13 NONCLINICAL TOXICOLOGY
It is not possible to determine whether these reported events are related directly to the use of sildenafil, to the patient’s underlying risk factors for hearing loss, a combination of these factors, or to other factors [ see Warnings and Precautions (5.4)and Patient Counseling Information (17)].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.Non-arteritic anterior ischemic optic neuropathy (NAION), a cause of decreased vision including permanent loss of vision, has been reported rarely post-marketing in temporal association with the use of phosphodiesterase type 5 (PDE5) inhibitors, including sildenafil.
- Sildenafil citrate 100 mg should be taken approximately 30-60 minutes before sexual activity.
- Avoid taking sildenafil with a high-fat meal, as it may delay absorption.
- Do not exceed one dose in 24 hours to reduce risk of side effects.
Most, but not all, of these patients had underlying anatomic or vascular risk factors for developing NAION, including but not necessarily limited to: low cup to disc ratio (“crowded disc”), age over 50, diabetes, hypertension, coronary artery disease, hyperlipidemia and smoking [ see Warnings and Precautions (5.3)and Patient Counseling Information (17)].Urogenital:prolonged erection, priapism [ see Warnings and Precautions (5.2) andPatient Counseling Information (17)], and hematuria. The following are discussed in more detail in other sections of the labeling: Cardiovascular [ see Warnings and Precautions (5.1)] Prolonged Erection and Priapism [ see Warnings and Precautions (5.2)] Effects on the Eye [ see Warnings and Precautions (5.3)] Hearing Loss [ see Warnings and Precautions (5.4)] Hypotension when Co-administered with Alpha-blockers or Anti-hypertensives [ see Warnings and Precautions (5.5)] Adverse Reactions with the Concomitant Use of Ritonavir [ see Warnings and Precautions (5.6)] Combination with other PDE5 Inhibitors or Other Erectile Dysfunction Therapies [ see Warnings and Precautions (5.7)] Effects on Bleeding [ see Warnings and Precautions (5.8)] Counseling Patients About Sexually Transmitted Diseases [ see Warnings and Precautions (5.9)] The most common adverse reactions reported in clinical trials (≥ 2%) are headache, flushing, dyspepsia, abnormal vision, nasal congestion, back pain, myalgia, nausea, dizziness, and rash. Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in clinical practice.
Dosage And Administration
It is not possible to determine whether these reported events are related directly to the use of sildenafil, to the patient’s underlying risk factors for hearing loss, a combination of these factors, or to other factors [ see Warnings and Precautions (5.4)and Patient Counseling Information (17)].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.Non-arteritic anterior ischemic optic neuropathy (NAION), a cause of decreased vision including permanent loss of vision, has been reported rarely post-marketing in temporal association with the use of phosphodiesterase type 5 (PDE5) inhibitors, including sildenafil. Most, but not all, of these patients had underlying anatomic or vascular risk factors for developing NAION, including but not necessarily limited to: low cup to disc ratio (“crowded disc”), age over 50, diabetes, hypertension, coronary artery disease, hyperlipidemia and smoking [ see Warnings and Precautions (5.3)and Patient Counseling Information (17)].Urogenital:prolonged erection, priapism [ see Warnings and Precautions (5.2) andPatient Counseling Information (17)], and hematuria. The following are discussed in more detail in other sections of the labeling: Cardiovascular [ see Warnings and Precautions (5.1)] Prolonged Erection and Priapism [ see Warnings and Precautions (5.2)] Effects on the Eye [ see Warnings and Precautions (5.3)] Hearing Loss [ see Warnings and Precautions (5.4)] Hypotension when Co-administered with Alpha-blockers or Anti-hypertensives [ see Warnings and Precautions (5.5)] Adverse Reactions with the Concomitant Use of Ritonavir [ see Warnings and Precautions (5.6)] Combination with other PDE5 Inhibitors or Other Erectile Dysfunction Therapies [ see Warnings and Precautions (5.7)] Effects on Bleeding [ see Warnings and Precautions (5.8)] Counseling Patients About Sexually Transmitted Diseases [ see Warnings and Precautions (5.9)] The most common adverse reactions reported in clinical trials (≥ 2%) are headache, flushing, dyspepsia, abnormal vision, nasal congestion, back pain, myalgia, nausea, dizziness, and rash. Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in clinical practice. Table 1: Adverse Reactions Reported by ≥2% of Patients Treated with sildenafil and More Frequent than Placebo in Fixed-Dose Phase II/III Studies † Abnormal Vision: Mild to moderate in severity and transient, predominantly color tinge to vision, but also increased sensitivity to light, or blurred vision.
