DOSAGE FORMS AND STRENGTHS

Sildenafil is approximately 4,000-fold more selective for PDE5 compared to PDE3. PDE3 is involved in control of cardiac contractility.

AN 354

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.12.2 PharmacodynamicsEffects of Sildenafil on Erectile Response: In eight double-blind, placebo-controlled crossover studies of patients with either organic or psychogenic erectile dysfunction, sexual stimulation resulted in improved erections, as assessed by an objective measurement of hardness and duration of erections (RigiScan®), after sildenafil administration compared with placebo.

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Most studies assessed the efficacy of sildenafil approximately 60 minutes post dose.

• Sildenafil white is sometimes called the "blue pill" in popular culture.
• It remains one of the most prescribed medications for ED worldwide.
• Some individuals purchase sildenafil white without a prescription, which can be risky.
• Derived from a scientific discovery initially aimed at heart treatment.
• Viagra was the first brand to market sildenafil for ED.
• The medication can cause side effects like dizziness and upset stomach.
• Elderly patients should be cautious due to increased risk of side effects.
• Regular medical check-ups are recommended for long-term sildenafil users.
• Lifestyle changes, such as exercise and diet, can enhance treatment results.
• The medication is typically taken on an empty stomach for quicker effect.
• Research continues into new formulations and delivery methods for sildenafil

The erectile response, as assessed by RigiScan®, generally increased with increasing sildenafil dose and plasma concentration. The time course of effect was examined in one study, showing an effect for up to 4 hours but the response was diminished compared to 2 hours.Effects of Sildenafil on Blood Pressure: Single oral doses of sildenafil (100 mg) administered to healthy volunteers produced decreases in sitting blood pressure (mean maximum decrease in systolic/diastolic blood pressure of 8.3/5.3 mmHg). The decrease in sitting blood pressure was most notable approximately 1 to 2 hours after dosing, and was not different than placebo at 8 hours.

Sildenafil Overdose

No severe adverse events potentially related to blood pressure effects were reported in this group.Of the four subjects who received sildenafil 100 mg in the first part of this study, a severe adverse event related to blood pressure effect was reported in one patient (postural hypotension that began 35 minutes after dosing with sildenafil with symptoms lasting for 8 hours), and mild adverse events potentially related to blood pressure effects were reported in two others (dizziness, headache and fatigue at 1 hour after dosing; and dizziness, lightheadedness and nausea at 4 hours after dosing). There were no reports of syncope among these patients. For these four subjects, the placebo-subtracted mean maximum decreases from baseline in supine and standing systolic blood pressures were 14.8 mmHg and 21.5 mmHg, respectively. Two of these subjects had a standing SBP < 85 mmHg. Both of these subjects were protocol violators, one due to a low baseline standing SBP, and the other due to baseline orthostatic hypotension.Study 2: Sildenafil with DoxazosinIn the second study, a single oral dose sildenafil gel of sildenafil 50 mg or matching placebo was administered in a 2-period crossover design to 20 generally healthy males with BPH.

Pulmonary hypertension

Following at least 14 consecutive days of doxazosin, sildenafil 50 mg or matching placebo was administered simultaneously with doxazosin 4 mg (17 subjects) or with doxazosin 8 mg (3 subjects). The mean subject age in this study was 63.9 years.Twenty subjects received sildenafil 50 mg, but only 19 subjects received matching placebo. One patient discontinued the study prematurely due to an adverse event of hypotension following dosing with sildenafil 50 mg. This patient had been taking minoxidil, a potent vasodilator, during the study.For the 19 subjects who received both sildenafil and matching placebo, the placebo-subtracted mean maximum decreases from baseline (95% CI) in systolic blood pressure were as follows:The mean profiles of the change from baseline in standing systolic blood pressure in subjects treated with doxazosin in combination with 50 mg sildenafil or matching placebo are shown in Figure 3.Blood pressure was measured after administration of sildenafil at the same times as those specified for the first doxazosin study. There were two subjects who had a standing SBP of < 85 mmHg. Similar effects on blood pressure were noted with 25 mg, 50 mg and 100 mg of sildenafil, therefore the effects are not related to dose or plasma levels within this dosage range.

