The maximum recommended dose of 100 mg sildenafil was not evaluated in this study [see Drug Interactions(7.5)].Effects of Sildenafil Tablets on Cardiac Parameters:Single oral doses of sildenafil up to 100 mg produced no clinically relevant changes in the ECGs of normal male volunteers.Studies have produced relevant data on the effects of sildenafil tablets on cardiac output.
Sildenafil tablets are often stored in their original packaging to avoid contamination. Use only the amount prescribed; more does not mean better results. Sildenafil helps improve erectile function but doesn’t increase libido. The tablets are designed for rapid and effective absorption. Always inform your doctor about existing health conditions before use. Some brands of sildenafil are marketed as "white tablets" for easy recognition. The medication can cause a mild increase in blood flow to other body parts. Avoid caffeine or heavy meals before taking sildenafil for better results. The safety and efficacy of sildenafil are supported by numerous clinical trials. Never take expired sildenafil tablets, as their safety can’t be guaranteed. Regular blood pressure checks are recommended when using sildenafil long-term.
In one small, open-label, uncontrolled, pilot study, eight patients with stable ischemic heart disease underwent Swan-Ganz catheterization. A total dose of 40 mg sildenafil was administered by four intravenous infusions.The results from this pilot study are shown in Table 3; the mean resting systolic and diastolic blood pressures decreased by 7% and 10% compared to baseline in these patients. Mean resting values for right atrial pressure, pulmonary artery pressure, pulmonary artery occluded pressure and cardiac output decreased by 28%, 28%, 20% and 7% respectively.
Risks and warnings for Sildenafil (Viagra)
The maximum recommended dose of 100 mg sildenafil was not evaluated in this study [see Drug Interactions(7.5)].Effects of Sildenafil Tablets on Cardiac Parameters:Single oral doses of sildenafil up to 100 mg produced no clinically relevant changes in the ECGs of normal male volunteers.Studies have produced relevant data on the effects of sildenafil tablets on cardiac output. In one small, open-label, uncontrolled, pilot study, eight patients with stable ischemic heart disease underwent Swan-Ganz catheterization. A total dose of 40 mg sildenafil was administered by four intravenous infusions.The results from this pilot study are shown in Table 3; the mean resting systolic and diastolic blood pressures decreased by 7% and 10% compared to baseline in these patients. Mean resting values for right atrial pressure, pulmonary artery pressure, pulmonary artery occluded pressure and cardiac output decreased by 28%, 28%, 20% and 7% respectively. Even though this total dosage produced plasma sildenafil concentrations which were approximately 2 to 5 times higher than the mean maximum plasma concentrations following a single oral dose of 100 mg in healthy male volunteers, the hemodynamic response to exercise was preserved in these patients.Table 3.
Is Teva sildenafil the same as Viagra?
Hemodynamic Data in Patients with Stable Ischemic Heart Disease after Intravenous Administration of 40 mg of SildenafilIn a double-blind study, 144 patients with erectile dysfunction and chronic stable angina limited by exercise, not receiving chronic oral nitrates, were randomized to a single dose of placebo or sildenafil tablets 100 mg 1 hour prior to exercise testing. The primary endpoint was time to limiting angina in the evaluable cohort. The mean times (adjusted for baseline) to onset of limiting angina were 423.6 and 403.7 seconds for sildenafil (N=70) and placebo, respectively. These results demonstrated that the effect of sildenafil tablets on the primary endpoint was statistically non-inferior to placebo.Effects of Sildenafil Tablets on Vision:At single oral doses of 100 mg and 200 mg, transient dose-related impairment of color discrimination was detected using the Farnsworth-Munsell 100-hue test, with peak effects near the time of peak plasma levels. This finding is consistent with the inhibition of PDE6, which is involved in phototransduction in the retina. Even though this total dosage produced plasma sildenafil concentrations which were approximately 2 to 5 times higher than the mean maximum plasma concentrations following a single oral dose of 100 mg in healthy male volunteers, the hemodynamic response to exercise was preserved in these patients.Table 3. Hemodynamic Data in Patients with Stable Ischemic Heart Disease after Intravenous Administration of 40 mg of SildenafilIn a double-blind study, 144 patients with erectile dysfunction and chronic stable angina limited by exercise, not receiving chronic oral nitrates, were randomized to a single dose of placebo or sildenafil tablets 100 mg 1 hour prior to exercise testing. The primary endpoint was time to limiting angina in the evaluable cohort. The mean times (adjusted for baseline) to onset of limiting angina were 423.6 and 403.7 seconds for sildenafil (N=70) and placebo, respectively. These results demonstrated that the effect of sildenafil tablets on the primary endpoint was statistically non-inferior to placebo.Effects of Sildenafil Tablets on Vision:At single oral doses of 100 mg and 200 mg, transient dose-related impairment of color discrimination was detected using the Farnsworth-Munsell 100-hue test, with peak effects near the time of peak plasma levels.
