minor: at most, headache, flushing, nasal congestion and a drop in blood pressure become more noticeable. The SmPC does not ask patients to avoid grapefruit.

Source: EMA: Ficha técnica de Viagra 50 mg comprimidos recubiertos con película (sildenafilo) (2025)

Drug–drug interactions

12 pairs found. Sorted from critical to minor.

CriticalIsosorbide dinitrateOrganic nitrate, nitric oxide donor

Mechanism

Sildenafil and isosorbide dinitrate via cGMP – synergistic hypotension.

Symptoms

Fatal hypotension.

Management

Combination contraindicated.

Sources

Pair details →Isosorbide dinitrate →

CriticalIsosorbide mononitrateLong-acting organic nitrate

Mechanism

Sildenafil inhibits PDE-5; isosorbide mononitrate releases nitric oxide. Both pathways converge on cGMP accumulation in vascular smooth muscle, causing severe systemic vasodilation. Blood pressure drops to shock levels with risk of myocardial infarction and stroke. contraindicates PDE-5 inhibitors with any nitrate.

Symptoms

Sudden hypotension within an hour: dizziness, syncope, tachycardia, pallor, loss of consciousness. Cardiac arrest possible.

Management

Combination contraindicated. Allow at least 24 hours between the last sildenafil dose and any nitrate (48 hours for tadalafil). A patient with angina who has taken sildenafil should not receive nitrates – use morphine, oxygen and urgent angiography.

Sources

Pair details →Isosorbide mononitrate →

CriticalNitroglycerinOrganic nitrate

Mechanism

Sildenafil blocks phosphodiesterase-5, slowing breakdown of cGMP – the intracellular mediator of vascular relaxation. Nitroglycerin raises cGMP production. Co-administration sharply amplifies vasodilation – severe systemic hypotension develops. Fatal cases have been reported.

Symptoms

Sudden drop in blood pressure: dizziness, visual greying, syncope, shock. In ischaemic heart disease, risk of myocardial infarction from coronary perfusion collapse.

Management

The combination is not prescribed. After sildenafil, nitrates are permitted only after 24 hours. After tadalafil (long-acting), only after 48 hours. In acute coronary syndrome after recent sildenafil, replace nitrates with morphine and oxygen; for preload reduction, use furosemide.

Sources

Pair details →Nitroglycerin →

CriticalRiociguatSoluble guanylate cyclase (sGC) stimulator

Mechanism

Both activate cGMP pathway. Synergistic hypotension. Adempas Section 4.3 strict contraindication.

Symptoms

Severe hypotension.

Management

Combination contraindicated.

Sources

Pair details →Riociguat →

MajorAmiodaroneClass III antiarrhythmics (Vaughan Williams)

Mechanism

Dual mechanism: amiodarone blocks CYP3A4 – a partial sildenafil metabolic route – and both drugs prolong QT. Sildenafil plasma levels rise 2- to 4-fold.

Symptoms

Sudden blood pressure drop: dizziness, syncope. QT prolongation on ECG with torsades de pointes risk. Visual disturbances.

Management

On amiodarone, cap sildenafil at 25 mg (instead of 50–100 mg) and limit to one dose every 48 hours. ECG before start and at 2 weeks; maintain potassium and magnesium.

Sources

Pair details →Amiodarone →

MajorClarithromycinMacrolide antibiotic

Mechanism

Sildenafil is cleared mainly through CYP3A4 (sildenafil SmPC). The European Medicines Agency () places clarithromycin among the more potent inhibitors of this enzyme and assumes about a 7-fold increase in sildenafil exposure with it (sildenafil SmPC for pulmonary hypertension, EMA). The US Food and Drug Administration () warns that low blood pressure, fainting and prolonged erection may occur at higher sildenafil exposure (sildenafil FDA label).

Symptoms

Sudden blood pressure drop: dizziness, syncope. Priapism – painful erection lasting more than 4 hours, requiring emergency care. Worsening of visual disturbances (cyanopsia) and tinnitus.