Vitamin K Antagonists
When sildenafil was taken as recommended (on an as-needed basis) in flexible-dose, placebo-controlled clinical trials of two to twenty-six weeks duration, patients took sildenafil at least once weekly, and the following adverse reactions were reported: Adverse Reactions Reported by ≥2% of Patients Treated with sildenafil and More Frequent than Placebo in Flexible-Dose Phase II/III Studies Body as a Whole:face edema, photosensitivity reaction, shock, asthenia, pain, chills, accidental fall, abdominal pain, allergic reaction, chest pain, accidental injury. The following adverse reactions have been identified during post approval use of sildenafil . These events have been chosen for inclusion either due to their seriousness, reporting frequency, lack of clear alternative causation, or a combination of these factors. 7 DRUG INTERACTIONS 7.1 NitratesAdministration of sildenafil with nitric oxide donors such as organic nitrates or organic nitrites in any form is contraindicated. Consistent with its known effects on the nitric oxide/cGMP pathway, sildenafil was shown to potentiate the hypotensive effects of nitrates [ seeDosage and Administration (2.3),Contraindications (4.1),Clinical Pharmacology (12.2)].7.2 Alpha-blockersUse caution when co-administering alpha-blockers with sildenafil because of potential additive blood pressure-lowering effects.
Platelet-aggregation Inhibitors
When sildenafil is co-administered with an alpha-blocker, patients should be stable on alpha-blocker therapy prior to initiating sildenafil treatment and sildenafil should be initiated at the lowest dose [ see Dosage and Administration (2.3), Warnings and Precautions (5.5), Clinical Pharmacology (12.2)].7.3 AmlodipineWhen sildenafil 100 mg was co-administered with amlodipine (5 mg or 10 mg) to hypertensive patients, the mean additional reduction on supine blood pressure was 8 mmHg systolic and 7 mmHg diastolic [ see Warnings and Precautions (5.5), Clinical Pharmacology (12.2)].7.4 Ritonavir and other CYP3A4 inhibitorsCo-administration of ritonavir, a strong CYP3A4 inhibitor, greatly increased the systemic exposure of sildenafil (11-fold increase in AUC). It is therefore recommended not to exceed a maximum single dose of 25 mg of sildenafil in a 48 hour period [ see Dosage and Administration (2.4), Warnings and Precautions (5.6), Clinical Pharmacology (12.3)].Co-administration of erythromycin, a moderate CYP3A4 inhibitor, resulted in a 160% and 182% increases in sildenafil C maxand AUC, respectively. Co-administration of saquinavir, a strong CYP3A4 inhibitor, resulted in 140% and 210% increases in sildenafil C maxand AUC, respectively. Stronger CYP3A4 inhibitors such as ketoconazole or itraconazole could be expected to have greater effects than sildenafil citrate 100mg tablets seen with saquinavir. A starting dose of 25 mg of sildenafil should be considered in patients taking erythromycin or strong CYP3A4 inhibitors (such as saquinavir, ketoconazole, itraconazole) [ see Dosage and Administration (2.4), Clinical Pharmacology (12.3)].7.5 AlcoholIn a drug-drug interaction study sildenafil 50 mg given with alcohol 0.5 g/kg in which mean maximum blood alcohol levels of 0.08% was achieved, sildenafil did not potentiate the hypotensive effect of alcohol in healthy volunteers [ seeClinical Pharmacology (12.2)]. Table 1: Adverse Reactions Reported by ≥2% of Patients Treated with sildenafil and More Frequent than Placebo in Fixed-Dose Phase II/III Studies † Abnormal Vision: Mild to moderate in severity and transient, predominantly color tinge to vision, but also increased sensitivity to light, or blurred vision. When sildenafil was taken as recommended (on an as-needed basis) in flexible-dose, placebo-controlled clinical trials of two to twenty-six weeks duration, patients took sildenafil at least once weekly, and the following adverse reactions were reported: Adverse Reactions Reported by ≥2% of Patients Treated with sildenafil and More Frequent than Placebo in Flexible-Dose Phase II/III Studies Body as a Whole:face edema, photosensitivity reaction, shock, asthenia, pain, chills, accidental fall, abdominal pain, allergic reaction, chest pain, accidental injury. The following adverse reactions have been identified during post approval use of sildenafil .
