Sildenafil - Pfizer

Based on published literature, the annual incidence of NAION is 2.5-11.8 cases per 100,000 males aged ≥ 50 per year in the general population. An observational study evaluated whether recent, episodic use of PDE5 inhibitors (as a class), typical of erectile dysfunction treatment, was associated with acute onset of NAION. The results suggest an approximately 2-fold increase in the risk of NAION within 5 half-lives of PDE5 inhibitor use. It is not possible to determine whether these events are related directly to the use of PDE-5 inhibitors, to the patient’s underlying vascular risk factors or anatomical defects, to a combination of these factors, or to other factors. Advise patients to seek immediate medical attention in the event of a sudden loss of vision in one or both eyes while taking PDE-5 inhibitors, including sildenafil citrate. Physicians should also discuss the increased risk of NAION with patients who have already experienced NAION in one eye, including whether such individuals could be adversely affected by use of vasodilators, such as PDE-5 inhibitors.

Property	Description	Value	Units
Molecular Weight	The mass of one mole of sildenafil citrate	474.58	g/mol
Chemical Formula	Molecular composition	C22H30N6O4S
Solubility	Water solubility	Slightly soluble	at 25°C
pH of Solution	Typical pH when dissolved in water	3.8 - 4.2
Melting Point	The temperature at which it melts	196 - 198	°C

There are no controlled clinical data on the safety or efficacy of sildenafil citrate in patients with retinitis pigmentosa, a minority whom have genetic disorders of retinal phosphodiesterases. Prescribe sildenafil citrate with caution in these patients.

Warnings & Precautions

After completing the 16-week controlled study, a patient originally randomized to sildenafil citrate remained on his/her dose of sildenafil citrate or, if originally randomized to placebo, was randomized to low-, medium-, or high-dose sildenafil citrate. After all patients completed 16 weeks of follow-up in the controlled study, the blind was broken and doses were adjusted as clinically indicated. Cases of sudden decrease or loss of hearing, which may be accompanied by tinnitus and dizziness, have been reported in temporal association with the use of PDE-5 inhibitors, including sildenafil citrate. In some of the cases, medical conditions and other factors were reported that may have played a role. In many cases, medical follow-up information was limited. It is not possible to determine whether these reported events are related directly to the use of sildenafil citrate, to the patient’s underlying risk factors for hearing loss, a combination of these factors, or to other factors. Advise patients to seek prompt medical attention in the event of sudden decrease or loss of hearing while taking PDE-5 inhibitors, including sildenafil citrate. Sildenafil is also marketed as Sildenafil citrate®. The safety and efficacy of combinations of sildenafil citrate with Sildenafil citrate or other PDE-5 inhibitors have not been studied. Inform patients taking sildenafil citrate not to take Sildenafil citrate or other PDE5 inhibitors.

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In the event of an erection that persists longer than 4 hours, the patient should seek immediate medical assistance.

Use in Specific Populations

When sildenafil 100 mg oral was co-administered with amlodipine, 5 mg or 10 mg oral, to hypertensive patients, the mean additional reduction on supine blood pressure was 8 mmHg systolic and 7 mmHg diastolic. There are no adequate and well-controlled studies of sildenafil in pregnant women. 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/m2 basis, 32- and 68-times, respectively, the recommended human dose (RHD) of 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/m2 basis). Pregnancy Category (AUS): There is no Australian Drug Evaluation Committee (ADEC) guidance on usage of Sildenafil in women who are pregnant.

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The safety and efficacy of sildenafil citrate during labor and delivery has not been studied. It is not known if sildenafil or its metabolites are excreted in human breast milk. Because many drugs are excreted in human milk, caution should be exercised when sildenafil citrate is administered to a nursing woman. 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 citrate, 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%).

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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. The primary objective of the study was to assess the effect of sildenafil citrate on exercise capacity as measured by cardiopulmonary exercise testing in pediatric patients developmentally able to perform the test (n = 115). Administration of sildenafil citrate did not result in a statistically significant improvement in exercise capacity in those patients. No patients died during the 16-week controlled study. If priapism (painful erection greater than 6 hours in duration) is not treated immediately, penile tissue damage and permanent loss of potency could result.