Management

Avoid the combination: the US Food and Drug Administration () does not recommend sildenafil together with clarithromycin (clarithromycin FDA label), and for pulmonary arterial hypertension it does not recommend sildenafil with any strong CYP3A4 inhibitor (sildenafil FDA label for pulmonary hypertension). If sildenafil for pulmonary hypertension is still needed during a clarithromycin course, the European Medicines Agency () recommends reducing the dose to 20 mg once daily (sildenafil SmPC for pulmonary hypertension, EMA). For erectile dysfunction, consider a 25 mg starting dose in patients taking CYP3A4 inhibitors (sildenafil SmPC, EMA; sildenafil FDA label), with no more than one dose per day (sildenafil SmPC, EMA). The clarithromycin SmPC also advises considering a lower sildenafil dose (clarithromycin SmPC). Tell the patient to seek urgent medical help if an erection lasts longer than 4 hours (sildenafil SmPC, EMA).

Sources

Pair details →Clarithromycin →

MajorClonidineCentral α2-adrenergic agonist

Mechanism

Additive hypotensive effect. Sildenafil vasodilates by blocking phosphodiesterase-5; clonidine lowers blood pressure via central α2-agonism. Combined action can cause symptomatic hypotension.

Symptoms

Sudden blood pressure drop: postural dizziness, syncope. Particularly dangerous in older patients and in ischaemic heart disease.

Management

The combination is acceptable in stable hypertension. Cap sildenafil at 25 mg (instead of 50–100 mg). Warn the patient about orthostatic hypotension; take the first dose lying down.

Sources

FDA: Viagra section 7 (2014)

Pair details →Clonidine →

MajorKetoconazoleSystemic antimycotics. Imidazole derivatives

Mechanism

Ketoconazole strongly blocks CYP3A4 – the main sildenafil metabolic route. Sildenafil plasma levels rise 4- to 8-fold. The hypotensive effect surges; priapism and ischaemic optic neuropathy risks rise.

Symptoms

Sudden blood pressure drop: dizziness, syncope. Priapism – painful erection lasting more than 4 hours. Visual disturbances, tinnitus. Symptoms appear within hours of co-administration.

Management

Avoid the combination. Alternative antifungals: terbinafine for dermatophytosis or echinocandins for systemic mycoses. If ketoconazole is needed, cap sildenafil at 25 mg and one dose per 24 hours.

Sources

Pair details →Ketoconazole →

MajorRitonavirHIV protease inhibitor / pharmacokinetic booster

Mechanism

Sildenafil is broken down in the liver by CYP3A4, and ritonavir strongly inhibits this enzyme. With ritonavir 500 mg twice daily, sildenafil area under the curve (AUC) rose 11-fold and peak concentration 4-fold; 24 hours after the dose, sildenafil levels were still about 200 ng/mL compared with about 5 ng/mL without ritonavir. This raises the risk of sildenafil side effects.

Symptoms

A sharp drop in blood pressure with dizziness and fainting, prolonged erection, visual disturbances. An erection lasting more than 4 hours needs urgent medical care.

Management

The European Medicines Agency () contraindicates the combination in pulmonary arterial hypertension (ritonavir label and pulmonary hypertension sildenafil label, EMA). During a nirmatrelvir/ritonavir course for COVID-19, sildenafil is contraindicated for any indication (nirmatrelvir/ritonavir label, EMA). For erectile dysfunction in a patient on long-term ritonavir, the combination is not recommended (sildenafil label). If sildenafil is still needed, use a single 25 mg dose and no more than 25 mg in 48 hours (ritonavir and sildenafil labels). The US Food and Drug Administration () sets the same limit and advises closer monitoring for side effects: low blood pressure, fainting, prolonged erection (ritonavir and sildenafil FDA labels).

Sources

Pair details →Ritonavir →

ModerateAmlodipineCalcium channel blockers (dihydropyridines)

Mechanism

Additive hypotension via different mechanisms – calcium channel blockade (amlodipine) + PDE5 blockade (sildenafil). Clinically significant in patients with prior hypotension.