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These events have been chosen for inclusion either due to their seriousness, reporting frequency, lack of clear alternative causation, or a combination of these factors. 7 DRUG INTERACTIONS 7.1 NitratesAdministration of sildenafil with nitric oxide donors such as organic nitrates or organic nitrites in any form is contraindicated. Consistent with its known effects on the nitric oxide/cGMP pathway, sildenafil was shown to potentiate the hypotensive effects of nitrates [ seeDosage and Administration (2.3),Contraindications (4.1),Clinical Pharmacology (12.2)].7.2 Alpha-blockersUse caution when co-administering alpha-blockers with sildenafil because of potential additive blood pressure-lowering effects.
2.3 Dosage Adjustments in Specific Situations
No overall differences in safety or efficacy were observed between older (≥ 65 years of age) and younger (< 65 years of age) subjects.However, since higher plasma levels may increase the incidence of adverse reactions, a starting dose of 25 mg should be considered in older subjects due to the higher systemic exposure [ see Dosage and Administration (2.5)].8.6 Renal ImpairmentNo dose adjustment is required for mild (CLcr=50-80 mL/min) and moderate (CLcr=30-49 mL/min) renal impairment.
Special Populations
When sildenafil is co-administered with an alpha-blocker, patients should be stable on alpha-blocker therapy prior to initiating sildenafil treatment and sildenafil should be initiated at the lowest dose [ see Dosage and Administration (2.3), Warnings and Precautions (5.5), Clinical Pharmacology (12.2)].7.3 AmlodipineWhen sildenafil 100 mg was co-administered with amlodipine (5 mg or 10 mg) to hypertensive patients, the mean additional reduction on supine blood pressure was 8 mmHg systolic and 7 mmHg diastolic [ see Warnings and Precautions (5.5), Clinical Pharmacology (12.2)].7.4 Ritonavir and other CYP3A4 inhibitorsCo-administration of ritonavir, a strong CYP3A4 inhibitor, greatly increased the systemic exposure of sildenafil (11-fold increase in AUC). It is therefore recommended not to exceed a maximum single dose of 25 mg of sildenafil in a 48 hour period [ see Dosage and Administration (2.4), Warnings and Precautions (5.6), Clinical Pharmacology (12.3)].Co-administration of erythromycin, a moderate CYP3A4 inhibitor, resulted in a 160% and 182% increases in sildenafil C maxand AUC, respectively. Co-administration of saquinavir, a strong CYP3A4 inhibitor, resulted in 140% and 210% increases in sildenafil C maxand AUC, respectively. Stronger CYP3A4 inhibitors such as ketoconazole or itraconazole could be expected to have greater effects than sildenafil citrate 100mg tablets seen with saquinavir.
- Sildenafil 100 mg can be used for pulmonary arterial hypertension in some cases.
- It is not intended for use in women or children.
- Regular use of sildenafil does not cure erectile dysfunction but manages symptoms.
A starting dose of 25 mg of sildenafil should be considered in patients taking erythromycin or strong CYP3A4 inhibitors (such as saquinavir, ketoconazole, itraconazole) [ see Dosage and Administration (2.4), Clinical Pharmacology (12.3)].7.5 AlcoholIn a drug-drug interaction study sildenafil 50 mg given with alcohol 0.5 g/kg in which mean maximum blood alcohol levels of 0.08% was achieved, sildenafil did not potentiate the hypotensive effect of alcohol in healthy volunteers [ seeClinical Pharmacology (12.2)].