• Sildenafil white was first approved by the FDA in 1998.
• It is marketed under various brand and generic names worldwide.
• The drug belongs to a class called phosphodiesterase inhibitors.
• It is effective for many men with both physical and psychological ED.
• Sildenafil white may also help treat pulmonary arterial hypertension.
• Some users report experiencing visual disturbances after taking it.
• The medication’s effects last approximately 4 to 6 hours.
• It is advisable to avoid alcohol when taking sildenafil white.
• Consumers should check for potential drug allergies before use.
• The pill's color and shape can vary depending on the manufacturer.
• Always consult a healthcare provider for appropriate use and dosing.

Larger effects were recorded among patients receiving concomitant nitrates [see Contraindications (4.1)].Effects of Sildenafil on Blood Pressure When Nitroglycerin is Subsequently Administered:Based on the pharmacokinetic profile of a single 100 mg oral dose given to healthy normal volunteers, the plasma levels of sildenafil at 24 hours post dose are approximately 2 ng/mL (compared to peak plasma levels of approximately 440 ng/mL). In the following patients: age >65 years, hepatic impairment (e.g., cirrhosis), severe renal impairment (e.g., creatinine clearance <30 mL/min), and concomitant use of erythromycin or strong CYP3A4 inhibitors, plasma levels of sildenafil at 24 hours post dose have been found to be 3 to 8 times higher than those seen in healthy volunteers. 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 co-administered at this time point [see Contraindications (4.1)].Effects of Sildenafil on Blood Pressure When Co-administered with Alpha-Blockers:Three double-blind, placebo-controlled, randomized, two-way crossover studies were conducted to assess the interaction of sildenafil with doxazosin, an alpha-adrenergic blocking agent.Study 1: Sildenafil with DoxazosinIn the first study, a single oral dose of sildenafil 100 mg or matching placebo was administered in a 2-period crossover design to 4 generally healthy males with benign prostatic hyperplasia (BPH). Following at least 14 consecutive daily doses of doxazosin, sildenafil 100 mg or matching placebo was administered simultaneously with doxazosin. Following a review of the data from these first 4 subjects (details provided below), the sildenafil dose was reduced to 25 mg. Thereafter, 17 subjects were treated with sildenafil 25 mg or matching placebo in combination with doxazosin 4 mg (15 subjects) or doxazosin 8 mg (2 subjects). The mean subject age was 66.5 years.For the 17 subjects who received sildenafil 25 mg and matching placebo, the placebo-subtracted mean maximum decreases from baseline (95% CI) in systolic blood pressure were as follows:The mean profiles of the change from baseline in standing systolic blood pressure in subjects treated with doxazosin in combination with 25 mg sildenafil or matching placebo are shown in Figure 2.Blood pressure was measured immediately pre-dose and at 15, 30, 45 minutes, and 1, 1.5, 2, 2.5, 3, 4, 6 and 8 hours after sildenafil or matching placebo. Outliers were defined as subjects with a standing systolic blood pressure of <85 mmHg or a decrease from baseline in standing systolic blood pressure of >30 mmHg at one or more timepoints. There were no subjects treated with sildenafil 25 mg who had a standing SBP < 85 mmHg. There were three subjects with a decrease from baseline in standing systolic BP >30 mmHg following sildenafil 25 mg, one subject with a decrease from baseline in standing systolic BP > 30 mmHg following placebo and two subjects with a decrease from baseline in standing systolic BP > 30 mmHg following both sildenafil and placebo. No severe adverse events potentially related to blood pressure effects were reported in this group.Of the four subjects who received sildenafil 100 mg in the first part of this study, a severe adverse event related to blood pressure effect was reported in one patient (postural hypotension that began 35 minutes after dosing with sildenafil with symptoms lasting for 8 hours), and mild adverse events potentially related to blood pressure effects were reported in two others (dizziness, headache and fatigue at 1 hour after dosing; and dizziness, lightheadedness and nausea at 4 hours after dosing). There were no reports of syncope among these patients. For these four subjects, the placebo-subtracted mean maximum decreases from baseline in supine and standing systolic blood pressures were 14.8 mmHg and 21.5 mmHg, respectively.