Symptoms

Lower blood pressure, postural dizziness, fatigue. Older patients: fall risk.

Management

The combination is acceptable in stable hypertension. Take the first sildenafil dose lying down; do not exceed 25–50 mg. Warn the patient about orthostatic hypotension.

Sources

Pair details →Amlodipine →

ModerateBisoprololSelective beta-adrenergic blockers

Mechanism

Sildenafil is a vasodilator via PDE5 blockade. Combined with bisoprolol: risk of symptomatic hypotension, especially with the first dose.

Symptoms

Lower blood pressure, postural dizziness, fatigue. Older patients: fall risk.

Management

The combination is acceptable in stable hypertension with a well-titrated beta-blocker. Take the first sildenafil dose lying down; do not exceed 25–50 mg. Warn the patient about orthostatic hypotension.

Sources

FDA: Bisoprolol tablet (Micro Labs Limited) – Prescribing Information (2016)

Pair details →Bisoprolol →

ModerateLosartanAngiotensin II receptor blockers (sartans)

Mechanism

Both lower blood pressure by different routes: losartan blocks the angiotensin II receptor, sildenafil relaxes vascular smooth muscle through the nitric oxide/cGMP pathway. The effect is additive and quantified in the label for a comparable antihypertensive: with amlodipine, sildenafil 100 mg lowered supine systolic pressure by a further 8 mmHg and diastolic by 7 mmHg.

Symptoms

Dizziness on standing, vision darkening for a few seconds, facial flushing, headache, palpitations. In older or dehydrated people the drop can reach syncope. The nitrate combination is contraindicated and should not be confused with this one.

Management

The pair is acceptable with controlled blood pressure. Start at the lowest sildenafil dose, avoid alcohol, and stand up slowly for the first hours. Skip it on the day the antihypertensive dose is adjusted or a diuretic is added, and always check for nitrates, where the combination is no longer possible.

