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acetazolamideacetazolamide will increase the level or effect of sildenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism.

Key Point	Explanation	Advice
Take on an empty stomach	Food, especially high-fat meals, can delay onset	Take 30 min to 1 hour before activity
Avoid excessive alcohol	Can impair effectiveness and cause side effects	Limit intake during treatment
Report adverse effects	Headaches, vision changes, or priapism	Contact healthcare provider immediately
Do not exceed recommended dose	Risk of severe side effects	Follow medical advice
Store safely	Keep out of children’s reach	Proper storage is essential

acetazolamide will increase the level or effect of sildenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. anastrozoleanastrozole will increase the level or effect of sildenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism.

11. Sildenafil Tablets Description

Usual Pediatric Dose for:

anastrozole will increase the level or effect of sildenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism.

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cyclophosphamidecyclophosphamide will increase the level or effect of sildenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism.

Other uses for this medicine

cyclophosphamide will increase the level or effect of sildenafil by affecting sildenafil 50 mg tab hepatic/intestinal enzyme CYP3A4 metabolism.

5.8 Vaso-occlusive Crisis in Patients with Pulmonary Hypertension Secondary to Sickle Cell Disease

8.1 Pregnancy: Teratogenic effects

drospirenonedrospirenone will increase the level or effect of sildenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism.

• Sildenafil was originally developed to treat hypertension and angina.
• Its effect lasts approximately 4-6 hours depending on individual factors.
• Side effects may include muscle aches and skin rash in some cases.
• Discuss all medications with your doctor to avoid harmful interactions.
• Do not take sildenafil with fatty foods to ensure quicker action.

drospirenone will increase the level or effect of sildenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism.

Adverse Effects

Viagra Tablets

labetalolsildenafil increases effects of labetalol by pharmacodynamic synergism.

13.1 Carcinogenesis, Mutagenesis, Impairment of Fertility

larotrectiniblarotrectinib will increase the level or effect of sildenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. larotrectinib will increase the level or effect of sildenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. macitentanmacitentan increases levels of sildenafil products over the counter sildenafil by unspecified interaction mechanism. Systemic exposure of steady-state sildenafil (20 mg TID) increased by 15% during coadministration of macitentan (10 mg/day); this change is not considered clinically relevant. macitentan increases levels of sildenafil by unspecified interaction mechanism.

