DOSAGE AND ADMINISTRATION

This metabolite has a phosphodiesterase selectivity profile similar to sildenafil and an in vitropotency for PDE-5 approximately 50% of the parent drug. In healthy volunteers, plasma concentrations of this metabolite are approximately 40% of those seen for sildenafil, so that the metabolite accounts for about 20% of sildenafil’s pharmacologic effects. In patients with PAH, however, the ratio of the metabolite to sildenafil is higher.

• 20mg sildenafil is often preferred for first-time users to assess response.
• Avoid grapefruit juice, as it can increase sildenafil levels in blood.
• Overuse or misuse can result in serious health complications.
• Check with a healthcare professional if side effects persist.
• Sildenafil does not protect against pregnancy or STDs.

Both sildenafil and the active metabolite have terminal half- lives of about 4 hours.After either oral or intravenous administration, sildenafil is excreted as metabolites predominantly in the feces (approximately 80% of the administered oral dose) and to a lesser extent in the urine (approximately 13% of the administered oral dose).Population PharmacokineticsAge, gender, race, and renal and hepatic function were included as factors assessed in the population pharmacokinetic model to evaluate sildenafil pharmacokinetics in patients with PAH. The dataset available for the population pharmacokinetic evaluation contained a wide range of demographic data and laboratory parameters associated with hepatic and renal function. None of these factors had a significant impact on sildenafil pharmacokinetics in patients with PAH.In patients with PAH, the average steady-state concentrations were 20 to 50% higher when compared to those of healthy volunteers. There was also a doubling of C minlevels compared to healthy volunteers. Both findings suggest a lower clearance and/or a higher oral bioavailability of sildenafil in patients with PAH compared to healthy volunteers.Pediatric PatientsPediatric use information is approved for Viatris Specialty LLC's, REVATIO ®(sildenafi) tablets. However, due to Viatris Specialty LLC's marketing exclusivity rights, this drug product is not labeled with that information .Geriatric PatientsHealthy elderly volunteers (65 years or over) had a reduced clearance of sildenafil, resulting in approximately 84% and 107% higher plasma concentrations of sildenafil and its active N- desmethyl metabolite, respectively, compared to those seen in healthy younger volunteers (18 to 45 years). Due to age-differences in plasma protein binding, the corresponding increase in the AUC of free (unbound) sildenafil and its active N-desmethyl metabolite were 45% and 57%, respectively.Renal ImpairmentIn volunteers with mild (CLcr = 50-80 mL/min) and moderate (CLcr = 30-49 mL/min) renal impairment, the pharmacokinetics of a single oral dose of sildenafil (50 mg) was not altered. In volunteers with severe (CLcr less than 30 mL/min) renal impairment, sildenafil clearance was reduced, resulting in approximately doubling of AUC and C maxcompared to age-matched volunteers with no renal impairment. In addition, N-desmethyl metabolite AUC and C maxvalues were significantly increased 200% and 79%, respectively, in patients with severe renal impairment compared to patients with normal renal function.Hepatic ImpairmentIn volunteers with mild to moderate hepatic cirrhosis (Child-Pugh class A and B), sildenafil clearance was reduced, resulting in increases in AUC (84%) and C max(47%) compared to age-matched volunteers with no hepatic impairment. Patients with severe hepatic impairment (Child- Pugh class C) have not been studied.Drug Interaction StudiesIn vitro studiesSildenafil metabolism is principally mediated by the CYP3A (major route) and CYP2C9 (minor route) cytochrome P450 isoforms. Therefore, inhibitors of these isoenzymes may reduce sildenafil clearance and inducers of these isoenzymes may increase sildenafil clearance.Sildenafil is a weak inhibitor of the cytochrome P450 isoforms 1A2, 2C9, 2C19, 2D6, 2E1 and 3A (IC50 greater than 150 µM).Sildenafil is not expected to affect the pharmacokinetics of compounds which are substrates of these CYP enzymes at clinically relevant concentrations.In vivo studiesThe effects of other drugs on sildenafil pharmacokinetics and the effects of sildenafil on the exposure to other drugs are shown in Figure 1 and Figure 2, respectively.Figure 1.

