This is consistent with ritonavir’s marked effects on a broad range of P450 substrates. Sildenafil citrate had no effect on ritonavir pharmacokinetics [see Dosage and Administration (2.4) and Drug Interactions (7.4)].Although the interaction between other protease inhibitors and sildenafil has not been studied, their concomitant use is expected to increase sildenafil levels.In a study of healthy male volunteers, co-administration of sildenafil at steady state (80 mg t.i.d.) with endothelin receptor antagonist bosentan (a moderate inducer of CYP3A4, CYP2C9 and possibly of CYP2C19) at steady state (125 mg b.i.d.) resulted in a 63% decrease of sildenafil AUC and a 55% decrease in sildenafil Cmax. Concomitant administration of strong CYP3A4 inducers, such as rifampin, is expected to cause greater decreases in plasma levels of sildenafil.Single doses of antacid (magnesium hydroxide/aluminum hydroxide) did not affect the bioavailability of sildenafil citrate.In healthy male volunteers, there was no evidence of a clinically significant effect of azithromycin (500 mg daily for 3 days) on the systemic exposure of sildenafil or its major circulating metabolite.Pharmacokinetic data from patients in clinical trials showed no effect on sildenafil pharmacokinetics of CYP2C9 inhibitors (such as tolbutamide, warfarin), CYP2D6 inhibitors (such as selective serotonin reuptake inhibitors, tricyclic antidepressants), thiazide and related diuretics, ACE inhibitors, and calcium channel blockers.
| Contraindication | Explanation | Alternative Action |
|---|---|---|
| Use with Nitrates | Risk of severe hypotension | Avoid combined use |
| Severe Liver Impairment | Reduced metabolism, increased side effects | Consult healthcare provider |
| Hypotension (<90/60 mm Hg) | Sildenafil can lower blood pressure further | Monitor blood pressure before use |
| Recent Stroke or Heart Attack | Increased cardiovascular risk | Medical consultation prior to use |
| Allergic Reaction to Sildenafil | Risk of anaphylaxis | Discontinue use, seek medical advice |
The AUC of the active metabolite, N-desmethyl sildenafil, was increased 62% by loop and potassium-sparing diuretics and 102% by nonspecific beta-blockers. These effects on the metabolite are not expected to be of clinical consequence.Effects of sildenafil tablets on Other DrugsIn vitro studies:Sildenafil is a weak inhibitor of the CYP isoforms 1A2, 2C9, 2C19, 2D6, 2E1 and 3A4 (IC50 >150 μM).
8.5 Geriatric Use
This is consistent with ritonavir’s marked effects on a broad range of P450 substrates. Sildenafil citrate had no effect on ritonavir pharmacokinetics [see Dosage and Administration (2.4) and Drug Interactions (7.4)].Although the interaction between other protease inhibitors and sildenafil has not been studied, their concomitant use is expected to increase sildenafil levels.In a study of healthy male volunteers, co-administration of sildenafil at steady state (80 mg t.i.d.) with endothelin receptor antagonist bosentan (a moderate inducer of CYP3A4, CYP2C9 and possibly of CYP2C19) at steady state (125 mg b.i.d.) resulted in a 63% decrease of sildenafil AUC and a 55% decrease in sildenafil Cmax. Concomitant administration of strong CYP3A4 inducers, such as rifampin, is expected to cause greater decreases in plasma levels of sildenafil.Single doses of antacid (magnesium hydroxide/aluminum hydroxide) did not affect the bioavailability of sildenafil citrate.In healthy male volunteers, there was no evidence of a clinically significant effect of azithromycin (500 mg daily for 3 days) on the systemic exposure of sildenafil or its major circulating metabolite.Pharmacokinetic data from patients in clinical trials showed no effect on sildenafil pharmacokinetics of CYP2C9 inhibitors (such as tolbutamide, warfarin), CYP2D6 inhibitors (such as selective serotonin reuptake inhibitors, tricyclic antidepressants), thiazide and related diuretics, ACE inhibitors, and calcium channel blockers. The AUC of the active metabolite, N-desmethyl sildenafil, was increased 62% by loop and potassium-sparing diuretics and 102% by nonspecific beta-blockers. These effects on the metabolite are not expected to be of clinical consequence.Effects of sildenafil tablets on Other DrugsIn vitro studies:Sildenafil is a weak inhibitor of the CYP isoforms 1A2, 2C9, 2C19, 2D6, 2E1 and 3A4 (IC50 >150 μM).