Factors That Influence the Right Dosage for You

Possible additive vasorelaxation, leading to low blood pressure. 50-mg doseHeadache (21%)Flushing (19%)100-mg dose H5Headache (28%)Flushing (18%)Dyspepsia (17%)Abnormal vision (11%) 25-mg doseFlushing (10%)Nasal congestion (4%)Dyspepsia (3%)Back pain (3%)Dizziness (3%)Myalgia (2%)Nausea (2%)Abnormal vision (1%)Rash (1%) 50-mg doseDyspepsia (9%)Nasal congestion (4%)Back pain (4%)Dizziness (4%)Nausea (3%)Abnormal vision (2%)Myalgia (2%)Rash (2%) 100-mg doseNasal congestion (9%)Back pain (4%)Myalgia (4%)Nausea (3%)Dizziness (3%)Rash (3%) <2% with potential causal relationshipBody as a whole: Face edema, photosensitivity reaction, shock, asthenia, pain, chills, accidental fall, abdominal pain, allergic reaction, chest pain, accidental injuryCardiovascular: Angina pectoris, AV block, migraine, syncope, tachycardia, palpitation, hypotension, postural hypotension, myocardial ischemia, cerebral thrombosis, cardiac arrest, heart failure, abnormal electrocardiogram, cardiomyopathyDigestive: Vomiting, glossitis, colitis, dysphagia, gastritis, gastroenteritis, esophagitis, stomatitis, dry mouth, liver function tests abnormal, rectal hemorrhage, gingivitisHemic and lymphatic: Anemia and leukopeniaMetabolic and nutritional: Thirst, edema, gout, unstable diabetes, hyperglycemia, peripheral edema, hyperuricemia, hypoglycemic reaction, hypernatremiaMusculoskeletal: Arthritis, arthrosis, myalgia, tendon rupture, tenosynovitis, bone pain, myasthenia, synovitisNervous: Ataxia, hypertonia, neuralgia, neuropathy, paresthesia, tremor, vertigo, depression, insomnia, somnolence, abnormal dreams, reflexes decreased, hypesthesiaRespiratory: Asthma, dyspnea, laryngitis, pharyngitis, sinusitis, bronchitis, sputum increased, cough increasedSkin and appendages: Urticaria, herpes simplex, pruritus, sweating, skin ulcer, contact dermatitis, exfoliative dermatitisSpecial senses: Sudden decrease or loss of hearing, mydriasis, conjunctivitis, photophobia, tinnitus, eye pain, ear pain, eye hemorrhage, cataract, dry eyesUrogenital: Cystitis, nocturia, urinary frequency, breast enlargement, urinary incontinence, abnormal ejaculation, genital edema and anorgasmia Body as a whole: Face edema, photosensitivity reaction, shock, asthenia, pain, chills, accidental fall, abdominal pain, allergic reaction, chest pain, accidental injury Cardiovascular: Angina pectoris, AV block, migraine, syncope, tachycardia, palpitation, hypotension, postural hypotension, myocardial ischemia, cerebral thrombosis, cardiac arrest, heart failure, abnormal electrocardiogram, cardiomyopathy Digestive: Vomiting, glossitis, colitis, dysphagia, gastritis, gastroenteritis, esophagitis, stomatitis, dry mouth, liver function tests abnormal, rectal hemorrhage, gingivitis Metabolic and nutritional: Thirst, edema, gout, unstable diabetes, hyperglycemia, peripheral edema, hyperuricemia, hypoglycemic reaction, hypernatremia Musculoskeletal: Arthritis, arthrosis, myalgia, tendon rupture, tenosynovitis, bone pain, myasthenia, synovitis Nervous: Ataxia, hypertonia, neuralgia, neuropathy, paresthesia, tremor, vertigo, depression, insomnia, somnolence, abnormal dreams, reflexes decreased, hypesthesia Respiratory: Asthma, dyspnea, laryngitis, pharyngitis, sinusitis, bronchitis, sputum increased, cough increased Skin and appendages: Urticaria, herpes simplex, pruritus, sweating, skin ulcer, contact dermatitis, exfoliative dermatitis Special senses: Sudden decrease or loss of hearing, mydriasis, conjunctivitis, photophobia, tinnitus, eye pain, ear pain, eye hemorrhage, cataract, dry eyes Urogenital: Cystitis, nocturia, urinary frequency, breast enlargement, urinary incontinence, abnormal ejaculation, genital edema and anorgasmia Cardiovascular and cerebrovascular: Serious cardiovascular (CV), cerebrovascular, and vascular events, including myocardial infarction, sudden cardiac death, ventricular arrhythmia, cerebrovascular hemorrhage, transient ischemic attack, hypertension, subarachnoid and intracerebral hemorrhages, and pulmonary hemorrhage (most, but not all, of these patients had preexisting CV risk factors) Hemic and lymphatic: vaso-occlusive crisis: In a small, prematurely terminated study of sildenafil in patients with pulmonary arterial hypertension (PAH) secondary to sickle cell disease, vaso-occlusive crises requiring hospitalization were commonly reported Nervous: Seizure, seizure recurrence, anxiety, and transient global amnesia Hearing: Cases of sudden decrease or loss of hearing reported postmarketing in temporal association with PDE5 inhibitors Ocular: Diplopia, temporary vision loss/decreased vision, ocular redness or bloodshot appearance, ocular burning, ocular swelling/pressure, increased intraocular pressure, retinal edema, retinal vascular disease or bleeding, and vitreous traction/detachment Nonarteritic anterior ischemic optic neuropathy (NAION), a cause of decreased vision including permanent loss of vision (reported rarely) Soluble guanylate cyclase (sGC) stimulators (eg, riociguat); concomitant use can cause hypotension Coadministration with nitrates (either regularly and/or intermittently) and nitric oxide donors Consistent with the effects of PDE5 inhibition on the nitric oxide/cyclic guanosine monophosphate