Ethics declarations
Administration of sildenafil with nitric oxide donors such as organic nitrates or organic nitrites in any form is contraindicated. Consistent with its known effects on the nitric oxide/cGMP pathway, sildenafil was shown to potentiate the hypotensive effects of nitrates [ seeDosage and Administration (2.3),Contraindications (4.1),Clinical Pharmacology (12.2)]. Use caution when co-administering alpha-blockers with sildenafil because of potential additive blood pressure-lowering effects. When sildenafil is co-administered with an alpha-blocker, patients should be stable on alpha-blocker therapy prior to initiating sildenafil treatment and sildenafil should be initiated at the lowest dose [ see Dosage and Administration (2.3), Warnings and Precautions (5.5), Clinical Pharmacology (12.2)]. When sildenafil 100 mg was co-administered with amlodipine (5 mg or 10 mg) to hypertensive patients, the mean additional reduction on supine blood pressure was 8 mmHg systolic and 7 mmHg diastolic [ see Warnings and Precautions (5.5), Clinical Pharmacology (12.2)].
Sildenafil side effects
Co-administration of ritonavir, a strong CYP3A4 inhibitor, greatly increased the systemic exposure of sildenafil (11-fold increase in AUC). It is therefore recommended not to exceed a maximum single dose of 25 mg of sildenafil in a 48 hour period [ see Dosage and Administration (2.4), Warnings and Precautions (5.6), Clinical Pharmacology (12.3)]. In a drug-drug interaction study sildenafil 50 mg given with alcohol 0.5 g/kg in which mean maximum blood alcohol levels of 0.08% was achieved, sildenafil did not potentiate the hypotensive effect of alcohol in healthy volunteers [ seeClinical Pharmacology (12.2)]. 8 USE IN SPECIFIC POPULATIONS 8.1 PregnancyRisk SummarySildenafil is not indicated for use in females.There are no data with the use of sildenafil in pregnant women to inform any drug-associated risks for adverse developmental outcomes. Animal reproduction studies conducted with sildenafil did not show adverse developmental outcomes when administered during organogenesis in rats and rabbits at oral doses up to 16 and 32 times, respectively, the maximum recommended human dose (MRHD) of 100 mg/day on a mg/m 2basis ( see Data).DataAnimal DataNo evidence of teratogenicity, embryotoxicity or fetotoxicity was observed in rats and rabbits which received oral doses up to 200 mg/kg/day during organogenesis.
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These doses represent, respectively, about 16 and 32 times the MRHD on a mg/m 2basis in a 50 kg subject. In the rat pre- and postnatal development study, the no observed adverse effect dose was 30 mg/kg/day given for 36 days, about 2 times the MRHD on a mg/m 2basis in a 50 kg subject.8.2 LactationRisk SummarySildenafil is not indicated for use in females.Limited data indicate that sildenafil and its active metabolite are present in human milk. There is no information on the effects on the breastfed child, or the effects on milk production.8.4 Pediatric UseSildenafil is not indicated for use in pediatric patients. Safety and effectiveness have not been established in pediatric patients.8.5 Geriatric UseHealthy 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 young volunteers (18-45 years) [ see Clinical Pharmacology (12.3)]. 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 [ seeClinical Pharmacology (12.3)].Of the total number of subjects in clinical studies of sildenafil, 18% were 65 years and older, while 2% were 75 years and older. Administration of sildenafil with nitric oxide donors such as organic nitrates or organic nitrites in any form is contraindicated. Consistent with its known effects on the nitric oxide/cGMP pathway, sildenafil was shown to potentiate the hypotensive effects of nitrates [ seeDosage and Administration (2.3),Contraindications (4.1),Clinical Pharmacology (12.2)]. Use caution when co-administering alpha-blockers with sildenafil because of potential additive blood pressure-lowering effects. When sildenafil is co-administered with an alpha-blocker, patients should be stable on alpha-blocker therapy prior to initiating sildenafil treatment and sildenafil should be initiated at the lowest dose [ see Dosage and Administration (2.3), Warnings and Precautions (5.5), Clinical Pharmacology (12.2)].
