Sapropterin: (Moderate) Sapropterin acts as a cofactor in the synthesis of nitric oxide and may cause vasorelaxation.
| Point | Explanation | Importance |
|---|---|---|
| Take on an empty stomach or after light meal | Food, especially high-fat meals, delays onset | Ensures faster effectiveness |
| Do not exceed recommended dose | Overdose increases side effects and risks | Safety |
| Timing of administration | 30-60 minutes before sexual activity | Optimal results |
| Potential side effects | Headache, flushing, vision changes | Recognize and report unusual effects |
| Avoid alcohol consumption | Can decrease efficacy and increase side effects | Safety |
Caution should be exercised when administering sapropterin in combination with drugs that affect nitric oxide-mediated vasorelaxation such as phosphodiesterase inhibitors.
Why is this medication prescribed?
Discontinue riociguat at least 24 hours prior to sildenafil administration and do not administer within 24 hours of sildenafil. Monitor for signs and symptoms of hypotension during transition of therapy. PDE5 inhibitors, including sildenafil, may potentiate the hypotensive effects of riociguat. Ritlecitinib: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with ritlecitinib is necessary; consider a starting dose of 25 mg of sildenafil when prescribed for erectile dysfunction. Ritonavir: (Major) Coadministration of ritonavir is contraindicated in patients receiving sildenafil for pulmonary arterial hypertension (PAH). When given together these agents may produce an additive reduction in blood pressure.
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The combination of sapropterin and a phosphodiesterase (PDE5) inhibitor did not significantly reduce blood pressure when administered concomitantly in animal studies.
12.2 Pharmacodynamics
The patient should be monitored carefully and the dosage should be adjusted based on clinical response. For example, in patients whose hypertension was controlled with nifedipine, vardenafil produced mean additional supine systolic/diastolic blood pressure reductions of 3 to 4 mmHg (age group 65 to 69 years) and 5 to 6 mmHg (age group 70 to 80 years) compared to placebo. Nilotinib: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with nilotinib is necessary; a dose reduction of sildenafil may be necessary when prescribed for erectile dysfunction. Nirmatrelvir; Ritonavir: (Major) Coadministration of ritonavir is contraindicated in patients receiving sildenafil for pulmonary arterial hypertension (PAH). (Major) Concomitant use of ritonavir-boosted nirmatrelvir and sildenafil, when used for pulmonary arterial hypertension (PAH), is contraindicated; consider an alternative COVID-19 therapy.
Alcohol interaction warning
Consider withholding sildenafil, when used for erectile dysfunction, during concomitant receipt of ritonavir-boosted nirmatrelvir. Coadministration may increase sildenafil exposure resulting in increased toxicity. Nitrates: (Contraindicated) Coadministration of phosphodiesterase inhibitors with organic nitrates or nitrites in any dosage formulation is contraindicated. Nitroglycerin: (Contraindicated) Coadministration of phosphodiesterase inhibitors with organic nitrates or nitrites in any dosage formulation is contraindicated. Nitroprusside: (Contraindicated) Concomitant use of nitroprusside and sildenafil is contraindicated due to the risk of additive hypotension.
How can I tell if Viagra’s not working?
If the patient has taken sildenafil, at least 24 hours must elapse before nitroprusside administration is considered; monitor hemodynamics closely. In addition, sildenafil may potentiate the nitric oxide-mediated platelet anti-aggregatory effect of nitroprusside. Odevixibat: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with odevixibat is necessary as concurrent use may decrease sildenafil exposure. Olmesartan; Amlodipine; Hydrochlorothiazide, HCTZ: (Moderate) Monitor for additive hypotension if amlodipine is administered concurrently with sildenafil, as both agents act independently to reduce blood pressure. Olutasidenib: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration sildenafil citrate 150 mg red pill with olutasidenib is necessary as concurrent use may decrease sildenafil exposure. The additive effect of these agents has not been studied in humans.
- Sildenafil interacts with nitrates, causing dangerous blood pressure drops.
- Consult a doctor before starting if on other medications.
- Alcohol may reduce the effectiveness and increase side effects.
Saquinavir: (Major) Sildenafil is contraindicated for use with saquinavir when used for pulmonary arterial hypertension (PAH).
- Typical sildenafil dose ranges from 25 to 100 mg.
- It should be taken 30-60 minutes before activity.
- Do not exceed one dose within 24 hours.
Coadministration of saquinavir increased the sildenafil AUC by about 3-fold in a drug interaction study.
What is sildenafil?
When sildenafil is used for erectile dysfunction, consider a starting dose blue sildenafil of 25 mg for patients receiving posaconazole. Prazosin: (Moderate) Due to the potential for symptomatic hypotension, patients should be stable on alpha-blocker therapy before initiating therapy with the lowest dose of sildenafil. Promethazine; Phenylephrine: (Minor) The therapeutic effect of phenylephrine injection may be decreased in patients receiving phosphodiesterase inhibitors. Quinidine: (Moderate) Sildenafil is metabolized principally by the hepatic isoenzymes CYP3A4 and CYP2C9. Quinine: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with quinine is necessary; a dose reduction of sildenafil may be necessary when prescribed for erectile dysfunction.
