Bioequivalence and Bioavailability of an Orodispersible Tablet of Sildenafil Citrate in Healthy Chinese Male Subjects

[19] Inhibitors of these isoenzymes may reduce sildenafil clearance. Increased systemic exposure to sildenafil may result in an increase in sildenafil-induced adverse effects. The manufacturer recommends dosage reduction in patients receiving potent cytochrome CYP3A4 inhibitors.

Side Effects for Viagra

If possible, cimetidine use should be avoided in patients who take sildenafil. Etravirine is an inducer of CYP3A4; coadministration may result in decreased sildenafil concentrations. Dosage adjustments sildenafil citrate tablets 150 mg may be needed based on clinical efficacy. Particular caution should be used when prescribing phosphodiesterase type 5 (PDE5) inhibitors to patients receiving ritonavir. Coadministration of ritonavir with sildenafil results in an 11-fold increase of sildenafil AUC; one death has been reported in a patient who received sildenafil in combination with ritonavir and Fortovase.

What Are the Available Sildenafil Dosages?

[25] Substantially increased sildenafil plasma concentrations may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. If coadministered when sildenafil is used for erectile dysfunction, a reduced dose of sildenafil 25 mg every 48 hours with increased monitoring for adverse reactions is recommended. [26][27] When sildenafil is used for the treatment of pulmonary arterial hypertension (PAH), the use of ritonavir is contraindicated because a safe and effective dose has not been established. Particular caution should be used when prescribing phosphodiesterase type 5 (PDE5) inhibitors to patients receiving saquinavir. Sildenafil is contraindicated for use with the anti-retroviral protease inhibitors when used for pulmonary arterial hypertension (PAH).

Binding Characteristics

[28] If sildenafil is coadministered with saquinavir and used for erectile dysfunction, use sildenafil at reduced doses of 25 mg every 48 hours with increased monitoring for adverse reactions. [27][28] Coadministration of saquinavir, especially when ‘boosted’ with ritonavir, with PDE5 inhibitors is expected to substantially increase their plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. One death has been reported in a patient who received sildenafil in combination with ritonavir and saquinavir (Fortovase). Particular caution should be used when prescribing phosphodiesterase type 5 (PDE5) inhibitors to patients receiving amprenavir. Coadministration with sildenafil results in a 210% increase in sildenafil AUC. Consistent with its known effects on the nitric oxide/cGMP pathway, sildenafil was shown to potentiate the hypotensive effects of nitrates. Deaths have been reported in men who were using sildenafil while taking nitrate or nitrite therapy for angina. Sildenafil administration to patients who are concurrently using organic nitrates or nitrites in any form is contraindicated.

The safety and efficacy of tadalafil administered concurrently with any other phosphodiesterase (PDE5) inhibitors, such as sildenafil, has not been studied. The manufacturer of tadalafil recommends to avoid the use of tadalafil with any other PDE5 inhibitors. Coadministration of sildenafil, tadalafil or vardenafil and other organic nitrates has been shown to potentiate the hypotensive effects of nitrates; concomitant administration of these drugs for erectile dysfunction with nitrates is contraindicated. [20][22][23] Many methscopolamine-containing products list methscopolamine nitrate as the ingredient. Therefore, the concomitant use of sildenafil, tadalafil or vardenafil and products which contain methscopolamine nitrate is not recommended. Sildenafil is metabolized principally by cytochrome P450 (CYP) 3A4 (major route) and 2C9 (minor route) isoenzymes. Cimetidine is a known inhibitor of hepatic CYP enzymes and reduces the metabolism of sildenafil. Cimetidine (800 mg) caused a 56% increase in plasma sildenafil concentrations when coadministered with sildenafil 50 mg to healthy volunteers.

More about sildenafil

Lopinavir; ritonavir is contraindicated for use with sildenafil when sildenafil is used for the treatment of pulmonary arterial hypertension (PAH). [37] If coadministered when sildenafil is used for erectile dysfunction, use sildenafil at reduced doses of 25 mg every 48 hours with increased monitoring for adverse reactions. Particular caution should be used when prescribing phosphodiesterase type 5 (PDE5) inhibitors to patients receiving nelfinavir. [38] When sildenafil is coadministered with nelfinavir and used for erectile dysfunction, use sildenafil at reduced doses of 25 mg every 48 hours with increased monitoring for adverse reactions. [27][38] Coadministration of nelfinavir with PDE5 inhibitors is expected to substantially increase their plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Population data from patients in clinical trials also indicate a reduction in sildenafil clearance when it was coadministered with cimetidine. If possible, cimetidine use should be avoided in patients who take sildenafil. Etravirine is an inducer of CYP3A4; coadministration may result in decreased sildenafil concentrations.