pathway, PDE5 inhibitors may potentiate the hypotensive effects of nitrates A suitable time interval following PDE5 dosing for the safe administration of nitrates or nitric oxide donors has not been determined Elicits vasodilatory properties, resulting in mild and transient decreases in blood pressure; monitor for hypotension Use with caution in patients with anatomic deformation of penis (eg, angulation, cavernosal fibrosis, or Peyronie disease), conditions potentially predisposing to priapism (eg, sickle cell anemia, multiple myeloma, or leukemia), cardiovascular disease, bleeding disorders, active peptic ulcer disease, liver disease, renal impairment, multidrug antihypertensive regimens, retinitis pigmentosa, concomitant use of CYP3A4 inhibitors Pulmonary vasodilators may significantly worsen cardiovascular status of patients with pulmonary veno-occlusive disease Sudden decrease or loss of hearing, which may be accompanied by tinnitus and dizziness Stop sildenafil and seek medical care if a sudden loss of vision occurs in 1 or both eyes, which could be a sign of nonarteritic anterior ischemic optic neuropathy (NAION); use with caution, and only when the anticipated benefits outweigh the risks, most patients had underlying anatomic or vascular risk factors for developing NAION, including low cup to disc ratio (“crowded disc”); advise patients to seek immediate medical attention in the event of a sudden loss of vision May cause dose-related impairment of color discrimination; use in patients with retinitis pigmentosa not recommended Potential for cardiac risk with sexual activity in patients with preexisting cardiovascular disease; therefore, treatment for erectile dysfunction generally should not be instituted in men for whom sexual activity is inadvisable because of their underlying cardiovascular status Evaluate underlying causes of erectile dysfunction or BPH before initiating therapy In small, prematurely terminated study of patients with PAH secondary to sickle-cell disease, vaso-occlusive crises requiring hospitalization were more commonly reported by patients who received sildenafil than by those randomized to placebo; effectiveness of sildenafil in PAH secondary to sickle-cell anemia has not been established; the clinical relevance to men treated for erectile dysfunction with sildenafil is not known Epistaxis occurred in 13% of patients with PAH secondary to connective tissue disease (eg, scleroderma); this effect was not seen in idiopathic PAH; incidence was also higher in those receiving concomitant PO vitamin K antagonist therapy (9%) than in those not receiving such therapy (2%) CYP3A substrate (major route); CYP2C9 substrate (minor route) NitratesContraindicatedConsistent with its known effects on the nitric oxide/cGMP pathway, sildenafil was shown to potentiate the hypotensive effects of nitrates Consistent with its known effects on the nitric oxide/cGMP pathway, sildenafil was shown to potentiate the hypotensive effects of nitrates Strong CYP3A inhibitorsViagra: Modify dose; not to exceed single dose of 25 mg/48 hrRevatio: Not recommendedCoadministration increases systemic exposure of sildenafil and risk of adverse effects Viagra: Modify dose; not to exceed single dose of 25 mg/48 hr Coadministration increases systemic exposure of sildenafil and risk of adverse effects Moderate-to-strong CYP3A inducersRevatio: Modify dose; upward dose titration may be needed if coadministeredCoadministration with moderate-to-strong CYP3A inducers (eg, bosentan) decreases the sildenafil exposure and possibly reduces efficacy Revatio: Modify dose; upward dose titration may be needed if coadministered Coadministration with moderate-to-strong CYP3A inducers (eg, bosentan) decreases the sildenafil exposure and possibly reduces efficacy Other PDE5 inhibitorsAvoidAdditive adverse effects may occur if coadministered with other PDE5 inhibitors (eg, avanafil, tadalafil, vardenafil) Additive adverse effects may occur if coadministered with other PDE5 inhibitors (eg, avanafil, tadalafil, vardenafil) Alpha-blockers or antihypertensivesModify dose/cautionCoadministration may increase risk of hypotensionParticularly with higher doses used for erectile dysfunction Particularly with higher doses used for erectile dysfunction Limited published data from randomized controlled trials, case-controlled trials, and case series do not report a clear association with sildenafil and major birth defects, miscarriage, or adverse maternal or fetal outcomes when sildenafil is used during pregnancy; there are risks to mother and fetus from untreated pulmonary arterial hypertension Pregnant women with untreated pulmonary arterial hypertension are at risk for heart failure, stroke, preterm delivery, and maternal and fetal death Limited published data from a case report describe presence of sildenafil and its active metabolite in human milk; there is insufficient information about effects of sildenafil on breastfed infant and no information on effects of sildenafil on milk production; limited clinical data during lactation preclude a clear determination of risk of drug to an infant during lactation Controlled studies in pregnant women show no evidence of fetal risk. sildenafil increases effects of labetalol by pharmacodynamic synergism.

