Where Did the Viagra Spam Come From? This Time, From Pfizer

Adverse effects
Articles in this issue
Benefits Of Pfizer Viagra 50mg Tablet 2s
Cơ chế
Chống chỉ định
What is Viagra?
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Condition	Warning Level	Reason
Uncontrolled hypertension	High	Risk of severe hypotension
Cardiovascular disease	High	Increased cardiac risk
Use of nitrate medications	High	Dangerous drop in blood pressure
Retinitis pigmentosa	Moderate	Potential retinal complications

Use caution when co-administering alpha-blockers with VIAGRA because of potential additive blood pressure-lowering effects. When VIAGRA is co-administered with an alpha-blocker, patients should be stable on alpha-blocker therapy prior to initiating VIAGRA treatment and VIAGRA should be initiated at the lowest dose [see Dosage and Administration (2.3),Warnings and Precautions (5.5), Clinical Pharmacology (12.2)].

Adverse effects

Safety and effectiveness have not been established in pediatric patients. Healthy 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.

What would happen if I took a larger dose of Viagra than my doctor prescribed — for example, 150 mg or 200 mg?

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)]. No dose adjustment is required for mild (CLcr=50–80 mL/min) and moderate (CLcr=30–49 mL/min) renal impairment. In volunteers with severe renal impairment (Clcr<30 mL/min), sildenafil clearance was reduced, resulting in higher plasma exposure of sildenafil (~2 fold), approximately doubling of Cmax and AUC. 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)]. In 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). When VIAGRA 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)].

Product	Dosage	Quantity + Bonus	Price
Viagra Generic	25mg	10 Pills	25.19€ 23.99€
Viagra Generic	50mg	60 + 4 Pills	83.93€ 79.93€
Viagra Soft Tabs	100mg	90 + 6 Pills	205.31€ 195.53€
Viagra Generic	200mg	120 + 8 Pills	204.80€ 195.05€
Viagra Original	100mg	34 + 2 Pills	163.67€ 155.88€
Viagra Generic	150mg	270 + 10 Pills	326.61€ 311.06€
Viagra Original	100mg	120 + 8 Pills	470.39€ 447.99€
Viagra Generic	25mg	120 + 6 Pills	125.56€ 119.58€
Viagra Generic	200mg	60 + 4 Pills	125.19€ 119.23€
Viagra Generic	50mg	360 + 10 Pills	225.33€ 214.60€
Viagra Generic	150mg	30 + 2 Pills	72.32€ 68.88€
Viagra Generic	25mg	270 + 8 Pills	184.26€ 175.49€
Viagra Generic	100mg	60 + 4 Pills	96.36€ 91.77€
Viagra Oral Jelly	100mg	30 + 5 Sachets	115.76€ 110.25€
Viagra Generic	150mg	120 + 8 Pills	177.58€ 169.12€
Viagra Generic	100mg	270 + 10 Pills	270.47€ 257.59€

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 VIAGRA 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 VIAGRA 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)]. 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)]. VIAGRA is not indicated for use in females. There are no data with the use of VIAGRA in pregnant women to inform any drug-associated risks for adverse developmental outcomes. Animal reproduction studies conducted with sildenafil did not show adverse developmental outcomes when administered during organogenesis in rats and rabbits at oral doses up to 16 and 32 times, respectively, the maximum recommended human dose (MRHD) of 100 mg/day on a mg/m2 basis (see Data). No evidence of teratogenicity, embryotoxicity or fetotoxicity was observed in rats and rabbits which received oral doses up to 200 mg/kg/day during organogenesis. These doses represent, respectively, about 16 and 32 times the MRHD on a mg/m2 basis in a 50 kg subject.

Articles in this issue

Why is the use of Viagra contraindicated with nitrates?

VIAGRA is formulated as blue, film-coated rounded-diamond-shaped tablets equivalent to 25 mg, 50 mg and viagra alternative uk 100 mg of sildenafil for oral administration. 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. 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. In the rat pre- and postnatal development study, the no observed adverse effect dose was 30 mg/kg/day given for 36 days, about 2 times the MRHD on a mg/m2 basis in a 50 kg subject. VIAGRA is not indicated for use in pediatric patients.

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Pfizer's development of Viagra was a key milestone in sexual medicine.
The drug has been credited with increasing awareness of sexual health.
Viagra's impact on male aging and health has been extensively studied.

