Sildenafil

Indications and Usage ( 1 ) 1/2023 Dosage and Administration ( Error! Hyperlink reference not valid. , 2.2) 1/2023

1 INDICATIONS AND USAGE Sildenafil tablets are indicated for the treatment of pulmonary arterial hypertension (WHO Group I) in adults to improve exercise ability and delay clinical worsening. The delay in clinical worsening was demonstrated when sildenafil tablets were added to background epoprostenol therapy [see Clinical Studies (14)] . Studies establishing effectiveness were short-term (12 to 16 weeks), and included predominately patients with New York Heart Association (NYHA) Functional Class II to III symptoms and idiopathic etiology (71%) or associated with connective tissue disease (CTD) (25%). Limitation of Use : Adding sildenafil to bosentan therapy does not result in any beneficial effect on exercise capacity [see Clinical Studies ( 14 )]. Sildenafil tablets are a phosphodiesterase-5 (PDE-5) inhibitor indicated for the treatment of pulmonary arterial hypertension (PAH) (WHO Group I) in adults to improve exercise ability and delay clinical worsening. Studies establishing effectiveness were short-term (12 to 16 weeks), and included predominately patients with NYHA Functional Class II to III symptoms. Etiologies were idiopathic (71%) or associated with connective tissue disease (25%). ( 1 ) Limitation of Use : Adding sildenafil to bosentan therapy does not result in any beneficial effect on exercise capacity. ( 1 , 14 )

2 DOSAGE AND ADMINISTRATION • For most patients, the recommended dose is 50 mg taken, as needed, approximately 1 hour before sexual activity. However, sildenafil tablets may be taken anywhere from 30 minutes to 4 hours before sexual activity ( 2.1 ) • Based on effectiveness and toleration, may increase to a maximum of 100 mg or decrease to 25 mg ( 2.1 ) • Maximum recommended dosing frequency is once per day ( 2.1 ) 2.1 Dosage Information For most patients, the recommended dose is 50 mg taken, as needed, approximately 1 hour before sexual activity. However, sildenafil tablets may be taken anywhere from 30 minutes to 4 hours before sexual activity. The maximum recommended dosing frequency is once per day. Based on effectiveness and toleration, the dose may be increased to a maximum recommended dose of 100 mg or decreased to 25 mg. 2.2 Use with Food Sildenafil tablets may be taken with or without food. 2.3 Dosage Adjustments in Specific Situations Sildenafil tablets were shown to potentiate the hypotensive effects of nitrates and their administration in patients who use nitric oxide donors such as organic nitrates or organic nitrites in any form is therefore contraindicated [ see Contraindications ( 4.1 ), Drug Interactions ( 7.1 ), and Clinical Pharmacology ( 12.2 ) ]. When sildenafil tablets are coadministered with an alpha-blocker, patients should be stable on alpha-blocker therapy prior to initiating sildenafil tablets treatment and sildenafil tablets should be initiated at 25 mg [ see Warnings and Precautions ( 5.5 ), Drug Interactions ( 7.2 ), and Clinical Pharmacology ( 12.2 ) ]. 2.4 Dosage Adjustments Due to Drug Interactions Ritonavir The recommended dose for ritonavir-treated patients is 25 mg prior to sexual activity and the recommended maximum dose is 25 mg within a 48 hour period because concomitant administration increased the blood levels of sildenafil by 11-fold [ see Warnings and Precautions ( 5.6 ), Drug Interactions ( 7.4 ), and Clinical Pharmacology ( 12.3 ) ]. CYP3A4 Inhibitors Consider a starting dose of 25 mg in patients treated with strong CYP3A4 inhibitors (e.g., ketoconazole, itraconazole, or saquinavir) or erythromycin. Clinical data have shown that coadministration with saquinavir or erythromycin increased plasma levels of sildenafil by about 3-fold [ see Drug Interactions ( 7.4 ) and Clinical Pharmacology ( 12.3 ) ]. 2.5 Dosage Adjustments in Special Populations Consider a starting dose of 25 mg in patients > 65 years, patients with hepatic impairment (e.g., cirrhosis), and patients with severe renal impairment (creatinine clearance < 30 mL/minute) because administration of sildenafil tablets in these patients resulted in higher plasma levels of sildenafil [ see Use in Specific Populations ( 8.5 , 8.6 , 8.7 ) and Clinical Pharmacology ( 12.3 ) ].