Frequently asked questions for Sildenafil

Effects of Other Drugs on Sildenafil PharmacokineticsFigure 2. Effects of Sildenafil on Other DrugsCYP3A Inhibitors and Beta BlockersPopulation pharmacokinetic analysis of data from patients in clinical trials indicated an approximately 30% reduction in sildenafil clearance when it was co-administered with mild/moderate CYP3A inhibitors and an approximately 34% reductions in sildenafil clearance when co-administered with beta-blockers. Sildenafil exposure at a dose of 80 mg three times a day without concomitant medication is shown to be 5-fold the exposure at a dose of 20 mg three times a day. This concentration range covers the same increased sildenafil exposure observed in specifically-designed drug interaction studies with CYP3A inhibitors (except for potent inhibitors such as ketoconazole, itraconazole, and ritonavir).CYP3A4 Inducers Including BosentanConcomitant administration of strong CYP3A inducers is expected to cause substantial decreases in plasma levels of sildenafil.Population pharmacokinetic analysis of data from patients in clinical trials indicated approximately 3-fold the sildenafil clearance when it was co-administered with mild CYP3A inducers.EpoprostenolThe mean reduction of sildenafil (80 mg three times a day) bioavailability when co-administered with epoprostenol was 28%, resulting in about 22% lower mean average steady state concentrations.

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Therefore, the slight decrease of sildenafil exposure in the presence of epoprostenol is not considered clinically relevant. The effect of sildenafil on epoprostenol pharmacokinetics is not known.No significant interactions were shown with tolbutamide (250 mg) or warfarin (40 mg), both of which are metabolized by CYP2C9.AlcoholSildenafil (50 mg) did not potentiate the hypotensive effect of alcohol in healthy volunteers with mean maximum blood alcohol levels of 0.08%. Sildenafil is an inhibitor of cGMP specific PDE-5 in the smooth muscle of the pulmonary vasculature, where PDE-5 is responsible for degradation of cGMP.

Key facts

5.3 Effects on the Eye

What should I tell my healthcare provider before taking sildenafil?

In patients with PAH, this can lead to vasodilation of the pulmonary women sildenafil vascular bed and, to a lesser degree, vasodilatation in the systemic circulation.

• Sildenafil does not cause spontaneous erections; stimulation is still required.
• Avoid using it if you have a history of stroke or severe heart disease.
• Consult a doctor especially if you have kidney or liver problems.
• The medication should not be used with certain antidepressants or antibiotics.
• Excessive dosing can lead to serious cardiovascular events.

Studies in vitrohave shown that sildenafil is selective for PDE5.

• Numerous drug interaction studies have been conducted with sildenafil.
• Co-administration with nitrates causes synergistic blood pressure lowering.
• This interaction can lead to life-threatening hypotension and cardiovascular collapse.
• Alpha-blockers (e.g., tamsulosin) can enhance the blood pressure-lowering effect.
• A separation of at least 4 hours between alpha-blocker and sildenafil dose is advised.
• HIV protease inhibitors significantly increase sildenafil AUC (up to 11-fold).
• A maximum sildenafil dose of 25mg in a 48-hour period is recommended with ritonavir.
• Other CYP3A4 inhibitors require similar dose reductions and cautious use.
• No significant interaction was observed with tolbutamide, warfarin, or alcohol.
• Alcohol can increase the potential for orthostatic hypotension and dizziness.
• Always assume a potential interaction exists with any new medication.

This lower selectivity is thought to be the basis for abnormalities related to color vision observed with higher doses or plasma levels [see Clinical Pharmacology (12.2)] .

In case of emergency/overdose

Effects of Sildenafil on Other DrugsCYP3A Inhibitors and Beta BlockersPopulation pharmacokinetic analysis of data from patients in clinical trials indicated an approximately 30% reduction in sildenafil clearance when it was co-administered with mild/moderate CYP3A inhibitors and an approximately 34% reductions in sildenafil clearance when co-administered with beta-blockers. Sildenafil exposure at a dose of 80 mg three times a day without concomitant medication is shown to be 5-fold the exposure at a dose of 20 mg three times a day. This concentration range covers the same increased sildenafil exposure observed in specifically-designed drug interaction studies with CYP3A inhibitors (except for potent inhibitors such as ketoconazole, itraconazole, and ritonavir).CYP3A4 Inducers Including BosentanConcomitant administration of strong CYP3A inducers is expected to cause substantial decreases in plasma levels of sildenafil.Population pharmacokinetic analysis of data from patients in clinical trials indicated approximately 3-fold the sildenafil clearance when it was co-administered with mild CYP3A inducers.EpoprostenolThe mean reduction of sildenafil (80 mg three times a day) bioavailability when co-administered with epoprostenol was 28%, resulting in about 22% lower mean average steady state concentrations. Therefore, the slight decrease of sildenafil exposure in the presence of epoprostenol is not considered clinically relevant. The effect of sildenafil on epoprostenol pharmacokinetics is not known.No significant interactions were shown with tolbutamide (250 mg) or warfarin (40 mg), both of which are metabolized by CYP2C9.AlcoholSildenafil (50 mg) did not potentiate the hypotensive effect of alcohol in healthy volunteers with mean maximum blood alcohol levels of 0.08%.