Sildenafil Cautionary Labels

In these two subjects, hypotension was reported as a moderately severe adverse event, beginning at approximately 1 hour after administration of sildenafil 50 mg and resolving after approximately 7.5 hours. There was one subject with a decrease from baseline in standing systolic BP >30 mmHg following sildenafil 50 mg and one subject with a decrease from baseline in standing systolic BP > 30 mmHg following both sildenafil 50 mg and placebo. There were no severe adverse events potentially related to blood pressure and no episodes of syncope reported in this study.Study 3: Sildenafil with DoxazosinIn the third study, a single oral dose of sildenafil 100 mg or matching placebo was administered in a 3-period crossover design to 20 generally healthy males with BPH. In dose period 1, subjects were administered open-label doxazosin and a single dose of sildenafil 50 mg simultaneously, after at least 14 consecutive days of doxazosin. If a subject did not successfully complete this first dosing period, he was discontinued from the study.

Viagra Super Active

Subjects who had successfully completed the previous doxazosin interaction study (using sildenafil 50 mg), including no significant hemodynamic adverse events, were allowed to skip dose period 1. Treatment with doxazosin continued for at least 7 days after dose period 1. Thereafter, sildenafil 100 mg or matching placebo was administered simultaneously with doxazosin 4 mg (14 subjects) or doxazosin 8 mg (6 subjects) in standard crossover fashion. The mean subject age in this study was 66.4 years.Twenty-five subjects were screened. Two were discontinued after study period 1: one failed to meet pre-dose screening qualifications and the other experienced symptomatic hypotension as a moderately severe adverse event 30 minutes after dosing with open-label sildenafil 50 mg. Two of these subjects had a standing SBP < 85 mmHg. Both of these subjects were protocol violators, one due to a low baseline standing SBP, and the other due to baseline orthostatic hypotension.Study 2: Sildenafil with DoxazosinIn the second study, a single oral dose sildenafil gel of sildenafil 50 mg or matching placebo was administered in a 2-period crossover design to 20 generally healthy males with BPH. Following at least 14 consecutive days of doxazosin, sildenafil 50 mg or matching placebo was administered simultaneously with doxazosin 4 mg (17 subjects) or with doxazosin 8 mg (3 subjects). The mean subject age in this study was 63.9 years.Twenty subjects received sildenafil 50 mg, but only 19 subjects received matching placebo. One patient discontinued the study prematurely due to an adverse event of hypotension following dosing with sildenafil 50 mg. This patient had been taking minoxidil, a potent vasodilator, during the study.For the 19 subjects who received both sildenafil and matching placebo, the placebo-subtracted mean maximum decreases from baseline (95% CI) in systolic blood pressure were as follows:The mean profiles of the change from baseline in standing systolic blood pressure in subjects treated with doxazosin in combination with 50 mg sildenafil or matching placebo are shown in Figure 3.Blood pressure was measured after administration of sildenafil at the same times as those specified for the first doxazosin study. There were two subjects who had a standing SBP of < 85 mmHg.

• Sildenafil white is a common name for the generic version of Viagra.
• It is used to treat erectile dysfunction in men.
• Sildenafil white is known for its rapid onset of action.
• The medication works by enhancing blood flow to the penis.
• It is typically taken about 30 to 60 minutes before sexual activity.
• Sildenafil white is available in various doses, usually 25mg, 50mg, and 100mg.
• The drug should not be used with nitrate medications to avoid dangerous interactions.
• Common side effects include headache, flushing, and nasal congestion.
• It is important to follow dosage instructions provided by a healthcare provider.
• Sildenafil white can cause low blood pressure in some users.
• Store sildenafil white in a cool, dry place, away from direct sunlight.

In these two subjects, hypotension was reported as a moderately severe adverse event, beginning at approximately 1 hour after administration of sildenafil 50 mg and resolving after approximately 7.5 hours.

2.3 Dosage Adjustments in Specific Situations

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.12.2 PharmacodynamicsEffects of Sildenafil on Erectile Response: In eight double-blind, placebo-controlled crossover studies of patients with either organic or psychogenic erectile dysfunction, sexual stimulation resulted in improved erections, as assessed by an objective measurement of hardness and duration of erections (RigiScan®), after sildenafil administration compared with placebo.

Are you currently using Sildenafil (Viagra, Revatio)?