3 DOSAGE FORMS AND STRENGTHS Sildenafil Tablets USP, 25 mg are supplied as white to off white, oval shaped film-coated tablets containing sildenafil citrate, USP equivalent to 25 mg of sildenafil with debossing ‘AN 353’ on one side and plain on the other side. Sildenafil Tablets USP, 50 mg are supplied as white to off white, oval shaped film-coated tablets containing sildenafil citrate, USP equivalent to 50 mg of sildenafil with debossing ‘AN 354’ on one side and plain on the other side. Sildenafil Tablets USP, 100 mg are supplied as white to off white, oval shaped film-coated tablets containing sildenafil citrate, USP equivalent to 100 mg of sildenafil with debossing ‘AN 355’ on one side and plain on the other side. Tablets: 25 mg, 50 mg, 100 mg ( 3 )

4 CONTRAINDICATIONS 4. Administration of sildenafil tablets to patients using nitric oxide donors, such as organic nitrates or organic nitrites in any form. Sildenafil tablets were shown to potentiate the hypotensive effect of nitrates ( 4.1 , 7.1 , 12.2 ) 5. Known hypersensitivity to sildenafil or any component of tablet ( 4.2 ) 6. Administration with guanylate cyclase (GC) stimulators, such as riociguat ( 4.3 ) 4.1 Nitrates Consistent with its known effects on the nitric oxide/cGMP pathway [ see Clinical Pharmacology ( 12.1 , 12.2 ) ], sildenafil tablets were shown to potentiate the hypotensive effects of nitrates, and their administration to patients who are using nitric oxide donors such as organic nitrates or organic nitrites in any form either regularly and/or intermittently is therefore contraindicated. After patients have taken sildenafil tablets, it is unknown when nitrates, if necessary, can be safely administered. Although plasma levels of sildenafil at 24 hours post dose are much lower than at peak concentration, it is unknown whether nitrates can be safely coadministered at this time point [ see Dosage and Administration ( 2.3 ), Drug Interactions ( 7.1 ), and Clinical Pharmacology ( 12.2 ) ]. 4.2 Hypersensitivity Reactions Sildenafil tablets are contraindicated in patients with a known hypersensitivity to sildenafil, as contained in sildenafil tablets and REVATIO ® , or any component of the tablet. Hypersensitivity reactions have been reported, including rash and urticaria [ see Adverse Reactions ( 6.1 ) ]. 4.3 Concomitant Guanylate Cyclase (GC) Stimulators Do not use sildenafil tablets in patients who are using a GC stimulator, such as riociguat. PDE5 inhibitors, including sildenafil tablets, may potentiate the hypotensive effects of GC stimulators.