How Sildenafil Works

In a placebo-controlled fixed dose titration study (Study 2) of sildenafil citrate (starting with recommended dose of 20 mg TID and increased to 40 mg TID and then 80 mg TID) as an adjunct to intravenous epoprostenol in patients with PAH, the adverse reactions that were more frequent in the sildenafil citrate + epoprostenol group than in the epoprostenol group (greater than 6% difference) are shown in Table 2 . The following adverse reactions have been identified during post approval use of * Sildenafil (marketed for both PAH and erectile dysfunction). Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. In postmarketing experience with sildenafil at doses indicated for erectile dysfunction, serious cardiovascular, cerebrovascular, and vascular events, including myocardial infarction, sudden cardiac death, ventricular arrhythmia, cerebrovascular hemorrhage, transient ischemic attack, hypertension, pulmonary hemorrhage, and subarachnoid and intracerebral hemorrhages have been reported in temporal association with the use of the drug. Most, but not all, of these patients had preexisting cardiovascular risk factors.

How can I tell if Viagra’s not working?

Many of these events were reported to occur during or shortly after sexual activity, and a few were reported to occur shortly after the use of sildenafil without sexual activity. Others were reported to have occurred hours to days after use concurrent with sexual activity. It is not possible to determine whether these events are related directly to sildenafil, to sexual activity, to the patient’s underlying cardiovascular disease, or to a combination of these or other factors. Concomitant use of sildenafil citrate with nitrates in any form is contraindicated. Concomitant use of sildenafil citrate with ritonavir and other potent CYP3A inhibitors is not recommended.

Dosage Forms & Strengths

In drug-drug interaction studies, sildenafil (25 mg, 50 mg, or 100 mg) and the alpha-blocker doxazosin (4 mg or 8 mg) were administered simultaneously to patients with benign prostatic hyperplasia (BPH) stabilized on doxazosin therapy. In these study populations, mean additional reductions of supine systolic and diastolic blood pressure of 7/7 mmHg, 9/5 mmHg, and 8/4 mmHg, respectively, were observed. Mean additional reductions of standing blood pressure of 6/6 mmHg, 11/4 mmHg, and 4/5 mmHg, respectively, were also observed. There were infrequent reports of patients who experienced symptomatic postural hypotension. These reports included dizziness and light-headedness, but not syncope. In a small, prematurely terminated study of patients with pulmonary hypertension (PH) secondary to sickle cell disease, vaso-occlusive crises requiring hospitalization were more commonly reported by patients who received sildenafil citrate than by those randomized to placebo.

• Sildenafil citrate is manufactured by several pharmaceutical companies.
• Its chemical formula is C22H30N6O4S.
• It has a half-life of approximately 4 hours in the body.
• The drug enhances nitric oxide activity in the corpus cavernosum.
• It’s important to follow prescribed dosing to avoid adverse effects.
• It is classified as a phosphodiesterase type 5 inhibitor.
• Sildenafil was initially researched for angina before ED use.

The effectiveness and safety of sildenafil citrate in the treatment of PAH secondary to sickle cell anemia has not been established. 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 practice. Safety data of sildenafil citrate in adults were obtained from the 12-week, placebo-controlled clinical study (Study 1) and an open-label extension study in 277 sildenafil citrate-treated patients with PAH, WHO Group I Diagnostic Classification.

Side Effect	Severity	Common Symptoms	Frequency
Headache	Mild to Moderate	Throbbing pain, sensation of pressure	Very common
Flushing	Mild	Skin redness, warmth	Common
Dyspepsia (Indigestion)	Mild	Burning sensation in stomach	Common
Visual disturbances	Mild to moderate	Blue tint, blurred vision	Less common
Priapism	Severe	Prolonged and painful erection	Rare