Most studies assessed the efficacy of sildenafil approximately 60 minutes post dose. The erectile response, as assessed by RigiScan®, generally increased with increasing sildenafil dose and plasma concentration. The time course of effect was examined in one study, showing an effect for up to 4 hours but the response was diminished compared to 2 hours.Effects of Sildenafil on Blood Pressure: Single oral doses of sildenafil (100 mg) administered to healthy volunteers produced decreases in sitting blood pressure (mean maximum decrease in systolic/diastolic blood pressure of 8.3/5.3 mmHg). The decrease in sitting blood pressure was most notable approximately 1 to 2 hours after dosing, and was not different than placebo at 8 hours. Similar effects on blood pressure were noted with 25 mg, 50 mg and 100 mg of sildenafil, therefore the effects are not related to dose or plasma levels within this dosage range. There was one subject with a decrease from baseline in standing systolic BP >30 mmHg following sildenafil 50 mg and one subject with a decrease from baseline in standing systolic BP > 30 mmHg following both sildenafil 50 mg and placebo.

Drug Type	Effect on Sildenafil White	Notes
Nitrates	Potentiate hypotensive effects	Contraindicated
CYP3A4 Inhibitors	Increase sildenafil levels, risk of side effects	Use lower dose if necessary
Alpha-blockers	Risk of hypotension	Monitor blood pressure
P450 Enzyme Inducers	Decrease effectiveness	Monitor and adjust dosage

There were no severe adverse events potentially related to blood pressure and no episodes of syncope reported in this study.Study 3: Sildenafil with DoxazosinIn the third study, a single oral dose of sildenafil 100 mg or matching placebo was administered in a 3-period crossover design to 20 generally healthy males with BPH.

• The term 'sildenafil white' often refers to unbranded, generic pills.
• It may be available online through various pharmacies and vendors.
• Users should verify the legitimacy of sildenafil sources to avoid fake products.
• This medication is not suitable for individuals with certain heart conditions.
• Sildenafil white is sometimes used recreationally for its euphoric effects.
• It may interact with certain antibiotics and antifungals, altering effectiveness.
• Patients should inform their doctor of all medications before use.
• The medication is not an aphrodisiac; it only facilitates erectile response.
• Overuse or misuse of sildenafil white can lead to serious health risks.
• The recommended maximum frequency is once per day unless advised otherwise.
• Consultation with a healthcare professional is essential prior to use.

In dose period 1, subjects were administered open-label doxazosin and a single dose of sildenafil 50 mg simultaneously, after at least 14 consecutive days of doxazosin.

Country/Region	Regulatory Body	Status of Sildenafil White	Notes
United States	FDA	Approved for ED and pulmonary hypertension	Prescription-only
European Union	EMA	Approved, similar indications	Prescription required
Canada	Health Canada	Approved with similar uses	Prescription needed
Australia	TGA	Approved for ED and pulmonary use	Prescription-only
India	CDSCO	Approved, widely available	Over-the-counter in some states

If a subject did not successfully complete this first dosing period, he was discontinued from the study. Subjects who had successfully completed the previous doxazosin interaction study (using sildenafil 50 mg), including no significant hemodynamic adverse events, were allowed to skip dose period 1.

5.2 Worsening Pulmonary Vascular Occlusive Disease

Larger effects were recorded among patients receiving concomitant nitrates [see Contraindications (4.1)].Effects of Sildenafil on Blood Pressure When Nitroglycerin is Subsequently Administered:Based on the pharmacokinetic profile of a single 100 mg oral dose given to healthy normal volunteers, the plasma levels of sildenafil at 24 hours post dose are approximately 2 ng/mL (compared to peak plasma levels of approximately 440 ng/mL). In the following patients: age >65 years, hepatic impairment (e.g., cirrhosis), severe renal impairment (e.g., creatinine clearance <30 mL/min), and concomitant use of erythromycin or strong CYP3A4 inhibitors, plasma levels of sildenafil at 24 hours post dose have been found to be 3 to 8 times higher than those seen in healthy volunteers. 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 co-administered at this time point [see Contraindications (4.1)].Effects of Sildenafil on Blood Pressure When Co-administered with Alpha-Blockers:Three double-blind, placebo-controlled, randomized, two-way crossover studies were conducted to assess the interaction of sildenafil with doxazosin, an alpha-adrenergic blocking agent.Study 1: Sildenafil with DoxazosinIn the first study, a single oral dose of sildenafil 100 mg or matching placebo was administered in a 2-period crossover design to 4 generally healthy males with benign prostatic hyperplasia (BPH). Following at least 14 consecutive daily doses of doxazosin, sildenafil 100 mg or matching placebo was administered simultaneously with doxazosin. Following a review of the data from these first 4 subjects (details provided below), the sildenafil dose was reduced to 25 mg.