6 ADVERSE REACTIONS 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 Coadministered 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. Most common adverse reactions (≥ 2%) include headache, flushing, dyspepsia, abnormal vision, nasal congestion, back pain, myalgia, nausea, dizziness and rash ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Teva at 1-888-838-2872 or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch . 6.1 Clinical Trials Experience 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. Sildenafil was administered to over 3700 patients (aged 19 to 87 years) during premarketing clinical trials worldwide. Over 550 patients were treated for longer than one year. In placebo-controlled clinical studies, the discontinuation rate due to adverse reactions for sildenafil (2.5%) was not significantly different from placebo (2.3%). In fixed-dose studies, the incidence of some adverse reactions increased with dose. The type of adverse reactions in flexible-dose studies, which reflect the recommended dosage regimen, was similar to that for fixed-dose studies. At doses above the recommended dose range, adverse reactions were similar to those detailed in Table 1 below but generally were reported more frequently. Table 1: Adverse Reactions Reported by ≥ 2% of Patients Treated with Sildenafil and More Frequent than Placebo in Fixed-Dose Phase II/III Studies Adverse Reaction 25 mg (n = 312) 50 mg (n = 511) 100 mg (n = 506) Placebo (n = 607) Headache 16% 21% 28% 7% Flushing 10% 19% 18% 2% Dyspepsia 3% 9% 17% 2% Abnormal vision 1 1% 2% 11% 1% Nasal congestion 4% 4% 9% 2% Back pain 3% 4% 4% 2% Myalgia 2% 2% 4% 1% Nausea 2% 3% 3% 1% Dizziness 3% 4% 3% 2% Rash 1% 2% 3% 1% 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: Table 2. Adverse Reactions Reported by ≥ 2% of Patients Treated with Sildenafil and More Frequent than Placebo in Flexible-Dose Phase II/III Studies Adverse Reaction SILDENAFIL PLACEBO N = 734 N = 725 Headache 16% 4% Flushing 10% 1% Dyspepsia 7% 2% Nasal Congestion 4% 2% Abnormal Vision 1 3% 0% Back pain 2% 2% Dizziness 2% 1% Rash 2% 1% Abnormal Vision: Mild and transient, predominantly color tinge to vision, but also increased sensitivity to light or blurred vision. In these studies, only one patient discontinued due to abnormal vision. The following events occurred in < 2% of patients in controlled clinical trials; a causal relationship to sildenafil is uncertain. Reported events include those with a plausible relation to drug use; omitted are minor events and reports too imprecis …

7 DRUG INTERACTIONS • Sildenafil tablets can potentiate the hypotensive effects of nitrates, alpha blockers, and anti-hypertensives ( 4.1 , 5.5 , 7.1 , 7.2 , 7.3 , 12.2 ) • With concomitant use of alpha blockers, initiate sildenafil tablets at 25 mg dose ( 2.3 ) • CYP3A4 inhibitors (e.g., ritonavir, ketoconazole, itraconazole, erythromycin): Increase sildenafil tablets exposure ( 2.4 , 7.4 , 12.3 ) • Ritonavir: Do not exceed a maximum single dose of 25 mg in a 48 hour period ( 2.4 , 5.6 ) • Erythromycin or strong CYP3A4 inhibitors (e.g., ketoconazole, itraconazole, saquinavir): Consider a starting dose of 25 mg ( 2.4 , 7.4 ) 7.1 Nitrates Administration of sildenafil tablets 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 tablets were shown to potentiate the hypotensive effects of nitrates [see Dosage and Administration ( 2.3 ), Contraindications ( 4.1 ), Clinical Pharmacology ( 12.2 )]. 7.2 Alpha-blockers Use caution when co-administering alpha-blockers with sildenafil tablets because of potential additive blood pressure-lowering effects. When sildenafil tablets are co-administered with an alpha-blocker, patients should be stable on alpha-blocker therapy prior to initiating sildenafil tablets treatment and sildenafil tablets should be initiated at the lowest dose [see Dosage and Administration ( 2.3 ), Warnings and Precautions ( 5.5 ), Clinical Pharmacology ( 12.2 )]. 7.3 Amlodipine When sildenafil tablets 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 inhibitors 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 tablets 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 Cmax and AUC, respectively. Co-administration of saquinavir, a strong CYP3A4 inhibitor, resulted in 140% and 210% increases in sildenafil Cmax and AUC, respectively. Stronger CYP3A4 inhibitors such as ketoconazole or itraconazole could be expected to have greater effects than seen with saquinavir. A starting dose of 25 mg of sildenafil tablets 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 Alcohol 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 [see Clinical Pharmacology ( 12.2 )] .