Sources

Pair details →Losartan →

Label mentions63 mentions

Verbatim lines from the interaction sections, in the language of the label

From this drug’s label

Criticalnitratesclass named in the label
«Nitrates: Consistent with its known effects on the nitric oxide/cGMP pathway [ see Clinical Pharmacology ( 12.1 , 12.2)] , sildenafil tablets were shown to potentiate the hypotensive effects of…»
FDA, section 4 · Open on DailyMed
Criticalnitratosclass named in the label
«De acuerdo con sus conocidos efectos sobre la vía óxido nítrico/guanosina monofosfato cíclica (GMPc) (ver sección 5.1), sildenafilo ha demostrado potenciar los efectos hipotensores de los nitratos…»
AEMPS, section 4.3 · Open on CIMA
CriticalRiociguat
«La administración conjunta de inhibidores de la PDE5, incluyendo sildenafilo, con estimuladores de la guanilato-ciclasa, como riociguat, está contraindicado ya que puede producir hipotensión…»
AEMPS, section 4.3 · Open on CIMA
CriticalRiociguat
«Concomitant Guanylate Cyclase (GC) Stimulators: Do not use sildenafil tablets in patients who are using a GC stimulator, such as riociguat. PDE5 inhibitors, including sildenafil tablets, may…»
FDA, section 4 · Open on DailyMed
MajorCYP3A4 inhibitorsclass named in the label
«DRUG INTERACTIONS: • Sildenafil tablets can potentiate the hypotensive effects of nitrates, alpha blockers, and anti-hypertensives ( 4.1 , 5.5 , 7.1 , 7.2 , 7.3 , 12.2 ) • With concomitant use of…»
FDA, section 7 · Open on DailyMed
MajorErythromycin
«DRUG INTERACTIONS: • Sildenafil tablets can potentiate the hypotensive effects of nitrates, alpha blockers, and anti-hypertensives ( 4.1 , 5.5 , 7.1 , 7.2 , 7.3 , 12.2 ) • With concomitant use of…»
FDA, section 7 · Open on DailyMed
MajorItraconazole
«DRUG INTERACTIONS: • Sildenafil tablets can potentiate the hypotensive effects of nitrates, alpha blockers, and anti-hypertensives ( 4.1 , 5.5 , 7.1 , 7.2 , 7.3 , 12.2 ) • With concomitant use of…»
FDA, section 7 · Open on DailyMed
MajorKetoconazole
«DRUG INTERACTIONS: • Sildenafil tablets can potentiate the hypotensive effects of nitrates, alpha blockers, and anti-hypertensives ( 4.1 , 5.5 , 7.1 , 7.2 , 7.3 , 12.2 ) • With concomitant use of…»
FDA, section 7 · Open on DailyMed
MajorRitonavir
«La administración conjunta de ritonavir, inhibidor de la proteasa del VIH, el cual presenta una potente acción inhibitoria sobre el citocromo P450, en el estado estacionario (500 mg dos veces al día)…»
AEMPS, section 4.5 · Open on CIMA
MajorRitonavir
«DRUG INTERACTIONS: • Sildenafil tablets can potentiate the hypotensive effects of nitrates, alpha blockers, and anti-hypertensives ( 4.1 , 5.5 , 7.1 , 7.2 , 7.3 , 12.2 ) • With concomitant use of…»
FDA, section 7 · Open on DailyMed
ModerateKetoconazole
«El análisis de los datos farmacocinéticos de los ensayos clínicos, mostró que se produjo una reducción del aclaramiento de sildenafilo cuando se administró concomitantemente con inhibidores del…»
AEMPS, section 4.5 · Open on CIMA
MinorAmlodipine
«diuréticos, beta bloqueantes, inhibidores de la ECA, antagonistas de la angiotensina II, fármacos antihipertensivos (vasodilatadores y de acción central), bloqueantes de las neuronas adrenérgicas…»
AEMPS, section 4.5 · Open on CIMA
Acetylsalicylic acid
«Sildenafilo (50 mg) no potenció el aumento del tiempo de hemorragia causado por ácido acetilsalicílico (150 mg).»
AEMPS, section 4.5 · Open on CIMA
Amlodipine
«Amlodipine: When sildenafil tablets 100 mg were co-administered with amlodipine (5 mg or 10 mg) to hypertensive patients, the mean additional reduction on supine blood pressure was 8 mmHg systolic…»
FDA, section 7 · Open on DailyMed
antagonistas del calcioclass named in the label
«Aunque no se han realizado estudios de interacción específica con todos los fármacos posibles, el análisis de los datos farmacocinéticos no mostró efecto alguno sobre la farmacocinética de…»
AEMPS, section 4.5 · Open on CIMA
antiácidosclass named in the label
«Dosis únicas de antiácido (hidróxido magnésico/hidróxido de aluminio) no afectaron la biodisponibilidad de sildenafilo.»
AEMPS, section 4.5 · Open on CIMA
antidepresivos tricíclicosclass named in the label
«Aunque no se han realizado estudios de interacción específica con todos los fármacos posibles, el análisis de los datos farmacocinéticos no mostró efecto alguno sobre la farmacocinética de…»
AEMPS, section 4.5 · Open on CIMA
Azithromycin
«Cuando se administró una dosis única de 100 mg de sildenafilo con eritromicina, un inhibidor específico del CYP3A4, hubo un incremento del 182% en la exposición sistémica de sildenafilo (AUC) cuando…»
AEMPS, section 4.5 · Open on CIMA