2.3 Dosage Adjustments in Specific Situations

[29] If sildenafil is coadministered with amprenavir and used for erectile dysfunction, use sildenafil at reduced doses of 25 mg every 48 hours with increased monitoring for adverse reactions. [27][30] Substantially increased sildenafil plasma concentrations may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Particular caution should be used when prescribing phosphodiesterase type 5 (PDE5) inhibitors to patients receiving fosamprenavir. [29] If sildenafil is coadministered with fosamprenavir and used for erectile dysfunction, use sildenafil at reduced doses of 25 mg every 48 hours with increased monitoring for adverse reactions. [27][29] Coadministration with sildenafil results in a 210% increase in sildenafil AUC.

Does sildenafil interact with other medicines (drug interactions)?

Substantially increased sildenafil plasma concentrations may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Particular caution should be used when prescribing phosphodiesterase type 5 (PDE5) inhibitors to patients receiving atazanavir. [31] If sildenafil is coadministered with atazanavir and used for erectile dysfunction, use sildenafil at reduced doses of 25 mg every 48 hours with increased monitoring for adverse reactions. [27][31] Coadministration of atazanavir with PDE5 inhibitors is expected to substantially increase their plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Particular caution should be used when prescribing phosphodiesterase type 5 (PDE5) inhibitors to patients receiving darunavir.

What’s the difference between sildenafil 50 mg and 100 mg?

[32] When sildenafil is coadministered with darunavir and used for erectile dysfunction, use sildenafil at reduced doses of 25 mg every 48 hours with increased monitoring for adverse reactions. [27][32] Coadministration of darunavir with PDE5 inhibitors is expected to substantially increase their plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Sildenafil is contraindicated for use with cobicistat when used for pulmonary arterial hypertension (PAH). If used for erectile dysfunction, the dose of sildenafil should not exceed 25 mg every 48 sildenafil 50 mg tab hours with increased monitoring for adverse reactions during times of coadministration. Concurrent use is expected to substantially increase the sildenafil plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Dosage adjustments sildenafil citrate tablets 150 mg may be needed based on clinical efficacy. Particular caution should be used when prescribing phosphodiesterase type 5 (PDE5) inhibitors to patients receiving ritonavir. Coadministration of ritonavir with sildenafil results in an 11-fold increase of sildenafil AUC; one death has been reported in a patient who received sildenafil in combination with ritonavir and Fortovase. [25] Substantially increased sildenafil plasma concentrations may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. If coadministered when sildenafil is used for erectile dysfunction, a reduced dose of sildenafil 25 mg every 48 hours with increased monitoring for adverse reactions is recommended. [26][27] When sildenafil is used for the treatment of pulmonary arterial hypertension (PAH), the use of ritonavir is contraindicated because a safe and effective dose has not been established. Particular caution should be used when prescribing phosphodiesterase type 5 (PDE5) inhibitors to patients receiving saquinavir. Sildenafil is contraindicated for use with the anti-retroviral protease inhibitors when used for pulmonary arterial hypertension (PAH). [28] If sildenafil is coadministered with saquinavir and used for erectile dysfunction, use sildenafil at reduced doses of 25 mg every 48 hours with increased monitoring for adverse reactions. [27][28] Coadministration of saquinavir, especially when ‘boosted’ with ritonavir, with PDE5 inhibitors is expected to substantially increase their plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. One death has been reported in a patient who received sildenafil in combination with ritonavir and saquinavir (Fortovase). Particular caution should be used when prescribing phosphodiesterase type 5 (PDE5) inhibitors to patients receiving amprenavir.