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Given sildenafil peak plasma concentrations of approximately 1 μM after recommended doses, it is unlikely that sildenafil citrate will alter the clearance of substrates of these isoenzymes.In vivo studies:No significant interactions were shown with tolbutamide (250 mg) or warfarin (40 mg), both of which are metabolized by CYP2C9.In a study of healthy male volunteers, sildenafil (100 mg) did not affect the steady state pharmacokinetics of the HIV protease inhibitors, saquinavir and ritonavir, both of which are CYP3A4 substrates.Sildenafil citrate (50 mg) did not potentiate the increase in bleeding time caused by aspirin (150 mg).Sildenafil at steady state, at a dose not approved for the treatment of erectile dysfunction (80 mg t.i.d.) resulted in a 50% increase in AUC and a 42% increase in Cmax of bosentan (125 mg b.i.d.). 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. Sildenafil at recommended doses has no effect in the absence of sexual stimulation. 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.
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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 sildenafil tablets 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 tablets 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 sildenafil cenforce 2 hours. Effects of sildenafil tablets 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)]. Given sildenafil peak plasma concentrations of approximately 1 μM after recommended doses, it is unlikely that sildenafil citrate will alter the clearance of substrates of these isoenzymes.In vivo studies:No significant interactions were shown with tolbutamide (250 mg) or warfarin (40 mg), both of which are metabolized by CYP2C9.In a study of healthy male volunteers, sildenafil (100 mg) did not affect the steady state pharmacokinetics of the HIV protease inhibitors, saquinavir and ritonavir, both of which are CYP3A4 substrates.Sildenafil citrate (50 mg) did not potentiate the increase in bleeding time caused by aspirin (150 mg).Sildenafil at steady state, at a dose not approved for the treatment of erectile dysfunction (80 mg t.i.d.) resulted in a 50% increase in AUC and a 42% increase in Cmax of bosentan (125 mg b.i.d.). 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. Sildenafil at recommended doses has no effect in the absence of sexual stimulation. 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.
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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.
8.4 Pediatric Use
Missed Dose
Other Medical Problems
Effects of sildenafil tablets 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 tablets 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 sildenafil cenforce 2 hours.
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There were no episodes of syncope reported in this study. Effect of sildenafil tablets on Blood Pressure When Co-administered with Anti-hypertensives: When sildenafil tablets 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 sildenafil tablets on Blood Pressure When Co-administered with Alcohol: Sildenafil tablets (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%. The maximum recommended dose of 100 mg sildenafil was not evaluated in this study [see Drug Interactions (7.5)]. Effects of sildenafil tablets on Cardiac Parameters: Single oral doses of sildenafil up to 100 mg produced no clinically relevant changes in the ECGs of normal male volunteers.
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Studies have produced relevant data on the effects of sildenafil citrate on cardiac output. 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. 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 sildenafil tablets 100 mg 1 hour prior to exercise testing.
3. Shelf-life, Storage, and Dosage Form
Effects of sildenafil tablets 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)].
- Hearing loss associated with high-dose sildenafil is rare but reported.
- Tinnitus or ringing in the ears can occur shortly after taking 200mg.
- The mechanism may involve altered cochlear blood flow or oxidative stress.
- Symptoms usually resolve after discontinuation of the medication.
- Patients with preexisting hearing problems should exercise caution.
- Combining with ototoxic drugs (e.g., aspirin, NSAIDs) increases risk.