8 USE IN SPECIFIC POPULATIONS 8.1 Pregnancy Risk Summary 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 the mother and fetus from untreated pulmonary arterial hypertension (see Clinical Considerations). Animal reproduction studies conducted with sildenafil showed no evidence of embryo-fetal toxicity or teratogenicity at doses up to 32- and 65-times the recommended human dose (RHD) of 20 mg three times a day in rats and rabbits, respectively (See Data). The estimated background risk of major birth defects and miscarriage for the indicated population is unknown. All pregnancies have a background risk of birth defect, loss, or other adverse outcomes. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2 to 4% and 15 to 20%, respectively. Clinical Considerations Disease-Associated Maternal and/or Embryo/Fetal Risk Pregnant women with untreated pulmonary arterial hypertension are at risk for heart failure, stroke, preterm delivery, and maternal and fetal death. Data Animal Data No evidence of teratogenicity, embryotoxicity, or fetotoxicity was observed in pregnant rats or rabbits dosed with sildenafil 200 mg/kg/day during organogenesis, a level that is, on a mg/m 2 basis, 32- and 65-times, respectively, the recommended human dose (RHD)20 mg three times a day. In a rat pre- and postnatal development study, the no-observed-adverse-effect dose was 30 mg/kg/day (equivalent to 5-times the RHD on a mg/m 2 basis). 8.2 Lactation Risk summary Limited published data from a case report describe the presence of sildenafil and its active metabolite in human milk. There is insufficient information about the effects of sildenafil on the breastfed infant and no information on the effects of sildenafil on milk production. Limited clinical data during lactation preclude a clear determination of the risk of sildenafil to an infant during lactation. 8.4 Pediatric Use In a randomized, double-blind, multi-center, placebo-controlled, parallel-group, dose-ranging study, 234 patients with PAH, aged 1 to 17 years, body weight greater than or equal to 8 kg, were randomized, on the basis of body weight, to three dose levels of sildenafil tablets, or placebo, for 16 weeks of treatment. Most patients had mild to moderate symptoms at baseline: WHO Functional Class I (32%), II (51%), III (15%), or IV (0.4%). One-third of patients had primary PAH; two-thirds had secondary PAH (systemic-to-pulmonary shunt in 37%; surgical repair in 30%). Sixty-two percent of patients were female. Drug or placebo was administered three times a day. The primary objective of the study was to assess the effect of sildenafil tablets on exercise capacity as measured by cardiopulmonary exercise testing in pediatric patients developmentally able to perform the test (n = 115). Administration of sildenafil tablets did not result in a statistically significant improvement in exercise capacity in those patients. No patients died during the 16-week controlled study. After completing the 16-week controlled study, a patient originally randomized to sildenafil tablets remained on his/her dose of sildenafil tablets or, if originally randomized to placebo, was randomized to low-, medium-, or high-dose sildenafil tablets. After all patients completed 16 weeks of follow-up in the controlled study, the blind was broken and doses were adjusted as clinically indicated. Patients treated with sildenafil were followed for a median of 4.6 years (range 2 days to 8.6 years). Mortality during the long-term study, by originally assigned dose, is shown in Figure 6: Figure 6: Kaplan-Meier Plot of Mortality by Sildenafil Tablets Dose During the study, there were 42 reported deaths, with 37 of t …

12.1 Mechanism of Action The physiologic mechanism of erection of the penis involves release of nitric oxide (NO) in the corpus cavernosum during sexual stimulation. NO then activates the enzyme guanylate cyclase, which results in increased levels of cyclic guanosine monophosphate (cGMP), producing smooth muscle relaxation in the corpus cavernosum and allowing inflow of blood. Sildenafil enhances the effect of NO by inhibiting phosphodiesterase type 5 (PDE5), which is responsible for degradation of cGMP in the corpus cavernosum. Sildenafil has no direct relaxant effect on isolated human corpus cavernosum. When sexual stimulation causes local release of NO, inhibition of PDE5 by sildenafil causes increased levels of cGMP in the corpus cavernosum, resulting in smooth muscle relaxation and inflow of blood to the corpus cavernosum. Sildenafil at recommended doses has no effect in the absence of sexual stimulation. Binding Characteristics Studies in vitro have shown that sildenafil is selective for PDE5. Its effect is more potent on PDE5 than on other known phosphodiesterases (10-fold for PDE6, > 80-fold for PDE1, > 700-fold for PDE2, PDE3, PDE4, PDE7, PDE8, PDE9, PDE10, and PDE11). Sildenafil is approximately 4,000-fold more selective for PDE5 compared to PDE3. PDE3 is involved in control of cardiac contractility. Sildenafil is only about 10-fold as potent for PDE5 compared to PDE6, an enzyme found in the retina which is involved in the phototransduction pathway of the retina. This lower selectivity is thought to be the basis for abnormalities related to color vision [ see Clinical Pharmacology ( 12.2 ) ]. In addition to human corpus cavernosum smooth muscle, PDE5 is also found in other tissues including platelets, vascular and visceral smooth muscle, and skeletal muscle, brain, heart, liver, kidney, lung, pancreas, prostate, bladder, testis, and seminal vesicle. The inhibition of PDE5 in some of these tissues by sildenafil may be the basis for the enhanced platelet antiaggregatory activity of NO observed in vitro , an inhibition of platelet thrombus formation in vivo and peripheral arterial-venous dilatation in vivo .