5.1 Cardiovascular

Particular caution should be used when prescribing phosphodiesterase type 5 (PDE5) inhibitors to patients receiving tipranavir. [28] When sildenafil is coadministered with tipranavir and used for erectile dysfunction, use sildenafil at reduced doses of 25 mg every 48 hours with increased monitoring for adverse reactions. [27][28] Coadministration is expected to substantially increase the PDE5 inhibitor plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Coadministration with sildenafil results in a 210% increase in sildenafil AUC. [29] If sildenafil is coadministered with amprenavir and used for erectile dysfunction, use sildenafil at reduced doses of 25 mg every 48 hours with increased monitoring for adverse reactions. [27][30] Substantially increased sildenafil plasma concentrations may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Particular caution should be used when prescribing phosphodiesterase type 5 (PDE5) inhibitors to patients receiving fosamprenavir.

7.1 Nitrates

Sildenafil is contraindicated for use with atazanavir; cobicistat when used for pulmonary arterial hypertension (PAH). Sildenafil is contraindicated for use with darunavir; cobicistat when used for pulmonary arterial hypertension (PAH). Particular caution should be used when prescribing phosphodiesterase type 5 (PDE5) inhibitors to patients receiving indinavir. Additionally, sildenafil is contraindicated for use with the anti-retroviral protease inhibitors when used for pulmonary arterial hypertension (PAH).28731 When sildenafil is coadminstered with indinavir and used for erectile dysfunction, use sildenafil at reduced doses of 25 mg every 48 hours with increased monitoring for adverse reactions. [27] Substantially increased PDE5 inhibitor plasma concentrations are seen and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection.

5.7 Priapism

In a small pharmacokinetic study, the coadministration of a single dose of sildenafil (25 mg) to patients receiving indinavir (800 mg every 8 hours) resulted in markedly increased sildenafil AUC values (340% increase), as compared to historical controls. The Cmax for indinavir was increased by 48% and the 8-hour AUC was increased 11% following concurrent administration. In two of the six subjects, prolonged clinical effects of sildenafil were noted for 72 hours after a single dose of sildenafil. Particular caution should be used when prescribing phosphodiesterase type 5 (PDE5) inhibitors to patients receiving lopinavir; ritonavir (Kaletra). Coadministration of lopinavir; ritonavir (Kaletra) with these drugs is expected to substantially increase their plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. [29] If sildenafil is coadministered with fosamprenavir and used for erectile dysfunction, use sildenafil at reduced doses of 25 mg every 48 hours with increased monitoring for adverse reactions. [27][29] Coadministration with sildenafil results in a 210% increase in sildenafil AUC. Substantially increased sildenafil plasma concentrations may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Particular caution should be used when prescribing phosphodiesterase type 5 (PDE5) inhibitors to patients receiving atazanavir. [31] If sildenafil is coadministered with atazanavir and used for erectile dysfunction, use sildenafil at reduced doses of 25 mg every 48 hours with increased monitoring for adverse reactions. [27][31] Coadministration of atazanavir with PDE5 inhibitors is expected to substantially increase their plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Particular caution should be used when prescribing phosphodiesterase type 5 (PDE5) inhibitors to patients receiving darunavir.

• Sildenafil tablets 125 mg are generally well-tolerated.
• Seek medical attention if you experience vision changes.
• They are typically used on an as-needed basis.
• Avoid heavy meals before taking sildenafil to improve absorption.
• Sildenafil is not a cure for erectile dysfunction.
• Pregnant women should avoid sildenafil use.
• It is important to stay hydrated while using the medication.
• Follow specific instructions provided by your healthcare provider.

[32] When sildenafil is coadministered with darunavir and used for erectile dysfunction, use sildenafil at reduced doses of 25 mg every 48 hours with increased monitoring for adverse reactions. [27][32] Coadministration of darunavir with PDE5 inhibitors is expected to substantially increase their plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Sildenafil is contraindicated for use with cobicistat when used for pulmonary arterial hypertension (PAH). If used for erectile dysfunction, the dose of sildenafil should not exceed 25 mg every 48 sildenafil 50 mg tab hours with increased monitoring for adverse reactions during times of coadministration.

Concurrent use is expected to substantially increase the sildenafil plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection.

Warnings for Viagra

[19] Inhibitors of these isoenzymes may reduce sildenafil clearance. Increased systemic exposure to sildenafil may result in an increase in sildenafil-induced adverse effects. The manufacturer recommends dosage reduction in patients receiving potent cytochrome CYP3A4 inhibitors. Consistent with its known effects on the nitric oxide/cGMP pathway, sildenafil was shown to potentiate the hypotensive effects of nitrates. Deaths have been reported in men who were using sildenafil while taking nitrate or nitrite therapy for angina.