• PDE5 inhibitors like sildenafil improve blood flow in penile tissues.
• Use sildenafil only when planning sexual activity.
• Men taking antihypertensives should consult their doctor before use.
• Sildenafil can cause flushing and visual disturbances temporarily.
• Follow your healthcare provider’s instructions carefully for best results.

larotrectiniblarotrectinib will increase the level or effect of sildenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. larotrectinib will increase the level or effect of sildenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism.

• Regulatory status of sildenafil varies by country but generally requires a prescription.
• In the UK, it is a Prescription Only Medicine (POM) but can be prescribed by pharmacists.
• In some countries, it may be available in limited quantities without a prescription.
• The FDA requires a Risk Evaluation and Mitigation Strategy (REMS) for Revatio.
• The REMS is designed to inform healthcare providers about the serious risks.
• This includes the risk of use with nitrates and the potential for hearing loss.
• The medication is subject to controlled substance regulations in some regions.
• Traveling with prescription medication requires carrying it in original packaging.
• It is advisable to have a copy of the prescription or a doctor's note when traveling.
• Laws regarding the importation of prescription drugs are strict and vary.
• Always check the legal status of the medication in your destination country.

macitentanmacitentan increases levels of sildenafil products over the counter sildenafil by unspecified interaction mechanism.

• The medication should be stored at room temperature between 15-30°C (59-86°F).
• Keep the tablets in their original container, tightly closed.
• Protect from light and moisture; avoid storing in bathrooms or near sinks.
• Do not use the medication if the packaging is torn or shows signs of tampering.
• Check the expiration date printed on the bottle or blister pack before use.
• Properly discard any medication that is outdated or no longer needed.
• Do not flush medications down the toilet or pour them into a drain.
• Consult a pharmacist or local waste disposal company for proper disposal methods.
• Many communities have drug take-back programs for safe disposal.
• Keeping old medication increases the risk of accidental ingestion or misuse.
• Safe storage and disposal protect children, pets, and the environment.

Systemic exposure of steady-state sildenafil (20 mg TID) increased by 15% during coadministration of macitentan (10 mg/day); this change is not considered clinically relevant. macitentan increases levels of sildenafil by unspecified interaction mechanism. Possible additive vasorelaxation, leading to low blood pressure.

12.3 Pharmacokinetics

acetazolamideacetazolamide will increase the level or effect of sildenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. acetazolamide will increase the level or effect of sildenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. anastrozoleanastrozole will increase the level or effect of sildenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. anastrozole will increase the level or effect of sildenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. cyclophosphamidecyclophosphamide will increase the level or effect of sildenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism.