From other drugs’ labels

CriticalCobicistat
«CONTRAINDICATIONS: Phosphodiesterase-5 (PDE-5) Inhibitor: sildenafil when administered as Revatio ® for the treatment of pulmonary arterial hypertension»
FDA, section 4 · Open on DailyMed
CriticalDarunavir
«CONTRAINDICATIONS: • Alpha 1-adrenoreceptor antagonist: alfuzosin • Anti-gout: colchicine, in patients with renal and/or hepatic impairment • Antimycobacterial: rifampin • Antipsychotics: lurasidone…»
FDA, section 4 · Open on DailyMed
CriticalIsosorbide dinitrate
«CONTRAINDICATIONS: Do not use isosorbide dinitrate in patients who are taking certain drugs for erectile dysfunction (phosphodiesterase inhibitors), such as sildenafil, tadalafil, or vardenafil…»
FDA, section 4 · Open on DailyMed
CriticalIsosorbide mononitrate
«Los pacientes en tratamiento con este preparado no deben recibir la administración concomitante de inhibidores de la 5-fosfodiesterasa como el sildenafilo para la disfunción eréctil (véase sección…»
AEMPS, section 4.3 · Open on CIMA
CriticalIsosorbide mononitrate
«CONTRAINDICATIONS: Do not use isosorbide mononitrate in patients who are taking certain drugs for erectile dysfunction (phosphodiesterase inhibitors), such as sildenafil, tadalafil, or vardenafil…»
FDA, section 4 · Open on DailyMed
CriticalNitroglycerin
«Uso concomitante de inhibidores de la fosfodiesterasa tipo 5 (PDE5), como el sildenafilo, tadalafilo, vardenafilo,ya que pueden potenciar el efecto vasodilatador de Cordiplast, provocando una…»
AEMPS, section 4.3 · Open on CIMA
CriticalNitroglycerin
«CONTRAINDICATIONS: Use of phosphodiesterase type 5 (PDE-5) inhibitors, such as avanafil, sildenafil, tadalafil, or vardenafil, or soluble guanylate cyclase (sGC) stimulators. ( 4.1 , 7.1 )»
FDA, section 4 · Open on DailyMed
CriticalRiociguat
«Phosphodiesterase Inhibitors: Concomitant administration of Adempas with specific PDE-5 inhibitors (such as sildenafil, tadalafil, or vardenafil) or nonspecific PDE-5 inhibitors (such as dipyridamole…»
FDA, section 4 · Open on DailyMed
MajorAtazanavir
«CONTRAINDICATIONS: a See Drug Interactions, Table 16 (7) for parenterally administered midazolam. b See Drug Interactions, Table 16 (7) for sildenafil when dosed as VIAGRA ® for erectile dysfunction.»
FDA, section 4 · Open on DailyMed
MajorClarithromycin
«DRUG INTERACTIONS: Sildenafil Tadalafil Vardenafil Use With Caution Sildenafil, Tadalafil, Vardenafil: Each of these phosphodiesterase inhibitors is primarily metabolized by CYP3A, and CYP3A will be…»
FDA, section 7 · Open on DailyMed
MajorDarunavir
«INHIBIDORES DE LA FOSFODIESTERASA 5 (PDE-5): La combinación de avanafilo y darunavir potenciado está contraindicada (ver sección 4.3). La administración simultánea de otros inhibidores de PDE-5 para…»
AEMPS, section 4.5 · Open on CIMA
MajorRitonavir
«Inhibidores de la fosfodiesterasa: El uso concomitante de sildenafilo para el tratamiento de la disfunción eréctil con ritonavir dosificado como agente antirretroviral o como potenciador…»
AEMPS, section 4.5 · Open on CIMA
MajorRitonavir
«CONTRAINDICATIONS: PDE5 Inhibitor: sildenafil (Revatio ® ) when used for the treatment of pulmonary arterial hypertension»
FDA, section 4 · Open on DailyMed
ModerateAmlodipine
«7.1. Impact of Other Drugs on Amlodipine: Sildenafil Monitor for hypotension when sildenafil is co-administered with amlodipine [ see Clinical Pharmacology (12.2) ].»
FDA, section 7 · Open on DailyMed
ModerateCiprofloxacin
«Sildenafilo: Se incrementó aproximadamente dos veces la C máx y la AUC de sildenafilo en voluntarios sanos tras la administración de una dosis oral de 50 mg administrada concomitantemente con 500 mg…»
AEMPS, section 4.5 · Open on CIMA
ModerateCiprofloxacin
«DRUG INTERACTIONS: Sildenafil Use with caution Two-fold increase in exposure Monitor for sildenafil toxicity [see Clinical Pharmacology ( 12.3 ) ] .»
FDA, section 7 · Open on DailyMed
ModerateClarithromycin
«Interacciones basadas en CYP3A: Se pueden considerar ajustes de dosis y cuando sea posible, las concentraciones séricas de los fármacos metabolizados principalmente por CYP3A se deben controlar de…»
AEMPS, section 4.5 · Open on CIMA
ModerateDoxazosin
«Uso con inhibidores de la PDE-5 : La administración concomitante de doxazosina con inhibidores de la fosfodiesterasa-5 (p.ej. sildenafilo, tadalafilo y vardenafilo) debe realizarse con precaución…»
AEMPS, section 4.4 · Open on CIMA
ModerateSilodosin
«Inhibidores de la PDE-5: Se han observado mínimas interacciones farmacodinámicas entre la silodosina y dosis máximas de sildenafilo o tadalafilo. En un ensayo controlado con placebo en el que…»
AEMPS, section 4.5 · Open on CIMA
ModerateSilodosin
«PDE5 Inhibitors: Co-administration of silodosin with a single dose of 100 mg sildenafil or 20 mg tadalafil was evaluated in a placebo-controlled clinical study that included 24 healthy male subjects…»
FDA, section 7 · Open on DailyMed
Amiodarone
«Sustratos CYP P450 3A4: Otros medicamentos metabolizados por el citocromo P450 3A4: ejemplos de dichos medicamentos son lidocaína, sirolimus, tacrolimus, sildenafilo, fentanilo, midazolam, triazolam…»
AEMPS, section 4.5 · Open on CIMA
Azithromycin
«Recomendación relativa a la administración conjunta: No se observaron cambios clínicamente significativos en la exposición de azitromicina o de los medicamentos administrados conjuntamente en los…»
AEMPS, section 4.5 · Open on CIMA

