Viagra: How a Little Blue Pill Changed the World

In the nonpregnant rat the AUC at this dose was about 20 times human AUC.8.4 Pediatric UseVIAGRA 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)].

5.5 Hypotension when Co-administered with Alpha-blockers or Anti-hypertensives

Related medical questions

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 [see Clinical Pharmacology (12.3)].Of the total number of subjects in clinical studies of Viagra, 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.

7.2 Alpha-blockers

A starting dose of 25 mg should be considered in patients with severe renal impairment [see Dosage and Administration (2.5) and Clinical Pharmacology (12.3)].8.7 Hepatic ImpairmentIn volunteers with hepatic impairment (Child-Pugh Class A and B), sildenafil clearance was reduced, resulting in higher plasma exposure of sildenafil (47% for Cmax and 85% for AUC). VIAGRA is not indicated for use in women. There are no adequate and well-controlled studies of sildenafil in pregnant women.

Based on animal data, VIAGRA is not predicted to increase the risk of adverse developmental outcomes in humans. No evidence of teratogenicity, embryotoxicity or fetotoxicity was observed in rats and rabbits which received up to 200 mg/kg/day during organogenesis.

In the nonpregnant rat the AUC at this dose was about 20 times human AUC.

Chemical synthesis

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. 11 DESCRIPTION VIAGRA (sildenafil citrate), an oral therapy for erectile dysfunction, is the citrate salt of sildenafil, a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5).Sildenafil citrate is designated chemically as 1-[[3-(6,7-dihydro-1-methyl-7-oxo-3-propyl-1H-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.VIAGRA is formulated as blue, film-coated rounded-diamond-shaped tablets equivalent to 25 mg, 50 mg and 100 mg of sildenafil for oral administration. 12 CLINICAL PHARMACOLOGY 12.1 Mechanism of ActionThe 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 at recommended doses has no effect in the absence of sexual stimulation.Binding CharacteristicsStudies in vitro viagra click and collect have shown that sildenafil is selective for PDE5.

How to relieve Viagra side effects

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 VIAGRA 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 VIAGRA administration compared with placebo. 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 VIAGRA 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). Larger effects were recorded among patients receiving concomitant nitrates [see Contraindications (4.1)].Effects of VIAGRA 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). 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 VIAGRA 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 VIAGRA with doxazosin, an alpha-adrenergic blocking agent.Study 1: VIAGRA with DoxazosinIn the first study, a single oral dose of VIAGRA 100 mg or matching placebo was administered in a 2-period crossover design to 4 generally healthy males with benign prostatic hyperplasia (BPH). 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.

Route of administration

The mean subject age was 66.5 years.For the 17 subjects who received VIAGRA 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 VIAGRA or matching placebo are shown in Figure 2.Figure 2: Mean Standing Systolic Blood Pressure Change from BaselineBlood 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 VIAGRA or matching placebo. No severe adverse events potentially related to blood pressure effects were reported in this group.Of the four subjects who received VIAGRA 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 VIAGRA 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). 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: VIAGRA with DoxazosinIn the second study, a single oral dose of VIAGRA 50 mg or matching placebo was administered in a 2-period crossover design to 20 generally healthy males with BPH. The mean subject age in this study was 63.9 years.Twenty subjects received VIAGRA 50 mg, but only 19 subjects received matching placebo. This patient had been taking minoxidil, a potent vasodilator, during the study.For the 19 subjects who received both VIAGRA 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 VIAGRA or matching placebo are shown in Figure 3.Figure 3: Mean Standing Systolic Blood Pressure Change from BaselineBlood pressure was measured after administration of VIAGRA at the same times as those specified for the first doxazosin study.

How is sildenafil supplied (dosage forms)?

There were no severe adverse events potentially related to blood pressure and no episodes of syncope reported in this study.Study 3: VIAGRA with DoxazosinIn the third study, a single oral dose of VIAGRA 100 mg or matching placebo was administered in a 3-period crossover design to 20 generally healthy males with BPH. 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 VIAGRA 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 VIAGRA 50 mg).For the 20 subjects who received VIAGRA 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 VIAGRA or matching placebo are shown in Figure 4.Figure 4: Mean Standing Systolic Blood Pressure Change from BaselineBlood pressure was measured after administration of VIAGRA at the same times as those specified for the previous doxazosin studies. 11 DESCRIPTION VIAGRA (sildenafil citrate), an oral therapy for erectile dysfunction, is the citrate salt of sildenafil, a selective inhibitor of cyclic guanosine monophosphate (cGMP)-specific phosphodiesterase type 5 (PDE5).Sildenafil citrate is designated chemically as 1-[[3-(6,7-dihydro-1-methyl-7-oxo-3-propyl-1H-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.VIAGRA is formulated as blue, film-coated rounded-diamond-shaped tablets equivalent to 25 mg, 50 mg and 100 mg of sildenafil for oral administration. 12 CLINICAL PHARMACOLOGY 12.1 Mechanism of ActionThe 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.