Dosage Forms & Strengths

Sildenafil is an inhibitor of cGMP specific PDE-5 in the smooth muscle of the pulmonary vasculature, where PDE-5 is responsible for degradation of cGMP. In patients with PAH, this can lead to vasodilation of the pulmonary women sildenafil vascular bed and, to a lesser degree, vasodilatation in the systemic circulation. Studies in vitrohave shown that sildenafil is selective for PDE5. This lower selectivity is thought to be the basis for abnormalities related to color vision observed with higher doses or plasma levels [see Clinical Pharmacology (12.2)] . In addition to pulmonary vascular smooth muscle and the corpus cavernosum, PDE5 is also found in other tissues including vascular and visceral smooth muscle and in platelets.

Factors That Influence the Right Dosage for You

The inhibition of PDE5 in these tissues by sildenafil may be the basis for the enhanced platelet anti-aggregatory activity of nitric oxide observed in vitro, and the mild peripheral arterial-venous dilatation in vivo. Patients on all sildenafil doses achieved a statistically significant reduction in mean pulmonary arterial pressure (mPAP) compared to those on placebo in a study with no background vasodilators [see SUPER-1 in Clinical Studies (14)] . The relationship between these effects and improvements in 6-minute walk distance is unknown. Changes from Baseline in Hemodynamic Parameters at Week 12 [mean (95% CI)] for the Sildenafil 20 mg Three Times a Day and Placebo Group mPAP = mean pulmonary arterial pressure; PVR = pulmonary vascular resistance; SVR = systemic vascular resistance; RAP = right atrial pressure; CO = cardiac output; HR = heart rate. *The number of patients per treatment group varied slightly for each parameter due to missing assessments. In addition to pulmonary vascular smooth muscle and the corpus cavernosum, PDE5 is also found in other tissues including vascular and visceral smooth muscle and in platelets. The inhibition of PDE5 in these tissues by sildenafil may be the basis for the enhanced platelet anti-aggregatory activity of nitric oxide observed in vitro, and the mild peripheral arterial-venous dilatation in vivo. Patients on all sildenafil doses achieved a statistically significant reduction in mean pulmonary arterial pressure (mPAP) compared to those on placebo in a study with no background vasodilators [see SUPER-1 in Clinical Studies (14)] . The relationship between these effects and improvements in 6-minute walk distance is unknown.

Other Comments

This metabolite has a phosphodiesterase selectivity profile similar to sildenafil and an in vitropotency for PDE-5 approximately 50% of the parent drug. In healthy volunteers, plasma concentrations of this metabolite are approximately 40% of those seen for sildenafil, so that the metabolite accounts for about 20% of sildenafil’s pharmacologic effects. In patients with PAH, however, the ratio of the metabolite to sildenafil is higher. Both sildenafil and the active metabolite have terminal half- lives of about 4 hours.After either oral or intravenous administration, sildenafil is excreted as metabolites predominantly in the feces (approximately 80% of the administered oral dose) and to a lesser extent in the urine (approximately 13% of the administered oral dose).Population PharmacokineticsAge, gender, race, and renal and hepatic function were included as factors assessed in the population pharmacokinetic model to evaluate sildenafil pharmacokinetics in patients with PAH. The dataset available for the population pharmacokinetic evaluation contained a wide range of demographic data and laboratory parameters associated with hepatic and renal function.

What should I know about sildenafil before taking it?