Benefits Of Pfizer Viagra 50mg Tablet 2s

Urogenital: prolonged erection, priapism [see Warnings and Precautions (5.2) and Patient Counseling Information (17)], and hematuria. Administration of VIAGRA 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, VIAGRA was shown to potentiate the hypotensive effects of nitrates [see Dosage and Administration (2.3), Contraindications (4.1), Clinical Pharmacology (12.2)]. Use caution when co-administering alpha-blockers with VIAGRA because of potential additive blood pressure-lowering effects. When VIAGRA is co-administered with an alpha-blocker, patients should be stable on alpha-blocker therapy prior to initiating VIAGRA treatment and VIAGRA should be initiated at the lowest dose [see Dosage and Administration (2.3),Warnings and Precautions (5.5), Clinical Pharmacology (12.2)].

Drug Interactions Table

When VIAGRA 100 mg was co-administered with amlodipine (5 mg or 10 mg) to hypertensive patients, the mean additional reduction on supine blood pressure was 8 mmHg systolic and 7 mmHg diastolic [see Warnings and Precautions (5.5), Clinical Pharmacology (12.2)]. Co-administration of ritonavir, a strong CYP3A4 inhibitor, greatly increased the systemic exposure of sildenafil (11-fold increase in AUC). It is therefore recommended not to exceed a maximum single dose of 25 mg of VIAGRA 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. In volunteers with severe renal impairment (Clcr<30 mL/min), sildenafil clearance was reduced, resulting in higher plasma exposure of sildenafil (~2 fold), approximately doubling of Cmax and AUC. 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)]. In 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).

Pfizer marketed Viagra as a revolutionary erectile dysfunction drug in the late 1990s.
Viagra has been studied for potential off-label uses, including pulmonary hypertension.
The drug's popular cultural status boosted Pfizer’s pharmaceutical sales.
Viagra's dosage usually ranges from 25 mg to 100 mg, taken as needed.
It is recommended to take Viagra about an hour before sexual activity.
Viagra's patent expiration led to the rise of multiple generic formulations.
The medication is contraindicated in men with certain heart conditions.
Usage guidelines suggest not exceeding one dose per day.
Pfizer conducted extensive clinical trials to ensure Viagra's safety and efficacy.

The pharmacokinetics of sildenafil in patients with severely impaired hepatic function (Child-Pugh Class C) have not been studied. A starting dose of 25 mg should be considered in patients with any degree of hepatic impairment [see Dosage and Administration (2.5) and Clinical Pharmacology (12.3)]. 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. VIAGRA is formulated as blue, film-coated rounded-diamond-shaped tablets equivalent to 25 mg, 50 mg and viagra alternative uk 100 mg of sildenafil for oral administration. The physiologic mechanism of erection of the penis involves release of nitric oxide (NO) in the corpus cavernosum during sexual stimulation.

Cơ chế

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.

Label Warnings

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. Effects 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. Most studies assessed the efficacy of VIAGRA approximately 60 minutes post dose. 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. 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. 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).

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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.

Chống chỉ định

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 VIAGRA 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)]. 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)]. VIAGRA is not indicated for use in females. There are no data with the use of VIAGRA in pregnant women to inform any drug-associated risks for adverse developmental outcomes.

Raynaud's phenomenon

Animal reproduction studies conducted with sildenafil did not show adverse developmental outcomes when administered during organogenesis in rats and rabbits at oral doses up to 16 and 32 times, respectively, the maximum recommended human dose (MRHD) of 100 mg/day on a mg/m2 basis (see Data). No evidence of teratogenicity, embryotoxicity or fetotoxicity was observed in rats and rabbits which received oral doses up to 200 mg/kg/day during organogenesis. These doses represent, respectively, about 16 and 32 times the MRHD on a mg/m2 basis in a 50 kg subject. In the rat pre- and postnatal development study, the no observed adverse effect dose was 30 mg/kg/day given for 36 days, about 2 times the MRHD on a mg/m2 basis in a 50 kg subject. VIAGRA is not indicated for use in pediatric patients. Effects 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. Most studies assessed the efficacy of VIAGRA approximately 60 minutes post dose.

Region	Units Sold (Millions)	Revenue (USD Millions)	Market Share (%)
North America	10	1500	40
Europe	8	1200	32
Asia-Pacific	6	900	18
Latin America	4	600	10

What is Viagra?

Larger effects were recorded among patients receiving concomitant nitrates [see Contraindications (4.1)]. Figure 1: Mean Change from Baseline in Sitting Systolic Blood Pressure, Healthy Volunteers. 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). 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)]. The decrease in sitting blood pressure was most notable approximately 1–2 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 VIAGRA, therefore the effects are not related to dose or plasma levels within this dosage range. Larger effects were recorded among patients receiving concomitant nitrates [see Contraindications (4.1)]. Figure 1: Mean Change from Baseline in Sitting Systolic Blood Pressure, Healthy Volunteers. 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). 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)].

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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 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). The decrease in sitting blood pressure was most notable approximately 1–2 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 VIAGRA, therefore the effects are not related to dose or plasma levels within this dosage range.