Comparing Sildenafil vs. Tadalafil Dosage

cyclophosphamide will increase the level or effect of sildenafil by affecting sildenafil 50 mg tab hepatic/intestinal enzyme CYP3A4 metabolism. drospirenonedrospirenone will increase the level or effect of sildenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. drospirenone will increase the level or effect of sildenafil by affecting hepatic/intestinal enzyme CYP3A4 metabolism. labetalolsildenafil increases effects of labetalol by pharmacodynamic synergism. sildenafil increases effects of labetalol by pharmacodynamic synergism. 50-mg doseHeadache (21%)Flushing (19%)100-mg dose H5Headache (28%)Flushing (18%)Dyspepsia (17%)Abnormal vision (11%) 25-mg doseFlushing (10%)Nasal congestion (4%)Dyspepsia (3%)Back pain (3%)Dizziness (3%)Myalgia (2%)Nausea (2%)Abnormal vision (1%)Rash (1%) 50-mg doseDyspepsia (9%)Nasal congestion (4%)Back pain (4%)Dizziness (4%)Nausea (3%)Abnormal vision (2%)Myalgia (2%)Rash (2%) 100-mg doseNasal congestion (9%)Back pain (4%)Myalgia (4%)Nausea (3%)Dizziness (3%)Rash (3%) <2% with potential causal relationshipBody as a whole: Face edema, photosensitivity reaction, shock, asthenia, pain, chills, accidental fall, abdominal pain, allergic reaction, chest pain, accidental injuryCardiovascular: Angina pectoris, AV block, migraine, syncope, tachycardia, palpitation, hypotension, postural hypotension, myocardial ischemia, cerebral thrombosis, cardiac arrest, heart failure, abnormal electrocardiogram, cardiomyopathyDigestive: Vomiting, glossitis, colitis, dysphagia, gastritis, gastroenteritis, esophagitis, stomatitis, dry mouth, liver function tests abnormal, rectal hemorrhage, gingivitisHemic and lymphatic: Anemia and leukopeniaMetabolic and nutritional: Thirst, edema, gout, unstable diabetes, hyperglycemia, peripheral edema, hyperuricemia, hypoglycemic reaction, hypernatremiaMusculoskeletal: Arthritis, arthrosis, myalgia, tendon rupture, tenosynovitis, bone pain, myasthenia, synovitisNervous: Ataxia, hypertonia, neuralgia, neuropathy, paresthesia, tremor, vertigo, depression, insomnia, somnolence, abnormal dreams, reflexes decreased, hypesthesiaRespiratory: Asthma, dyspnea, laryngitis, pharyngitis, sinusitis, bronchitis, sputum increased, cough increasedSkin and appendages: Urticaria, herpes simplex, pruritus, sweating, skin ulcer, contact dermatitis, exfoliative dermatitisSpecial senses: Sudden decrease or loss of hearing, mydriasis, conjunctivitis, photophobia, tinnitus, eye pain, ear pain, eye hemorrhage, cataract, dry eyesUrogenital: Cystitis, nocturia, urinary frequency, breast enlargement, urinary incontinence, abnormal ejaculation, genital edema and anorgasmia Body as a whole: Face edema, photosensitivity reaction, shock, asthenia, pain, chills, accidental fall, abdominal pain, allergic reaction, chest pain, accidental injury Cardiovascular: Angina pectoris, AV block, migraine, syncope, tachycardia, palpitation, hypotension, postural hypotension, myocardial ischemia, cerebral thrombosis, cardiac arrest, heart failure, abnormal electrocardiogram, cardiomyopathy Digestive: Vomiting, glossitis, colitis, dysphagia, gastritis, gastroenteritis, esophagitis, stomatitis, dry mouth, liver function tests abnormal, rectal hemorrhage, gingivitis Metabolic and nutritional: Thirst, edema, gout, unstable diabetes, hyperglycemia, peripheral edema, hyperuricemia, hypoglycemic reaction, hypernatremia Musculoskeletal: Arthritis, arthrosis, myalgia, tendon rupture, tenosynovitis, bone pain, myasthenia, synovitis Nervous: Ataxia, hypertonia, neuralgia, neuropathy, paresthesia, tremor, vertigo, depression, insomnia, somnolence, abnormal dreams, reflexes decreased, hypesthesia Respiratory: Asthma, dyspnea, laryngitis, pharyngitis, sinusitis, bronchitis, sputum increased, cough increased Skin and appendages: Urticaria, herpes simplex, pruritus, sweating, skin ulcer, contact dermatitis, exfoliative dermatitis Special senses: Sudden decrease or loss of hearing, mydriasis, conjunctivitis, photophobia, tinnitus, eye pain, ear pain, eye hemorrhage, cataract, dry eyes Urogenital: Cystitis, nocturia, urinary frequency, breast enlargement, urinary incontinence, abnormal ejaculation, genital edema and anorgasmia Cardiovascular and cerebrovascular: Serious cardiovascular (CV), cerebrovascular, and vascular events, including myocardial infarction, sudden cardiac death, ventricular arrhythmia, cerebrovascular hemorrhage, transient ischemic attack, hypertension, subarachnoid and intracerebral hemorrhages, and pulmonary hemorrhage (most, but not all, of these patients had preexisting CV risk factors) Hemic and lymphatic: vaso-occlusive crisis: In a small, prematurely terminated study of sildenafil in patients with pulmonary arterial hypertension (PAH) secondary to sickle cell disease, vaso-occlusive crises requiring hospitalization were commonly reported Nervous: Seizure, seizure recurrence, anxiety, and transient global amnesia Hearing: Cases of sudden decrease or loss of hearing reported postmarketing in temporal association with PDE5 inhibitors Ocular: Diplopia, temporary vision loss/decreased vision, ocular redness or bloodshot appearance, ocular burning, ocular swelling/pressure, increased intraocular pressure, retinal edema, retinal vascular disease or bleeding, and vitreous traction/detachment Nonarteritic anterior ischemic optic neuropathy (NAION), a cause of decreased vision including permanent loss of vision (reported rarely) Soluble guanylate cyclase (sGC) stimulators (eg, riociguat); concomitant use can cause hypotension Coadministration with nitrates (either