None of these factors had a significant impact on sildenafil pharmacokinetics in patients with PAH.In patients with PAH, the average steady-state concentrations were 20 to 50% higher when compared to those of healthy volunteers. There was also a doubling of C minlevels compared to healthy volunteers. Both findings suggest a lower clearance and/or a higher oral bioavailability of sildenafil in patients with PAH compared to healthy volunteers.Pediatric PatientsPediatric use information is approved for Viatris Specialty LLC's, REVATIO ®(sildenafi) tablets. However, due to Viatris Specialty LLC's marketing exclusivity rights, this drug product is not labeled with that information .Geriatric PatientsHealthy elderly volunteers (65 years or over) had a reduced clearance of sildenafil, resulting in approximately 84% and 107% higher plasma concentrations of sildenafil and its active N- desmethyl metabolite, respectively, compared to those seen in healthy younger volunteers (18 to 45 years). Due to age-differences in plasma protein binding, the corresponding increase in the AUC of free (unbound) sildenafil and its active N-desmethyl metabolite were 45% and 57%, respectively.Renal ImpairmentIn volunteers with mild (CLcr = 50-80 mL/min) and moderate (CLcr = 30-49 mL/min) renal impairment, the pharmacokinetics of a single oral dose of sildenafil (50 mg) was not altered.

12.3 Pharmacokinetics

In volunteers with severe (CLcr less than 30 mL/min) renal impairment, sildenafil clearance was reduced, resulting in approximately doubling of AUC and C maxcompared to age-matched volunteers with no renal impairment. In addition, N-desmethyl metabolite AUC and C maxvalues were significantly increased 200% and 79%, respectively, in patients with severe renal impairment compared to patients with normal renal function.Hepatic ImpairmentIn volunteers with mild to moderate hepatic cirrhosis (Child-Pugh class A and B), sildenafil clearance was reduced, resulting in increases in AUC (84%) and C max(47%) compared to age-matched volunteers with no hepatic impairment. Patients with severe hepatic impairment (Child- Pugh class C) have not been studied.Drug Interaction StudiesIn vitro studiesSildenafil metabolism is principally mediated by the CYP3A (major route) and CYP2C9 (minor route) cytochrome P450 isoforms. Therefore, inhibitors of these isoenzymes may reduce sildenafil clearance and inducers of these isoenzymes may increase sildenafil clearance.Sildenafil is a weak inhibitor of the cytochrome P450 isoforms 1A2, 2C9, 2C19, 2D6, 2E1 and 3A (IC50 greater than 150 µM).Sildenafil is not expected to affect the pharmacokinetics of compounds which are substrates of these CYP enzymes at clinically relevant concentrations.In vivo studiesThe effects of other drugs on sildenafil pharmacokinetics and the effects of sildenafil on the exposure to other drugs are shown in Figure 1 and Figure 2, respectively.Figure 1. Effects of Other Drugs on Sildenafil PharmacokineticsFigure 2. Changes from Baseline in Hemodynamic Parameters at Week 12 [mean (95% CI)] for the Sildenafil 20 mg Three Times a Day and Placebo Group mPAP = mean pulmonary arterial pressure; PVR = pulmonary vascular resistance; SVR = systemic vascular resistance; RAP = right atrial pressure; CO = cardiac output; HR = heart rate.

Aspect	Details	Notes
Active Ingredient	Sildenafil citrate	Used for erectile dysfunction
Dosage Strength	20 mg per tablet	Common dosage for initial treatments
Recommended Use	Oral administration	Taken with water before sexual activity
Availability	Over-the-counter in some countries	Prescription required in others
Onset of Action	Typically 30-60 minutes	Varies by individual

*The number of patients per treatment group varied slightly for each parameter due to missing assessments. Single oral doses of sildenafil 100 mg administered to healthy volunteers produced decreases in supine blood pressure (mean maximum decrease in systolic/diastolic blood pressure of 8/5 mmHg). Larger effects were recorded among patients receiving concomitant nitrates [see Contraindications (4)] .

• The future of sildenafil includes research into new therapeutic areas.
• Investigations are ongoing for its use in heart failure with preserved ejection fraction.
• Studies examine its potential benefits in Alzheimer's disease and vascular dementia.
• Its application in jet lag and sleep cycle disorders is being explored.
• Research continues for its use in various forms of female sexual dysfunction.
• Novel delivery systems, like microneedle patches, are in preclinical development.
• Combination therapies with other agents for enhanced effect are being tested.
• The search for more selective PDE5 inhibitors with fewer side effects continues.
• Genetic factors influencing drug response are an area of pharmacogenomic research.
• Sildenafil remains a valuable tool for basic research in vascular biology.
• Its story is a continuing one of scientific discovery and application.