The overall frequency of discontinuation in sildenafil citrate-treated patients 20 mg TID was 3% and was the same for the placebo group. In Study 1, the adverse reactions that were reported by at least 3% of sildenafil citrate-treated patients (20 mg TID) and were more frequent in sildenafil citrate-treated patients than in placebo-treated patients are shown in Table 1. Adverse reactions were generally transient and mild to moderate in nature. At doses higher than the recommended 20 mg TID, there was a greater sildenafil for women incidence of some adverse reactions including flushing, diarrhea, myalgia and visual disturbances. Visual disturbances were identified as mild and transient, and were predominately color-tinge to vision, but also increased sensitivity to light or blurred vision. The incidence of retinal hemorrhage with sildenafil citrate 20 mg TID was 1.4% versus 0% placebo and for all sildenafil citrate doses studied was 1.9% versus 0% placebo. The incidence of eye hemorrhage at both 20 mg TID and at all doses studied was 1.4% for sildenafil citrate versus 1.4% for placebo. The patients experiencing these reactions had risk factors for hemorrhage including concurrent anticoagulant therapy. In a placebo-controlled fixed dose titration study (Study 2) of sildenafil citrate (starting with recommended dose of 20 mg TID and increased to 40 mg TID and then 80 mg TID) as an adjunct to intravenous epoprostenol in patients with PAH, the adverse reactions that were more frequent in the sildenafil citrate + epoprostenol group than in the epoprostenol group (greater than 6% difference) are shown in Table 2 . The following adverse reactions have been identified during post approval use of * Sildenafil (marketed for both PAH and erectile dysfunction). Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. In postmarketing experience with sildenafil at doses indicated for erectile dysfunction, serious cardiovascular, cerebrovascular, and vascular events, including myocardial infarction, sudden cardiac death, ventricular arrhythmia, cerebrovascular hemorrhage, transient ischemic attack, hypertension, pulmonary hemorrhage, and subarachnoid and intracerebral hemorrhages have been reported in temporal association with the use of the drug.

Potential Side Effects and Safety

Based on published literature, the annual incidence of NAION is 2.5-11.8 cases per 100,000 males aged ≥ 50 per year in the general population. An observational study evaluated whether recent, episodic use of PDE5 inhibitors (as a class), typical of erectile dysfunction treatment, was associated with acute onset of NAION. The results suggest an approximately 2-fold increase in the risk of NAION within 5 half-lives of PDE5 inhibitor use. It is not possible to determine whether these events are related directly to the use of PDE-5 inhibitors, to the patient’s underlying vascular risk factors or anatomical defects, to a combination of these factors, or to other factors. Advise patients to seek immediate medical attention in the event of a sudden loss of vision in one or both eyes while taking PDE-5 inhibitors, including sildenafil citrate.

What is sildenafil, and what is it used for?

Physicians should also discuss the increased risk of NAION with patients who have already experienced NAION in one eye, including whether such individuals could be adversely affected by use of vasodilators, such as PDE-5 inhibitors. There are no controlled clinical data on the safety or efficacy of sildenafil citrate in patients with retinitis pigmentosa, a minority whom have genetic disorders of retinal phosphodiesterases. Prescribe sildenafil citrate with caution in these patients. Cases of sudden decrease or loss of hearing, which may be accompanied by tinnitus and dizziness, have been reported in temporal association with the use of PDE-5 inhibitors, including sildenafil citrate. In some of the cases, medical conditions and other factors were reported that may have played a role.

FDA-Labeled Indications and Dosage (Adult)

In many cases, medical follow-up information was limited. It is not possible to determine whether these reported events are related directly to the use of sildenafil citrate, to the patient’s underlying risk factors for hearing loss, a combination of these factors, or to other factors. Advise patients to seek prompt medical attention in the event of sudden decrease or loss of hearing while taking PDE-5 inhibitors, including sildenafil citrate. Sildenafil is also marketed as Sildenafil citrate®. The safety and efficacy of combinations of sildenafil citrate with Sildenafil citrate or other PDE-5 inhibitors have not been studied. Most, but not all, of these patients had preexisting cardiovascular risk factors. Many of these events were reported to occur during or shortly after sexual activity, and a few were reported to occur shortly after the use of sildenafil without sexual activity.

Condition	Description	Recommended Dosage	Notes
Erectile Dysfunction (ED)	Difficulty achieving or maintaining an erection	50 mg before activity	Can be adjusted based on response
Pulmonary Arterial Hypertension	High blood pressure in lungs	20 mg three times daily	Prescribed under medical supervision
Off-label uses	Other potential uses	Varies	Use under healthcare provider guidance

Others were reported to have occurred hours to days after use concurrent with sexual activity.

6. Response and effectiveness

Inform patients taking sildenafil citrate not to take Sildenafil citrate or other PDE5 inhibitors. In the event of an erection that persists longer than 4 hours, the patient should seek immediate medical assistance. If priapism (painful erection greater than 6 hours in duration) is not treated immediately, penile tissue damage and permanent loss of potency could result. In a small, prematurely terminated study of patients with pulmonary hypertension (PH) secondary to sickle cell disease, vaso-occlusive crises requiring hospitalization were more commonly reported by patients who received sildenafil citrate than by those randomized to placebo. The effectiveness and safety of sildenafil citrate in the treatment of PAH secondary to sickle cell anemia has not been established.