Sildenafil preparation and administration

Thereafter, 17 subjects were treated with sildenafil 25 mg or matching placebo in combination with doxazosin 4 mg (15 subjects) or doxazosin 8 mg (2 subjects). The mean subject age was 66.5 years.For the 17 subjects who received sildenafil 25 mg and matching placebo, the placebo-subtracted mean maximum decreases from baseline (95% CI) in systolic blood pressure were as follows:The mean profiles of the change from baseline in standing systolic blood pressure in subjects treated with doxazosin in combination with 25 mg sildenafil or matching placebo are shown in Figure 2.Blood pressure was measured immediately pre-dose and at 15, 30, 45 minutes, and 1, 1.5, 2, 2.5, 3, 4, 6 and 8 hours after sildenafil or matching placebo. Outliers were defined as subjects with a standing systolic blood pressure of <85 mmHg or a decrease from baseline in standing systolic blood pressure of >30 mmHg at one or more timepoints. There were no subjects treated with sildenafil 25 mg who had a standing SBP < 85 mmHg. There were three subjects with a decrease from baseline in standing systolic BP >30 mmHg following sildenafil 25 mg, one subject with a decrease from baseline in standing systolic BP > 30 mmHg following placebo and two subjects with a decrease from baseline in standing systolic BP > 30 mmHg following both sildenafil and placebo. Treatment with doxazosin continued for at least 7 days after dose period 1.

AN 351

Thereafter, sildenafil 100 mg or matching placebo was administered simultaneously with doxazosin 4 mg (14 subjects) or doxazosin 8 mg (6 subjects) in standard crossover fashion. The mean subject age in this study was 66.4 years.Twenty-five subjects were screened.

Step	Description	Equipment Needed
Raw Material Preparation	Sourcing and testing chemical reagents	Reaction vessels, pH meters
Chemical Synthesis	Formation of sildenafil via chemical reactions	Reactors, stirring devices
Purification	Removing impurities through filtration or chromatography	Filtration units, chromatography columns
Tablet Compression	Forming pills from powder	Tablet press, molds
Packaging	Wrapping, labeling, and boxing	Packaging machines, labels

Two were discontinued after study period 1: one failed to meet pre-dose screening qualifications and the other experienced symptomatic hypotension as a moderately severe adverse event 30 minutes after dosing with open-label sildenafil 50 mg. Of the twenty subjects who were ultimately assigned to treatment, a total of 13 subjects successfully completed dose period 1, and seven had successfully completed the previous doxazosin study (using sildenafil 50 mg).For the 20 subjects who received sildenafil 100 mg and matching placebo, the placebo-subtracted mean maximum decreases from baseline (95% CI) in systolic blood pressure were as follows:The mean profiles of the change from baseline in standing systolic blood pressure in subjects treated with doxazosin in combination with 100 mg sildenafil or matching placebo are shown in Figure 4.Blood pressure was measured after administration of sildenafil at the same times as those specified for the previous doxazosin studies.

5.1 Cardiovascular

Of the twenty subjects who were ultimately assigned to treatment, a total of 13 subjects successfully completed dose period 1, and seven had successfully completed the previous doxazosin study (using sildenafil 50 mg).For the 20 subjects who received sildenafil 100 mg and matching placebo, the placebo-subtracted mean maximum decreases from baseline (95% CI) in systolic blood pressure were as follows:The mean profiles of the change from baseline in standing systolic blood pressure in subjects treated with doxazosin in combination with 100 mg sildenafil or matching placebo are shown in Figure 4.Blood pressure was measured after administration of sildenafil at the same times as those specified for the previous doxazosin studies.

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