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Frequently asked

What is Sildenafil used for?

Sildenafil is evaluated for the following indications with varying evidence strength: Erectile dysfunction (evidence tier A), Pulmonary arterial hypertension (evidence tier A), Anti-aging and longevity (evidence tier F). See the full indication matrix with dosing and citations above on this page.

What are the side effects of Sildenafil?

Common side effects of Sildenafil (≥ 1 in 100): Headache (10–20 %), Flushing, Dyspepsia, Nasal congestion, Visual disturbances (blue tinge, photophobia, color perception changes), Back pain. See the Safety section for uncommon and serious reactions.

Is Sildenafil safe during pregnancy?

FDA categories were retired in 2015. Not indicated in women for ED. In pregnant patients with PAH, sildenafil is used on strict indication with pulmonologist and cardiologist input.

Is Sildenafil compatible with breastfeeding?

Not indicated in women for ED. In PAH patients, breastfeeding compatibility is assessed individually.

Can you drink alcohol while taking Sildenafil?

Alcohol is not contraindicated but increases hypotension risk.

Who should not take Sildenafil?

Sildenafil is contraindicated in: Concurrent nitrates (nitroglycerin, isosorbide dinitrate, amyl nitrite); Concurrent soluble guanylate cyclase stimulators (riociguat); Severe cardiovascular disease in which sexual activity is contraindicated; Severe hepatic impairment; Severe hypotension (SBP below 90). Full list in the Safety section.

Viagra causes erection in any man

PDE5 inhibitors require sexual stimulation — no stimulation, no effect. They are not aphrodisiacs.

Viagra triggers heart attacks

in patients without severe CAD and not on nitrates, PDE5 inhibitors are safe. Sexual activity itself does not 'trigger' MI in stable patients.

Viagra prolongs intercourse

it is for erectile dysfunction, not duration enhancement or for patients without erectile issues. Use for those purposes risks side effects without benefit.

Official sources

Direct links to regulator labels. Open in a new tab.

AEMPS / CIMA
EMALabel dated 09/15/2016
FDA / DailyMedLabel dated 08/31/2026

Other drugs in this group

Silodosin, Solifenacin, Tadalafil, Tamsulosin, Trospium, Dutasteride + Tamsulosin, Mirabegron, Tolterodine