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This finding is consistent with the inhibition of PDE6, which is involved in phototransduction in the retina. Subjects in the study reported this finding as difficulties in discriminating blue/green.
7.4 Ritonavir and other CYP3A4 inhibitors
The major circulating blue sildenafil metabolite results from N-desmethylation of sildenafil, and is itself further metabolized. This metabolite has a PDE selectivity profile similar to sildenafil and an in vitropotency for PDE5 approximately 50% of the parent drug. 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.After either oral or intravenous administration, sildenafil is excreted as metabolites predominantly in the feces (approximately 80% of administered oral dose) and to a lesser extent in the urine (approximately 13% of the administered oral dose). Similar values for pharmacokinetic parameters were seen in normal volunteers and in the patient population, using a population pharmacokinetic approach.Pharmacokinetics in Special PopulationsGeriatrics:Healthy elderly volunteers (65 years or over) had a reduced clearance of sildenafil, resulting in approximately 84% and 107% higher plasma AUC values 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 activeN-desmethyl metabolite were 45% and 57%, respectively [ see Dosage and Administration (2.5),and Use in Specific Populations (8.5)]Renal Impairment:In volunteers with mild (CLcr=50 to 80 mL/min) and moderate (CLcr=30 to 49 mL/min) renal impairment, the pharmacokinetics of a single oral dose of sildenafil tablets (50 mg) were not altered.
What are the most common side effects of sildenafil?
In volunteers with severe (CLcr <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 [see Dosage and Administration (2.5),and Use in Specific Populations (8.6)].In addition, N-desmethyl metabolite AUC and C maxvalues significantly increased by 200% and 79%, respectively in subjects with severe renal impairment compared to subjects with normal renal function.Hepatic Impairment:In volunteers with hepatic impairment (Child-Pugh Class A and B), sildenafil clearance was reduced, resulting in increases in AUC (85%) and C max(47%) compared to age-matched volunteers with no hepatic impairment. The pharmacokinetics of sildenafil in patients with severely impaired hepatic function (Child-Pugh Class C) have not been studied [see Dosage and Administration (2.5), and Use in Specific Populations (8.7)].Therefore, age >65, hepatic impairment and severe renal impairment are associated with increased plasma levels of sildenafil. A starting oral dose of 25 mg should be considered in those patients [see Dosage and Administration (2.5)].Drug Interaction StudiesEffects of Other Drugs on Sildenafil TabletsSildenafil metabolism is principally mediated by CYP3A4 (major route) and CYP2C9 (minor route). Therefore, inhibitors of these isoenzymes may reduce sildenafil clearance and inducers of these isoenzymes may increase sildenafil clearance. The concomitant use of erythromycin or strong CYP3A4 inhibitors (e.g., saquinavir, ketoconazole, itraconazole) as well as the nonspecific CYP inhibitor, cimetidine, is associated with increased plasma levels of sildenafil [see Dosage and Administration (2.4)].In vivostudies:Cimetidine (800 mg), a nonspecific CYP inhibitor, caused a 56% increase in plasma sildenafil concentrations when co-administered with sildenafil tablets (50 mg) to healthy volunteers.When a single 100 mg dose of sildenafil tablets were administered with erythromycin, a moderate CYP3A4 inhibitor, at steady state (500 mg bid for 5 days), there was a 160% increase in sildenafil C maxand a 182% increase in sildenafil AUC. An evaluation of visual function at doses up to twice the maximum recommended dose revealed no effects of sildenafil tablets on visual acuity, intraocular pressure, or pupillometry.Effects of Sildenafil Tablets on Sperm:There was no effect on sperm motility or morphology after single 100 mg oral doses of sildenafil tablets in healthy volunteers.12.3 PharmacokineticsSildenafil tablets are rapidly absorbed after oral administration, with a mean absolute bioavailability of 41% (range 25 to 63%).