11 DESCRIPTION Sildenafil, phosphodiesterase-5 (PDE-5) inhibitor, is the citrate salt of sildenafil, a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type-5 (PDE- 5). Sildenafil is also marketed as VIAGRA ® for erectile dysfunction. Sildenafil citrate is designated chemically as 1-[[3-(6,7-dihydro-1-methyl-7-oxo-3-propyl-1 H - pyrazolo [4,3- d ] pyrimidin-5-yl)-4-ethoxyphenyl] sulfonyl]-4-methylpiperazine citrate and has the following structural formula: Sildenafil citrate is a white to off-white crystalline powder with a solubility of 3.5 mg/mL in water and a molecular weight of 666.7. Sildenafil Tablets, USP are formulated as blue colored, round, film-coated tablets for oral administration. Each tablet contains sildenafil citrate equivalent to 20 mg of sildenafil. In addition to the active ingredient, sildenafil citrate, each tablet contains the following inactive ingredients: croscarmellose sodium, dibasic calcium phosphate dihydrate, hydroxypropyl cellulose, magnesium stearate, microcrystalline cellulose, and blue film coating containing hydroxypropylmethyl cellulose, lactose monohydrate, titanium dioxide, triacetin, glycerol triacetate, FD&C Blue # 2, Indigotine aluminum lake. image description

10 OVERDOSAGE In studies with healthy volunteers of single doses up to 800 mg, adverse reactions were similar to those seen at lower doses but incidence rates and severities were increased. In cases of overdose, standard supportive measures should be adopted as required. Renal dialysis is not expected to accelerate clearance as sildenafil is highly bound to plasma proteins and it is not eliminated in the urine.

16 HOW SUPPLIED/STORAGE AND HANDLING Sildenafil tablets, USP are supplied as: 25 mg Tablets: White, oval shaped, biconvex, film coated tablets, plain on one side and debossed with 'B9' on the other side. Bottle of 30 Tablets with child-resistant closure NDC 59746-434-30 Bottle of 90 Tablets with child-resistant closure NDC 59746-434-90 Bottle of 500 Tablets NDC 59746-434-05 100 Unit-dose Tablets (10 x 10) NDC 59746-434-03 50 mg Tablets: White, oval shaped, biconvex, film coated tablets, plain on one side and debossed with 'C1' on the other side. Bottle of 30 Tablets with child-resistant closure NDC 59746-435-30 Bottle of 90 Tablets with child-resistant closure NDC 59746-435-90 Bottle of 100 Tablets with child-resistant closure NDC 59746-435-01 Bottle of 500 Tablets NDC 59746-435-05 100 Unit-dose Tablets (10 x 10) NDC 59746-435-03 100 mg Tablets: White, oval shaped, biconvex, film coated tablets, plain on one side and debossed with '436' on the other side. Bottle of 30 Tablets with child-resistant closure NDC 59746-436-30 Bottle of 90 Tablets with child-resistant closure NDC 59746-436-90 Bottle of 100 Tablets with child-resistant closure NDC 59746-436-01 Bottle of 500 Tablets NDC 59746-436-05 100 Unit-dose Tablets (10 x 10) NDC 59746-436-03 Recommended Storage: Store at 20°C to 25°C (68°F to 77°F); excursions permitted between 15°C to 30°C (59°F to 86°F) [See USP Controlled Room Temperature] .