• Viagra mimics the effects of natural nitric oxide in the body.
• It is important to take Viagra exactly as prescribed.
• The medication can cause headaches due to vasodilation.
• Viagra’s onset and duration vary among users.
• Exercise caution if you experience chest pain or severe dizziness.
• Always inform your doctor about any other medications taken.

Sildenafil at recommended doses has no effect in the absence of sexual stimulation.Binding CharacteristicsStudies in vitro viagra click and collect have shown that sildenafil is selective for PDE5. 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 VIAGRA 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 VIAGRA administration compared with placebo. 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 VIAGRA 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). Larger effects were recorded among patients receiving concomitant nitrates [see Contraindications (4.1)].Effects of VIAGRA 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).

• Viagra has helped millions of men regain sexual confidence.
• The medication can be part of a broader approach to sexual health.
• Proper dosing is vital to avoid adverse effects.
• Always read the patient information leaflet thoroughly.
• Be aware of potential interactions with other prescriptions.
• Open communication with your doctor leads to better outcomes.

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 VIAGRA 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 VIAGRA with doxazosin, an alpha-adrenergic blocking agent.Study 1: VIAGRA with DoxazosinIn the first study, a single oral dose of VIAGRA 100 mg or matching placebo was administered in a 2-period crossover design to 4 generally healthy males with benign prostatic hyperplasia (BPH). The mean subject age was 66.5 years.For the 17 subjects who received VIAGRA 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 VIAGRA or matching placebo are shown in Figure 2.Figure 2: Mean Standing Systolic Blood Pressure Change from BaselineBlood 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 VIAGRA or matching placebo. No severe adverse events potentially related to blood pressure effects were reported in this group.Of the four subjects who received VIAGRA 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 VIAGRA 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). 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: VIAGRA with DoxazosinIn the second study, a single oral dose of VIAGRA 50 mg or matching placebo was administered in a 2-period crossover design to 20 generally healthy males with BPH. The mean subject age in this study was 63.9 years.Twenty subjects received VIAGRA 50 mg, but only 19 subjects received matching placebo. This patient had been taking minoxidil, a potent vasodilator, during the study.For the 19 subjects who received both VIAGRA 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 VIAGRA or matching placebo are shown in Figure 3.Figure 3: Mean Standing Systolic Blood Pressure Change from BaselineBlood pressure was measured after administration of VIAGRA at the same times as those specified for the first doxazosin study. There were no severe adverse events potentially related to blood pressure and no episodes of syncope reported in this study.Study 3: VIAGRA with DoxazosinIn the third study, a single oral dose of VIAGRA 100 mg or matching placebo was administered in a 3-period crossover design to 20 generally healthy males with BPH. 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 VIAGRA 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 VIAGRA 50 mg).For the 20 subjects who received VIAGRA 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 VIAGRA or matching placebo are shown in Figure 4.Figure 4: Mean Standing Systolic Blood Pressure Change from BaselineBlood pressure was measured after administration of VIAGRA at the same times as those specified for the previous doxazosin studies.

12.1 Mechanism of Action

In the nonpregnant rat the AUC at this dose was about 20 times human AUC.8.4 Pediatric UseVIAGRA 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 [see Clinical Pharmacology (12.3)].Of the total number of subjects in clinical studies of Viagra, 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. A starting dose of 25 mg should be considered in patients with severe renal impairment [see Dosage and Administration (2.5) and Clinical Pharmacology (12.3)].8.7 Hepatic ImpairmentIn volunteers with hepatic impairment (Child-Pugh Class A and B), sildenafil clearance was reduced, resulting in higher plasma exposure of sildenafil (47% for Cmax and 85% for AUC).

Pulmonary hypertension

VIAGRA is not indicated for use in women. There are no adequate and well-controlled studies of sildenafil in pregnant women. Based on animal data, VIAGRA is not predicted to increase the risk of adverse developmental outcomes in humans. No evidence of teratogenicity, embryotoxicity or fetotoxicity was observed in rats and rabbits which received up to 200 mg/kg/day during organogenesis. In the nonpregnant rat the AUC at this dose was about 20 times human AUC.