Single oral doses of sildenafil up to 100 mg in healthy volunteers produced no clinically relevant effects on electrocardiogram (ECG). After chronic dosing of 80 mg three times a day to patients with PAH, no clinically relevant effects on ECG were reported. After chronic dosing of 80 mg three times a day sildenafil to healthy volunteers, the largest mean change from baseline in supine systolic and supine diastolic blood pressures was a decrease of 9.0 mmHg and 8.4 mmHg, respectively. After chronic dosing of 80 mg three times a day sildenafil to patients with systemic hypertension, the mean change from baseline in systolic and diastolic blood pressures was a decrease of 9.4 and 9.1 mmHg, respectively. After chronic dosing of 80 mg three times a day sildenafil to patients with PAH, lesser reductions than above in systolic and diastolic blood pressures were observed (a decrease in both of 2 mmHg). At single oral doses of 100 mg and 200 mg, transient dose-related impairment of color discrimination (blue/green) was detected using the Farnsworth-Munsell 100-hue test, with peak effects near the time of peak plasma levels. An evaluation of visual function at doses up to 200 mg revealed no effects of sildenafil on visual acuity, intraocular pressure, or pupillometry. Sildenafil is rapidly absorbed after oral administration, with a mean absolute bioavailability of 41% (25 to 63%). Protein binding is independent of total drug concentrations. Bioequivalence was established between the 20 mg tablet and the 10 mg/mL oral suspension when administered as a 20 mg single oral dose of sildenafil (as citrate). Sildenafil is cleared predominantly by the CYP3A (major route) and cytochrome P450 2C9 (CYP2C9, minor route) hepatic microsomal isoenzymes. Both sildenafil and the active metabolite have terminal half- lives of about 4 hours.

What other information should I know?

Single oral doses of sildenafil 100 mg administered to healthy volunteers produced decreases in supine blood pressure (mean maximum decrease in systolic/diastolic blood pressure of 8/5 mmHg). Larger effects were recorded among patients receiving concomitant nitrates [see Contraindications (4)] . Single oral doses of sildenafil up to 100 mg in healthy volunteers produced no clinically relevant effects on electrocardiogram (ECG). After chronic dosing of 80 mg three times a day to patients with PAH, no clinically relevant effects on ECG were reported. After chronic dosing of 80 mg three times a day sildenafil to healthy volunteers, the largest mean change from baseline in supine systolic and supine diastolic blood pressures was a decrease of 9.0 mmHg and 8.4 mmHg, respectively.

Vybrique Oral Film

After chronic dosing of 80 mg three times a day sildenafil to patients with systemic hypertension, the mean change from baseline in systolic and diastolic blood pressures was a decrease of 9.4 and 9.1 mmHg, respectively. After chronic dosing of 80 mg three times a day sildenafil to patients with PAH, lesser reductions than above in systolic and diastolic blood pressures were observed (a decrease in both of 2 mmHg). At single oral doses of 100 mg and 200 mg, transient dose-related impairment of color discrimination (blue/green) was detected using the Farnsworth-Munsell 100-hue test, with peak effects near the time of peak plasma levels. An evaluation of visual function at doses up to 200 mg revealed no effects of sildenafil on visual acuity, intraocular pressure, or pupillometry. Sildenafil is rapidly absorbed after oral administration, with a mean absolute bioavailability of 41% (25 to 63%).

How does sildenafil work (mechanism of action)?

Protein binding is independent of total drug concentrations. Bioequivalence was established between the 20 mg tablet and the 10 mg/mL oral suspension when administered as a 20 mg single oral dose of sildenafil (as citrate). Sildenafil is cleared predominantly by the CYP3A (major route) and cytochrome P450 2C9 (CYP2C9, minor route) hepatic microsomal isoenzymes. Both sildenafil and the active metabolite have terminal half- lives of about 4 hours. After either oral or intravenous administration, sildenafil is excreted as metabolites predominantly in the feces (approximately 80% of the administered oral dose) and to a lesser extent in the urine (approximately 13% of the administered oral dose). After either oral or intravenous administration, sildenafil is excreted as metabolites predominantly in the feces (approximately 80% of the administered oral dose) and to a lesser extent in the urine (approximately 13% of the administered oral dose).