8.4 Pediatric Use

Sildenafil administration to patients who are concurrently using organic nitrates or nitrites in any form is contraindicated. The safety and efficacy of tadalafil administered concurrently with any other phosphodiesterase (PDE5) inhibitors, such as sildenafil, has not been studied. The manufacturer of tadalafil recommends to avoid the use of tadalafil with any other PDE5 inhibitors. Coadministration of sildenafil, tadalafil or vardenafil and other organic nitrates has been shown to potentiate the hypotensive effects of nitrates; concomitant administration of these drugs for erectile dysfunction with nitrates is contraindicated. [20][22][23] Many methscopolamine-containing products list methscopolamine nitrate as the ingredient.

Long-term use

Therefore, the concomitant use of sildenafil, tadalafil or vardenafil and products which contain methscopolamine nitrate is not recommended. Sildenafil is metabolized principally by cytochrome P450 (CYP) 3A4 (major route) and 2C9 (minor route) isoenzymes. Cimetidine is a known inhibitor of hepatic CYP enzymes and reduces the metabolism of sildenafil. Cimetidine (800 mg) caused a 56% increase in plasma sildenafil concentrations when coadministered with sildenafil 50 mg to healthy volunteers. Population data from patients in clinical trials also indicate a reduction in sildenafil clearance when it was coadministered with cimetidine. Sildenafil is contraindicated for use with atazanavir; cobicistat when used for pulmonary arterial hypertension (PAH). Sildenafil is contraindicated for use with darunavir; cobicistat when used for pulmonary arterial hypertension (PAH). Particular caution should be used when prescribing phosphodiesterase type 5 (PDE5) inhibitors to patients receiving indinavir.

Additionally, sildenafil is contraindicated for use with the anti-retroviral protease inhibitors when used for pulmonary arterial hypertension (PAH).28731 When sildenafil is coadminstered with indinavir and used for erectile dysfunction, use sildenafil at reduced doses of 25 mg every 48 hours with increased monitoring for adverse reactions. [27] Substantially increased PDE5 inhibitor plasma concentrations are seen and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. In a small pharmacokinetic study, the coadministration of a single dose of sildenafil (25 mg) to patients receiving indinavir (800 mg every 8 hours) resulted in markedly increased sildenafil AUC values (340% increase), as compared to historical controls.

• For best results, take sildenafil on an empty stomach.
• Eating fatty foods may delay its onset.
• The medication should be taken approximately 30 minutes before activity.
• Do not double dose to compensate for missed doses.
• Keep regular medical appointments during treatment.
• Report any worsening of symptoms to your doctor.
• Never use sildenafil if experiencing chest pain without medical guidance.
• Always follow the prescribed health regimen.

The Cmax for indinavir was increased by 48% and the 8-hour AUC was increased 11% following concurrent administration. In two of the six subjects, prolonged clinical effects of sildenafil were noted for 72 hours after a single dose of sildenafil. Particular caution should be used when prescribing phosphodiesterase type 5 (PDE5) inhibitors to patients receiving lopinavir; ritonavir (Kaletra). Coadministration of lopinavir; ritonavir (Kaletra) with these drugs is expected to substantially increase their plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection.

Lopinavir; ritonavir is contraindicated for use with sildenafil when sildenafil is used for the treatment of pulmonary arterial hypertension (PAH). [37] If coadministered when sildenafil is used for erectile dysfunction, use sildenafil at reduced doses of 25 mg every 48 hours with increased monitoring for adverse reactions. Particular caution should be used when prescribing phosphodiesterase type 5 (PDE5) inhibitors to patients receiving nelfinavir. [38] When sildenafil is coadministered with nelfinavir and used for erectile dysfunction, use sildenafil at reduced doses of 25 mg every 48 hours with increased monitoring for adverse reactions. [27][38] Coadministration of nelfinavir with PDE5 inhibitors is expected to substantially increase their plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection. Particular caution should be used when prescribing phosphodiesterase type 5 (PDE5) inhibitors to patients receiving tipranavir. [28] When sildenafil is coadministered with tipranavir and used for erectile dysfunction, use sildenafil at reduced doses of 25 mg every 48 hours with increased monitoring for adverse reactions. [27][28] Coadministration is expected to substantially increase the PDE5 inhibitor plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection.

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