The bottom line
In addition, in a study performed in healthy male volunteers, co-administration of the HIV protease inhibitor saquinavir, also a CYP3A4 inhibitor, at steady state (1200 mg tid) with sildenafil tablets (100 mg single dose) resulted in a 140% increase in sildenafil C maxand a 210% increase in sildenafil AUC. A stronger CYP3A4 inhibitor such as ketoconazole or itraconazole could be expected to have greater effect than that seen with saquinavir. Population pharmacokinetic data from patients in clinical trials also indicated a reduction in sildenafil clearance when it was co- administered with CYP3A4 inhibitors (such as ketoconazole, erythromycin, or cimetidine) [see Dosage and Administration (2.4)and Drug Interactions (7.4)].In another study in healthy male volunteers, co-administration with the HIV protease inhibitor ritonavir, which is a highly potent P450 inhibitor, at steady state (500 mg bid) with sildenafil tablets (100 mg single dose) resulted in a 300% (4-fold) increase in sildenafil C maxand a 1000% (11-fold) increase in sildenafil plasma AUC. At 24 hours the plasma levels of sildenafil were still approximately 200 ng/mL, compared to approximately 5 ng/mL when sildenafil was dosed alone. This is consistent with ritonavir’s marked effects on a broad range of P450 substrates.
Sildenafil: what you need to know
Sildenafil tablets had no effect on ritonavir pharmacokinetics [see Dosage and Administration (2.4)and Drug Interactions (7.4)].Although the interaction between other protease inhibitors and sildenafil has not been studied, their concomitant use is expected to increase sildenafil levels.In a study of healthy male volunteers, co-administration of sildenafil at steady state (80 mg t.i.d.) with endothelin receptor antagonist bosentan (a moderate inducer of CYP3A4, CYP2C9 and possibly of CYP2C19) at steady state (125 mg b.i.d.) resulted in a 63% decrease of sildenafil AUC and a 55% decrease in sildenafil C max. The pharmacokinetics of sildenafil are dose-proportional over the recommended dose range.
White sildenafil tablets may be counterfeit if lacking proper packaging. The expiry date on sildenafil tablets is important for safety. For improved absorption, take sildenafil with a light meal or on an empty stomach. Sildenafil should not be used more than once per day. Common side effects may include nasal congestion and muscle pain. Regular use without consulting a doctor can mask underlying health issues. Some users experience temporary vision disturbances after taking sildenafil. Sildenafil is approved by regulatory agencies like the FDA. Do not mix sildenafil with recreational drugs or alcohol. Always follow the prescribed dosage specified by your healthcare provider. Discontinue use and seek medical advice if adverse effects occur.
It is eliminated predominantly by hepatic metabolism (mainly CYP3A4) and is converted to an active metabolite with properties similar to the parent, sildenafil. Both sildenafil and the metabolite have terminal half lives of about 4 hours.Mean sildenafil plasma concentrations measured after the administration of a single oral dose of 100 mg to healthy male volunteers is depicted below:Figure 5: Mean Sildenafil Plasma Concentrationsin Healthy Male Volunteers.Absorption and Distribution: Sildenafil tablets are rapidly absorbed. Maximum observed plasma concentrations are reached within 30 to 120 minutes (median 60 minutes) of oral dosing in the fasted state. When sildenafil tablets are taken with a high fat meal, the rate of absorption is reduced, with a mean delay in T maxof 60 minutes and a mean reduction in C maxof 29%. The mean steady state volume of distribution (Vss) for sildenafil is 105 L, indicating distribution into the tissues. Sildenafil and its major circulating N-desmethyl metabolite are both approximately 96% bound to plasma proteins.
Frequently asked questions
Subjects in the study reported this finding as difficulties in discriminating blue/green. An evaluation of visual function at doses up to twice the maximum recommended dose revealed no effects of sildenafil tablets on visual acuity, intraocular pressure, or pupillometry.Effects of Sildenafil Tablets on Sperm:There was no effect on sperm motility or morphology after single 100 mg oral doses of sildenafil tablets in healthy volunteers.12.3 PharmacokineticsSildenafil tablets are rapidly absorbed after oral administration, with a mean absolute bioavailability of 41% (range 25 to 63%). The pharmacokinetics of sildenafil are dose-proportional over the recommended dose range. It is eliminated predominantly by hepatic metabolism (mainly CYP3A4) and is converted to an active metabolite with properties similar to the parent, sildenafil. Both sildenafil and the metabolite have terminal half lives of about 4 hours.Mean sildenafil plasma concentrations measured after the administration of a single oral dose of 100 mg to healthy male volunteers is depicted below:Figure 5: Mean Sildenafil Plasma Concentrationsin Healthy Male Volunteers.Absorption and Distribution: Sildenafil tablets are rapidly absorbed.