- Sudden sensorineural hearing loss requires urgent ENT evaluation.
- No evidence that regular use of standard doses causes permanent damage.
- At 200mg, the risk-benefit ratio for hearing should be individually assessed.
Effects of sildenafil tablets 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 sildenafil tablets 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 tablets with doxazosin, an alpha-adrenergic blocking agent. For the 17 subjects who received sildenafil tablets 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 tablets or matching placebo are shown in Figure 2. Figure 2: Mean Standing Systolic Blood Pressure Change from Baseline Of the four subjects who received sildenafil tablets 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 tablets 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.
12.1 Mechanism of Action
Twenty subjects received sildenafil tablets 50 mg, but only 19 subjects received matching placebo. This patient had been taking minoxidil, a potent sildenafil 20 mg tablets vasodilator, during the study. For the 19 subjects who received both sildenafil tablets 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 tablets or matching placebo are shown in Figure 3. Blood pressure was measured after administration of sildenafil tablets at the same times as those specified for the first doxazosin study.
- 200mg sildenafil should never be used without a doctor's prescription.
- A full medical history, including cardiac and eye status, is essential.
- Baseline blood pressure and liver/kidney function tests may be required.
- The physician must weigh benefits against risks of high-dose therapy.
- Patients should be educated on recognizing priapism and seeking help.
- Regular follow-up appointments are needed to monitor side effects.
- Do not share medication; doses are personalized to individual health.
- Avoid buying 200mg online from unlicensed sources; risk of fakes.
- Keep a record of all medications and supplements to prevent interactions.
There were no severe adverse events potentially related to blood pressure and no episodes of syncope reported in this study. 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 tablets 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 tablets 50 mg). For sildenafil tablet manforce 50 mg the 20 subjects who received sildenafil tablets 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 tablets or matching placebo are shown in Figure 4. Blood pressure was measured after administration of sildenafil tablets at the same times as those specified for the previous doxazosin studies.
4.1 Nitrates
There were no episodes of syncope reported in this study. Effect of sildenafil tablets on Blood Pressure When Co-administered with Anti-hypertensives: When sildenafil tablets 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 sildenafil tablets on Blood Pressure When Co-administered with Alcohol: Sildenafil tablets (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%.
Warnings & Precautions
Effects of sildenafil tablets 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 sildenafil tablets 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 tablets with doxazosin, an alpha-adrenergic blocking agent. For the 17 subjects who received sildenafil tablets 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 tablets or matching placebo are shown in Figure 2. Figure 2: Mean Standing Systolic Blood Pressure Change from Baseline Of the four subjects who received sildenafil tablets 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 tablets 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).
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Both of these subjects were protocol violators, one due to a low baseline standing SBP, and the other due to baseline orthostatic hypotension. Twenty subjects received sildenafil tablets 50 mg, but only 19 subjects received matching placebo. This patient had been taking minoxidil, a potent sildenafil 20 mg tablets vasodilator, during the study. For the 19 subjects who received both sildenafil tablets 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 tablets or matching placebo are shown in Figure 3. Blood pressure was measured after administration of sildenafil tablets at the same times as those specified for the first doxazosin study.
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There were no severe adverse events potentially related to blood pressure and no episodes of syncope reported in this study. 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 tablets 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 tablets 50 mg). For sildenafil tablet manforce 50 mg the 20 subjects who received sildenafil tablets 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 tablets or matching placebo are shown in Figure 4. Blood pressure was measured after administration of sildenafil tablets at the same times as those specified for the previous doxazosin studies. The maximum recommended dose of 100 mg sildenafil was not evaluated in this study [see Drug Interactions (7.5)]. Effects of sildenafil tablets on Cardiac Parameters: Single oral doses of sildenafil up to 100 mg produced no clinically relevant changes in the ECGs of normal male volunteers. Studies have produced relevant data on the effects of sildenafil citrate on cardiac output. 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. 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 sildenafil tablets 100 mg 1 hour prior to exercise testing.
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