Sildenafil vs Tadalafil: What's the difference?

After either oral or intravenous administration, sildenafil is excreted

• Special populations require careful consideration before prescribing.
• In elderly patients (65+), clearance may be reduced; start with a lower dose.
• No dose adjustment is typically needed for patients with mild renal impairment.
• For moderate renal impairment (CrCl 30-80 mL/min), caution is advised.
• In severe renal impairment (CrCl <30 mL/min), a 25mg dose is often recommended.
• For hepatic impairment (Child-Pugh A and B), a 25mg starting dose is advised.
• Sildenafil is not recommended for patients with severe hepatic impairment.
• Safety and efficacy in pediatric patients for ED have not been established.
• Revatio is approved for pediatric PAH patients aged 1 year and older.
• The dose for pediatric PAH is based on body weight and must be carefully calculated.
• Use during pregnancy is only for PAH and requires a careful risk/benefit analysis.

as metabolites predominantly in the feces (approximately 80% of

13. Nonclinical Toxicology

It is eliminated predominantly by hepatic metabolism (mainly CYP3A4) and is converted to an active metabolite with properties similar to the parent, sildenafil. Both sildenafil and the metabolite have terminal half lives of about 4 hours. Mean sildenafil plasma concentrations measured after the administration of a single oral dose of 100 mg to healthy male volunteers is depicted below: Figure 5: Mean Sildenafil Plasma Concentrations in Healthy Male Volunteers. Absorption and Distribution: VIAGRA is rapidly absorbed. When VIAGRA is taken with a high fat meal, the rate of absorption is reduced, with a mean delay in Tmax of 60 minutes and a mean reduction in Cmax of 29%. administered oral dose) and to a lesser extent in

• Sildenafil enhances natural erectile response, requiring sexual stimulation.
• It is not effective as a contraceptive or protection against STDs.
• Alcohol consumption can impair its effectiveness and increase side effects.
• Be cautious if you have low blood pressure or heart issues.
• Combining sildenafil with other ED medications can be dangerous.

the urine (approximately 13% of the administered oral dose).

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Similar values for pharmacokinetic parameters were seen in normal volunteers

Patient Group	Recommended Dose	Frequency of Use	Notes
First-time users	20 mg	Once per day	Take 30-60 min before activity
Experienced users	May increase to 50 mg	As needed	Under medical supervision
Elderly patients	20 mg or lower	As needed	Start with lowest dose
Patients on other medications	Consult doctor	Varies	Adjust dose accordingly

and in the patient population,

• Sildenafil works by relaxing blood vessels to increase blood flow.
• 20mg dosage is suitable for men with mild to moderate ED.
• It is available by prescription or over-the-counter in some regions.
• Avoid alcohol while taking sildenafil to prevent side effects.
• Do not exceed the prescribed dose to reduce health risks.

using a population pharmacokinetic approach.

What Are Warnings and Precautions for Sildenafil?

Based upon measurements of sildenafil in semen of healthy volunteers 90 minutes after dosing, less than 0.001% of the administered dose may appear in the semen of patients. Metabolism and Excretion: Sildenafil is cleared predominantly by the CYP3A4 (major route) and CYP2C9 (minor route) hepatic microsomal isoenzymes. The major circulating metabolite results from N-desmethylation of sildenafil, and is itself further metabolized. This metabolite has a PDE selectivity profile similar to sildenafil and an in vitro potency for PDE5 approximately 50% of the parent drug. Plasma concentrations of this metabolite are approximately 40% of those seen for sildenafil, so that the metabolite accounts for about 20% of sildenafil's pharmacologic effects. Geriatrics: Healthy elderly volunteers (65 years or over) had a

1. Indications and Usage for Sildenafil Tablets

There was one subject with a decrease from baseline in standing systolic BP >30mmHg following VIAGRA 50 mg and one subject with a decrease from baseline in standing systolic BP > 30 mmHg following both VIAGRA 50 mg and placebo. There were no severe adverse events potentially related to blood pressure and no episodes of syncope reported in this study. In 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. In dose period 1, subjects were administered open-label doxazosin and a single dose of VIAGRA 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.

How Sildenafil Works to Treat ED

Subjects who had successfully completed the previous doxazosin interaction study (using VIAGRA chew 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, VIAGRA 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. 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. reduced clearance of sildenafil, resulting

5.4 Visual Loss

Even though this total dosage produced plasma sildenafil concentrations which were approximately 2 to 5 times higher than the mean maximum plasma concentrations following a single oral dose of 100 mg in healthy male volunteers, the hemodynamic response to exercise was preserved in these patients. In a double-blind study, 144 patients with erectile dysfunction and chronic stable angina limited by exercise, not receiving chronic oral nitrates, were randomized to a single dose of placebo or VIAGRA 100 mg 1 hour prior to exercise testing. The primary endpoint was time to limiting angina in the evaluable cohort. The mean times (adjusted for baseline) to onset of limiting angina were 423.6 sildenafil price ireland and 403.7 seconds for sildenafil (N=70) and placebo, respectively. These results demonstrated that the effect of VIAGRA on the primary endpoint was statistically non-inferior to placebo.