| Monitoring Aspect | Purpose | Key Metrics |
|---|---|---|
| Adverse Event Reporting | Track side effects and adverse reactions | Unexpected or severe reactions |
| Cardiac Function Monitoring | Patients with cardiovascular risk | ECG or other assessments |
| Liver and Kidney Function Tests | Patients on long-term therapy | Ensure no organ damage |
| Patient Education | Inform about common side effects and interaction risks | Enhance safe usage |
When sildenafil 100 mg was co-administered with amlodipine (5 mg or 10 mg) to hypertensive patients, the mean additional reduction on supine blood pressure was 8 mmHg systolic and 7 mmHg diastolic [ see Warnings and Precautions (5.5), Clinical Pharmacology (12.2)]. Co-administration of ritonavir, a strong CYP3A4 inhibitor, greatly increased the systemic exposure of sildenafil (11-fold increase in AUC). It is therefore recommended not to exceed a maximum single dose of 25 mg of sildenafil in a 48 hour period [ see Dosage and Administration (2.4), Warnings and Precautions (5.6), Clinical Pharmacology (12.3)]. In a drug-drug interaction study sildenafil 50 mg given with alcohol 0.5 g/kg in which mean maximum blood alcohol levels of 0.08% was achieved, sildenafil did not potentiate the hypotensive effect of alcohol in healthy volunteers [ seeClinical Pharmacology (12.2)]. 8 USE IN SPECIFIC POPULATIONS 8.1 PregnancyRisk SummarySildenafil is not indicated for use in females.There are no data with the use of sildenafil in pregnant women to inform any drug-associated risks for adverse developmental outcomes.
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Animal reproduction studies conducted with sildenafil did not show adverse developmental outcomes when administered during organogenesis in rats and rabbits at oral doses up to 16 and 32 times, respectively, the maximum recommended human dose (MRHD) of 100 mg/day on a mg/m 2basis ( see Data).DataAnimal DataNo evidence of teratogenicity, embryotoxicity or fetotoxicity was observed in rats and rabbits which received oral doses up to 200 mg/kg/day during organogenesis. These doses represent, respectively, about 16 and 32 times the MRHD on a mg/m 2basis in a 50 kg subject. In the rat pre- and postnatal development study, the no observed adverse effect dose was 30 mg/kg/day given for 36 days, about 2 times the MRHD on a mg/m 2basis in a 50 kg subject.8.2 LactationRisk SummarySildenafil is not indicated for use in females.Limited data indicate that sildenafil and its active metabolite are present in human milk.
- People with heart problems should consult a doctor before using sildenafil 100 mg.
- Sildenafil is contraindicated in patients with severe liver or kidney impairment.
- Allergic reactions, though rare, may include rash, itching, or swelling.
There is no information on the effects on the breastfed child, or the effects on milk production.8.4 Pediatric UseSildenafil is not indicated for use in pediatric patients. Safety and effectiveness have not been established in pediatric patients.8.5 Geriatric UseHealthy 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 young volunteers (18-45 years) [ see Clinical Pharmacology (12.3)].
| Property | Description | Typical Dose | Onset Time | Duration of Action |
|---|---|---|---|---|
| Mechanism of Action | PDE5 inhibitor that enhances blood flow to the penis | 100 mg | 30-60 min | 4-6 hours |
| Bioavailability | Percentage of drug reaching systemic circulation | ~40% | N/A | N/A |
| Half-life | Time for plasma concentration to reduce by half | 4 hours | N/A | N/A |
| Metabolism | Liver enzymes involved (primarily CYP3A4) | CYP3A4 | N/A | N/A |
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 [ seeClinical Pharmacology (12.3)].Of the total number of subjects in clinical studies of sildenafil, 18% were 65 years and older, while 2% were 75 years and older. No overall differences in safety or efficacy were observed between older (≥ 65 years of age) and younger (< 65 years of age) subjects.However, since higher plasma levels may increase the incidence of adverse reactions, a starting dose of 25 mg should be considered in older subjects due to the higher systemic exposure [ see Dosage and Administration (2.5)].8.6 Renal ImpairmentNo dose adjustment is required for mild (CLcr=50-80 mL/min) and moderate (CLcr=30-49 mL/min) renal impairment.
| Side Effect | Frequency | Severity | Advice |
|---|---|---|---|
| Headache | Very common | Mild to moderate | Hydration, symptomatic relief |
| Flushing | Common | Mild | Cool environment |
| Nasal Congestion | Common | Mild | Use nasal decongestants |
| Dizziness | Less common | Mild to moderate | Avoid driving until normal |