Altitude sickness
Maximum observed plasma concentrations are reached within 30 to 120 minutes (median 60 minutes) of oral dosing in the fasted state. When sildenafil tablets are taken with a high fat meal, the rate of absorption is reduced, with a mean delay in T maxof 60 minutes and a mean reduction in C maxof 29%. The mean steady state volume of distribution (Vss) for sildenafil is 105 L, indicating distribution into the tissues. Sildenafil and its major circulating N-desmethyl metabolite are both approximately 96% bound to plasma proteins. Protein binding is independent of total drug concentrations.Based upon measurements of sildenafil in semen of healthy volunteers 90 minutes after dosing, less than 0.001% of the administered dose may appear in the semen of patients.Metabolism and Excretion:Sildenafil is cleared predominantly by the CYP3A4 (major route) and CYP2C9 (minor route) hepatic microsomal isoenzymes. Protein binding is independent of total drug concentrations.Based upon measurements of sildenafil in semen of healthy volunteers 90 minutes after dosing, less than 0.001% of the administered dose may appear in the semen of patients.Metabolism and Excretion:Sildenafil is cleared predominantly by the CYP3A4 (major route) and CYP2C9 (minor route) hepatic microsomal isoenzymes. The major circulating blue sildenafil metabolite results from N-desmethylation of sildenafil, and is itself further metabolized.
Ingredient
Quantity per Tablet
Function
Notes
Sildenafil Citrate
50 mg
Active ingredient
Main component
Microcrystalline Cellulose
20 mg
Filler and binder
Increases tablet stability
Magnesium Stearate
2 mg
Lubricant
Ensures smooth manufacturing
Starch
10 mg
Diluent
Helps with disintegration
This metabolite has a PDE selectivity profile similar to sildenafil and an in vitropotency for PDE5 approximately 50% of the parent drug. 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.After either oral or intravenous administration, sildenafil is excreted as metabolites predominantly in the feces (approximately 80% of administered oral dose) and to a lesser extent in the urine (approximately 13% of the administered oral dose). Similar values for pharmacokinetic parameters were seen in normal volunteers and in the patient population, using a population pharmacokinetic approach.Pharmacokinetics in Special PopulationsGeriatrics:Healthy elderly volunteers (65 years or over) had a reduced clearance of sildenafil, resulting in approximately 84% and 107% higher plasma AUC values of sildenafil and its active N-desmethyl metabolite, respectively, compared to those seen in healthy younger volunteers (18 to 45 years).
Country/Region
Legal Status
Regulatory Agency
Prescription Needed
Notes
United States
Prescription-only
FDA
Yes
Class II controlled substance
European Union
Prescription-required
EMA
Yes
Regulated as prescription drug
India
Available both OTC and RX
CDSCO
Prescription recommended
Varies by state
Australia
Prescription-only
TGA
Yes
Controlled medicine
Due to age-differences in plasma protein binding, the corresponding increase in the AUC of free (unbound) sildenafil and its activeN-desmethyl metabolite were 45% and 57%, respectively [ see Dosage and Administration (2.5),and Use in Specific Populations (8.5)]Renal Impairment:In volunteers with mild (CLcr=50 to 80 mL/min) and moderate (CLcr=30 to 49 mL/min) renal impairment, the pharmacokinetics of a single oral dose of sildenafil tablets (50 mg) were not altered.
Brand Name
Manufacturer
Dosage
Market Region
Price Range (USD)
Packaging Options
Viagra
Pfizer
50 mg
Global
10-20 per pill
Blister pack of 4-12 pills
Revatio
Pfizer
20 mg
Global
15-25 per pill
Blister pack of 30 pills
Kamagra
Ajanta Pharma
50 mg
India, SE Asia
2-5 per pill
Varies (blister)
Sildenafil Original
Local Pharmacies
50 mg
Local Markets
12-18 per pill
Bottle/Blister
In volunteers with severe (CLcr <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 [see Dosage and Administration (2.5),and Use in Specific Populations (8.6)].In addition, N-desmethyl metabolite AUC and C maxvalues significantly increased by 200% and 79%, respectively in subjects with severe renal impairment compared to subjects with normal renal function.Hepatic Impairment:In volunteers with hepatic impairment (Child-Pugh Class A and B), sildenafil clearance was reduced, resulting in increases in AUC (85%) and C max(47%) compared to age-matched volunteers with no hepatic impairment. The pharmacokinetics of sildenafil in patients with severely impaired hepatic function (Child-Pugh Class C) have not been studied [see Dosage and Administration (2.5), and Use in Specific Populations (8.7)].Therefore, age >65, hepatic impairment and severe renal impairment are associated with increased plasma levels of sildenafil. A starting oral dose of 25 mg should be considered in those patients [see Dosage and Administration (2.5)].Drug Interaction StudiesEffects of Other Drugs on Sildenafil TabletsSildenafil metabolism is principally mediated by CYP3A4 (major route) and CYP2C9 (minor route).