Warnings for other groups

Effects of VIAGRA on Vision: At single oral doses of 100 mg and 200 mg, transient dose-related impairment of color discrimination was detected using the Farnsworth-Munsell 100-hue test, with peak effects near the time of peak plasma levels. Subjects in the study reported this finding as difficulties in discriminating blue/green. An evaluation of visual function at doses up to twice the maximum recommended dose revealed no effects of VIAGRA on visual acuity, intraocular pressure, or pupillometry. VIAGRA is rapidly absorbed after oral administration, with a mean absolute bioavailability of 41% (range 25–63%). The pharmacokinetics of sildenafil are dose-proportional over the recommended dose range. in approximately 84% and 107% higher

5.3 Epistaxis

In 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. Following at least 14 consecutive days of doxazosin, VIAGRA 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 VIAGRA 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 VIAGRA 50 mg.

13.1 Carcinogenesis & Mutagenesis & Impairment of Fertility

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 Baseline Blood pressure was measured after administration of VIAGRA at the same times as those specified for the first doxazosin study. There were two subjects who had a standing SBP of < 85 mmHg. In these two subjects, hypotension was reported as a moderately severe adverse event, beginning at approximately 1 hour after administration of VIAGRA 50 mg and resolving after approximately 7.5 hours. plasma AUC values of sildenafil and its active N-desmethyl metabolite,

• The societal impact of sildenafil has been profound since its introduction.
• It helped destigmatize the discussion and treatment of erectile dysfunction.
• It spawned a multi-billion dollar market for sexual health pharmaceuticals.
• The "Viagra" brand name became one of the most recognized in the world.
• It led to increased research and development in urology and sexual medicine.
• It also raised important questions about medicalization and lifestyle drugs.
• Direct-to-consumer advertising for ED treatments became widespread.
• It prompted debates about insurance coverage for quality-of-life medications.
• The success of sildenafil accelerated research into other PDE5 inhibitors.
• It highlighted the importance of serendipity in drug discovery.
• Its impact extends beyond medicine into cultural and social spheres.

respectively, compared to those seen

Warnings & Precautions

The maximum observed decrease in systolic blood pressure was -18.5 mmHg when sildenafil was co-administered with alcohol versus -17.4 mmHg when alcohol was administered alone. The maximum observed decrease in diastolic blood pressure was -17.2 mmHg when sildenafil was co-administered with alcohol versus -11.1 mmHg when alcohol was administered alone. There were no reports of postural dizziness or orthostatic hypotension. The maximum recommended dose of 100 mg sildenafil was not evaluated in this study [see Drug Interactions (7.5)]. Effects of VIAGRA on Cardiac Parameters: Single oral doses of sildenafil up to 100 mg produced no clinically relevant changes in the ECGs of normal male volunteers.

5.8 Effects on Bleeding

Studies have produced relevant data on the effects of VIAGRA on cardiac output. In one small, open-label, uncontrolled, pilot study, eight patients with stable ischemic heart disease underwent Swan-Ganz catheterization. A total dose of 40 mg sildenafil was administered by four intravenous infusions. The results from this pilot study are shown in Table 3; the mean resting systolic and diastolic blood pressures decreased by 7% and 10% compared to baseline in these patients. Mean resting values for right atrial pressure, pulmonary artery pressure, pulmonary artery occluded pressure and cardiac output decreased by 28%, 28%, 20% and 7% respectively. in healthy younger volunteers (18–45 years).

More about sildenafil

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 Baseline Blood pressure was measured after administration of VIAGRA at the same times as those specified for the previous doxazosin studies. There were three subjects who had a standing SBP of < 85 mmHg. All three were taking VIAGRA 100 mg, and all three reported mild adverse events at the time of reductions in standing SBP, including vasodilation and lightheadedness.

8.1 Pregnancy: Teratogenic effects

There were four subjects with a decrease from baseline in standing systolic BP > 30 mmHg following VIAGRA 100 mg, one subject with a decrease from baseline in standing systolic BP > 30 mmHg following placebo and one subject with a decrease from baseline in standing systolic BP > 30 mmHg following both VIAGRA and placebo. While there were no severe adverse events potentially related to blood pressure reported in this study, one subject reported moderate vasodilatation after both VIAGRA 50 mg and 100 mg. There were no episodes of syncope reported in this study. Effect of VIAGRA on Blood Pressure When Co-administered with Anti-hypertensives: When VIAGRA 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. Effect of VIAGRA on Blood Pressure When Co-administered with Alcohol: VIAGRA (50 mg) did not potentiate the hypotensive effect of alcohol (0.5 g/kg) in healthy volunteers with mean maximum blood alcohol levels of 0.08%.