Most Recent Events

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 practice. Safety data of sildenafil citrate in adults were obtained from the 12-week, placebo-controlled clinical study (Study 1) and an open-label extension study in 277 sildenafil citrate-treated patients with PAH, WHO Group I Diagnostic Classification. The overall frequency of discontinuation in sildenafil citrate-treated patients 20 mg TID was 3% and was the same for the placebo group. In Study 1, the adverse reactions that were reported by at least 3% of sildenafil citrate-treated patients (20 mg TID) and were more frequent in sildenafil citrate-treated patients than in placebo-treated patients are shown in Table 1. Adverse reactions were generally transient and mild to moderate in nature.

Pediatric Precautions

At doses higher than the recommended 20 mg TID, there was a greater sildenafil for women incidence of some adverse reactions including flushing, diarrhea, myalgia and visual disturbances. Visual disturbances were identified as mild and transient, and were predominately color-tinge to vision, but also increased sensitivity to light or blurred vision. The incidence of retinal hemorrhage with sildenafil citrate 20 mg TID was 1.4% versus 0% placebo and for all sildenafil citrate doses studied was 1.9% versus 0% placebo. The incidence of eye hemorrhage at both 20 mg TID and at all doses studied was 1.4% for sildenafil citrate versus 1.4% for placebo. The patients experiencing these reactions had risk factors for hemorrhage including concurrent anticoagulant therapy. It is not possible to determine whether these events are related directly to sildenafil, to sexual activity, to the patient’s underlying cardiovascular disease, or to a combination of these or other factors. Concomitant use of sildenafil citrate with nitrates in any form is contraindicated. Concomitant use of sildenafil citrate with ritonavir and other potent CYP3A inhibitors is not recommended. In drug-drug interaction studies, sildenafil (25 mg, 50 mg, or 100 mg) and the alpha-blocker doxazosin (4 mg or 8 mg) were administered simultaneously to patients with benign prostatic hyperplasia (BPH) stabilized on doxazosin therapy. In these study populations, mean additional reductions of supine systolic and diastolic blood pressure of 7/7 mmHg, 9/5 mmHg, and 8/4 mmHg, respectively, were observed. Mean additional reductions of standing blood pressure of 6/6 mmHg, 11/4 mmHg, and 4/5 mmHg, respectively, were also observed. There were infrequent reports of patients who experienced symptomatic postural hypotension.

• Contraindications include use with nitrates and recent heart attack.
• Patients with contraindications should avoid sildenafil entirely.
• Visual disturbances including blue-tinted vision may occur.
• Use caution in patients with liver or kidney impairment.
• Sildenafil can interact with certain antibiotics and antifungals.
• Always inform your doctor about other medications you're taking.
• It does not protect against sexually transmitted infections.

These reports included dizziness and light-headedness, but not syncope. When sildenafil 100 mg oral was co-administered with amlodipine, 5 mg or 10 mg oral, to hypertensive patients, the mean additional reduction on supine blood pressure was 8 mmHg systolic and 7 mmHg diastolic. There are no adequate and well-controlled studies of sildenafil in pregnant women. 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/m2 basis, 32- and 68-times, respectively, the recommended human dose (RHD) of 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/m2 basis). Pregnancy Category (AUS): There is no Australian Drug Evaluation Committee (ADEC) guidance on usage of Sildenafil in women who are pregnant. The safety and efficacy of sildenafil citrate during labor and delivery has not been studied. It is not known if sildenafil or its metabolites are excreted in human breast milk. Because many drugs are excreted in human milk, caution should be exercised when sildenafil citrate is administered to a nursing woman. 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 citrate, 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. The primary objective of the study was to assess the effect of sildenafil citrate on exercise capacity as measured by cardiopulmonary exercise testing in pediatric patients developmentally able to perform the test (n = 115).

• Sildenafil’s development marked a breakthrough in ED treatment.
• It has revolutionized sexual health for many men globally.
• The drug’s mechanism enhances nitric oxide effects.
• Many patients report improved confidence with sildenafil use.
• Research continues on new formulations and delivery methods.
• Public health campaigns promote safe and effective usage.
• Awareness of contraindications reduces health risks.

Administration of sildenafil citrate 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 citrate remained on his/her dose of sildenafil citrate or, if originally randomized to placebo, was randomized to low-, medium-, or high-dose sildenafil citrate. After all patients completed 16 weeks of follow-up in the controlled study, the blind was broken and doses were adjusted as clinically indicated.