Sildenafil tablets may have different appearances depending on manufacturer. Consult a healthcare professional if unsure about dosing or interactions. Sildenafil should be used responsibly to prevent dependence. Some users experience a slight tingling sensation after ingestion. Generic sildenafil is usually less expensive but equally effective. Always buy from trusted sources to avoid counterfeit medication. Sildenafil can be used in combination with other ED treatments if advised. Certain medical conditions may contraindicate sildenafil use. The tablets are commonly available in blister packs for safety. Avoid combining sildenafil with grapefruit juice, which can affect metabolism. Keep a record of all medications and their effects during treatment.
Therefore, inhibitors of these isoenzymes may reduce sildenafil clearance and inducers of these isoenzymes may increase sildenafil clearance.
7.2 Alpha-blockers
Warnings for other groups
The concomitant use of erythromycin or strong CYP3A4 inhibitors (e.g., saquinavir, ketoconazole, itraconazole) as well as the nonspecific CYP inhibitor, cimetidine, is associated with increased plasma levels of sildenafil [see Dosage and Administration (2.4)].In vivostudies:Cimetidine (800 mg), a nonspecific CYP inhibitor, caused a 56% increase in plasma sildenafil concentrations when co-administered with sildenafil tablets (50 mg) to healthy volunteers.When a single 100 mg dose of sildenafil tablets were administered with erythromycin, a moderate CYP3A4 inhibitor, at steady state (500 mg bid for 5 days), there was a 160% increase in sildenafil C maxand a 182% increase in sildenafil AUC.
8.1 Pregnancy
In addition, in a study performed in healthy male volunteers, co-administration of the HIV protease inhibitor saquinavir, also a CYP3A4 inhibitor, at steady state (1200 mg tid) with sildenafil tablets (100 mg single dose) resulted in a 140% increase in sildenafil C maxand a 210% increase in sildenafil AUC.
What happens if women take Viagra?
A stronger CYP3A4 inhibitor such as ketoconazole or itraconazole could be expected to have greater effect than that seen with saquinavir. Population pharmacokinetic data from patients in clinical trials also indicated a reduction in sildenafil clearance when it was co- administered with CYP3A4 inhibitors (such as ketoconazole, erythromycin, or cimetidine) [see Dosage and Administration (2.4)and Drug Interactions (7.4)].In another study in healthy male volunteers, co-administration with the HIV protease inhibitor ritonavir, which is a highly potent P450 inhibitor, at steady state (500 mg bid) with sildenafil tablets (100 mg single dose) resulted in a 300% (4-fold) increase in sildenafil C maxand a 1000% (11-fold) increase in sildenafil plasma AUC. At 24 hours the plasma levels of sildenafil were still approximately 200 ng/mL, compared to approximately 5 ng/mL when sildenafil was dosed alone. This is consistent with ritonavir’s marked effects on a broad range of P450 substrates.
The legality of purchasing sildenafil varies by country. Online pharmacies may offer sildenafil, but verify their legitimacy. White sildenafil tablets are designed for rapid dissolution in the mouth or swallowing. Be aware of potential allergic reactions, such as rash or swelling. Avoid taking sildenafil with large meals that contain high fat content. The effectiveness of sildenafil depends on individual health conditions. The American Urological Association provides guidelines on sildenafil use. Sildenafil can cause safety concerns in patients with low blood pressure. The drug works best when taken approximately one hour before intimacy. Use sildenafil solely as directed; misuse can lead to health risks. Regular check-ups can help monitor the impact of sildenafil on health.
Sildenafil tablets had no effect on ritonavir pharmacokinetics [see Dosage and Administration (2.4)and Drug Interactions (7.4)].Although the interaction between other protease inhibitors and sildenafil has not been studied, their concomitant use is expected to increase sildenafil levels.In a study of healthy male volunteers, co-administration of sildenafil at steady state (80 mg t.i.d.) with endothelin receptor antagonist bosentan (a moderate inducer of CYP3A4, CYP2C9 and possibly of CYP2C19) at steady state (125 mg b.i.d.) resulted in a 63% decrease of sildenafil AUC and a 55% decrease in sildenafil C max.