regularly and/or intermittently) and nitric oxide donors Consistent with the effects of PDE5 inhibition on the nitric oxide/cyclic guanosine monophosphate pathway, PDE5 inhibitors may potentiate the hypotensive effects of nitrates A suitable time interval following PDE5 dosing for the safe administration of nitrates or nitric oxide donors has not been determined Elicits vasodilatory properties, resulting in mild and transient decreases in blood pressure; monitor for hypotension Use with caution in patients with anatomic deformation of penis (eg, angulation, cavernosal fibrosis, or Peyronie disease), conditions potentially predisposing to priapism (eg, sickle cell anemia, multiple myeloma, or leukemia), cardiovascular disease, bleeding disorders, active peptic ulcer disease, liver disease, renal impairment, multidrug antihypertensive regimens, retinitis pigmentosa, concomitant use of CYP3A4 inhibitors Pulmonary vasodilators may significantly worsen cardiovascular status of patients with pulmonary veno-occlusive disease Sudden decrease or loss of hearing, which may be accompanied by tinnitus and dizziness Stop sildenafil and seek medical care if a sudden loss of vision occurs in 1 or both eyes, which could be a sign of nonarteritic anterior ischemic optic neuropathy (NAION); use with caution, and only when the anticipated benefits outweigh the risks, most patients had underlying anatomic or vascular risk factors for developing NAION, including low cup to disc ratio (“crowded disc”); advise patients to seek immediate medical attention in the event of a sudden loss of vision May cause dose-related impairment of color discrimination; use in patients with retinitis pigmentosa not recommended Potential for cardiac risk with sexual activity in patients with preexisting cardiovascular disease; therefore, treatment for erectile dysfunction generally should not be instituted in men for whom sexual activity is inadvisable because of their underlying cardiovascular status Evaluate underlying causes of erectile dysfunction or BPH before initiating therapy In small, prematurely terminated study of patients with PAH secondary to sickle-cell disease, vaso-occlusive crises requiring hospitalization were more commonly reported by patients who received sildenafil than by those randomized to placebo; effectiveness of sildenafil in PAH secondary to sickle-cell anemia has not been established; the clinical relevance to men treated for erectile dysfunction with sildenafil is not known Epistaxis occurred in 13% of patients with PAH secondary to connective tissue disease (eg, scleroderma); this effect was not seen in idiopathic PAH; incidence was also higher in those receiving concomitant PO vitamin K antagonist therapy (9%) than in those not receiving such therapy (2%) CYP3A substrate (major route); CYP2C9 substrate (minor route) NitratesContraindicatedConsistent with its known effects on the nitric oxide/cGMP pathway, sildenafil was shown to potentiate the hypotensive effects of nitrates Consistent with its known effects on the nitric oxide/cGMP pathway, sildenafil was shown to potentiate the hypotensive effects of nitrates Strong CYP3A inhibitorsViagra: Modify dose; not to exceed single dose of 25 mg/48 hrRevatio: Not recommendedCoadministration increases systemic exposure of sildenafil and risk of adverse effects Viagra: Modify dose; not to exceed single dose of 25 mg/48 hr Coadministration increases systemic exposure of sildenafil and risk of adverse effects Moderate-to-strong CYP3A inducersRevatio: Modify dose; upward dose titration may be needed if coadministeredCoadministration with moderate-to-strong CYP3A inducers (eg, bosentan) decreases the sildenafil exposure and possibly reduces efficacy Revatio: Modify dose; upward dose titration may be needed if coadministered Coadministration with moderate-to-strong CYP3A inducers (eg, bosentan) decreases the sildenafil exposure and possibly reduces efficacy Other PDE5 inhibitorsAvoidAdditive adverse effects may occur if coadministered with other PDE5 inhibitors (eg, avanafil, tadalafil, vardenafil) Additive adverse effects may occur if coadministered with other PDE5 inhibitors (eg, avanafil, tadalafil, vardenafil) Alpha-blockers or antihypertensivesModify dose/cautionCoadministration may increase risk of hypotensionParticularly with higher doses used for erectile dysfunction Particularly with higher doses used for erectile dysfunction Limited published data from randomized controlled trials, case-controlled trials, and case series do not report a clear association with sildenafil and major birth defects, miscarriage, or adverse maternal or fetal outcomes when sildenafil is used during pregnancy; there are risks to mother and fetus from untreated pulmonary arterial hypertension Pregnant women with untreated pulmonary arterial hypertension are at risk for heart failure, stroke, preterm delivery, and maternal and fetal death Limited published data from a case report describe presence of sildenafil and its active metabolite in human milk; there is insufficient information about effects of sildenafil on breastfed infant and no information on effects of sildenafil on milk production; limited clinical data during lactation preclude a clear determination of risk of drug to an infant during lactation Controlled studies in pregnant women show no evidence of fetal risk.

Country	Prescription Requirement	Over-the-Counter Availability	Regulatory Body
USA	Yes	No	FDA
UK	Yes	No	MHRA
Canada	Yes	No	Health Canada
Australia	Yes	No	TGA
India	Yes (in some states)	Some brands available OTC	CDSCO