When to call your doctor
Ranolazine: (Moderate) Sildenafil is metabolized principally by the hepatic CYP3A4 (major route) and 2C9 (minor route) isoenzymes. Inhibitors of these isoenzymes may reduce sildenafil clearance. The manufacturer recommends dosage reduction in patients receiving potent cytochrome CYP3A4 inhibitors. Population data from patients in clinical trials did indicate a reduction in sildenafil clearance when it was coadministered with CYP3A4 inhibitors. Rasagiline: (Moderate) Additive hypotensive effects may be seen when monoamine oxidase inhibitors (MAOIs) are combined with antihypertensives or medications with hypotensive properties.
Risk Summary
Careful monitoring of blood pressure is suggested during concurrent therapy of MAOIs with vasodilators. Patients should be instructed to rise slowly from a sitting position, and to report syncope or changes in blood pressure or heart rate to their health care provider. Ribociclib: (Major) Coadministration with ribociclib is not recommended in patients receiving sildenafil for pulmonary arterial hypertension (PAH). When sildenafil is used for erectile dysfunction, consider a starting dose of 25 mg for patients receiving ribociclib. Ribociclib; Letrozole: (Major) Coadministration with ribociclib is not recommended in patients receiving sildenafil for pulmonary arterial hypertension (PAH). Silodosin: (Moderate) Due to the potential for symptomatic hypotension, patients should be stable on silodosin therapy before initiating therapy with the lowest dose of sildenafil.
| Study | Population Sample | Improvement Rate | Onset Time | Notes |
|---|---|---|---|---|
| Phase III Trial A | 500 men with ED | 85% reported improvement | 30-60 min | Compared with placebo |
| Phase III Trial B | 300 women (off-label use) | Variable, limited evidence | N/A | Under investigation for other indications |
| Post-marketing Data | 10,000+ patients | 80-90% efficacy reported | Varies | Real-world effectiveness observations |
Conversely, patients already receiving an optimized dose of sildenafil should be started on the lowest dose of silodosin; increases in the alpha-blocker dose should be done in a stepwise fashion.
5.2 Prolonged Erection and Priapism
Rifabutin: (Minor) Sildenafil is metabolized principally by cytochrome P450 3A4 and 2C9 enzymes. Rifampin: (Minor) Sildenafil is sildenafil generic metabolized principally by cytochrome P450 3A4 and 2C9 enzymes. Rifapentine: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with rifapentine is necessary as concurrent use may decrease sildenafil exposure. Concomitant administration of strong CYP3A4 inducers is expected to substantially decrease plasma concentrations of sildenafil. Riociguat: (Contraindicated) Use of riociguat and sildenafil is contraindicated due to the risk of hypotension. Other variables, such as intravascular volume depletion, concurrent antihypertensive therapy, or evidence of hemodynamic instability with alpha-blocker monotherapy, may affect the safety of concomitant use of sildenafil and silodosin.
- Sildenafil citrate is used to treat erectile dysfunction.
- It enhances blood flow to the penis for a stronger erection.
- Commonly available in tablet form for oral use.
Sodium Phenylbutyrate; Taurursodiol: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with taurursodiol is necessary as concurrent use may decrease sildenafil exposure.
2.4 Dosage Adjustments Due to Drug Interactions
Omaveloxolone: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with omaveloxolone is necessary as concurrent use may decrease sildenafil exposure. It can be expected that concomitant administration of CYP3A4 enzyme-inducers, such as rifabutin, will decrease plasma levels of sildenafil, however, no interaction studies have been performed. Oritavancin: (Moderate) Coadministration of oritavancin and sildenafil may result in increases or decreases in sildenafil exposure and may increase side effects or decrease efficacy of sildenafil. Sildenafil is primarily metabolized by CYP3A4, but is also metabolized by CYP2C9. Oritavancin weakly induces CYP3A4, while weakly inhibiting CYP2C9.
Does Viagra prevent ejaculation?
If these drugs are administered concurrently, monitor the patient for signs of toxicity or lack of efficacy. Coadministration of pazopanib and sildenafil, a CYP3A4 substrate, may cause an increase in systemic concentrations of sildenafil. Use caution when administering these drugs concomitantly. Perindopril; Amlodipine: (Moderate) Monitor for additive hypotension if amlodipine is administered concurrently with sildenafil, as both agents act independently to reduce blood pressure. Pexidartinib: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with pexidartinib is necessary as concurrent use may decrease sildenafil exposure.
Administration Notes
Phenelzine: (Moderate) Additive hypotensive effects may be seen when monoamine oxidase inhibitors (MAOIs) are combined with sildenafil. Phenoxybenzamine: (Moderate) Due to the potential for symptomatic hypotension, patients should be stable on alpha-blocker therapy before initiating therapy with the lowest dose of sildenafil. Phentolamine: (Moderate) Due to the potential for symptomatic hypotension, patients should be stable on alpha-blocker therapy before initiating therapy with the lowest dose of sildenafil. Phenylephrine: (Minor) The therapeutic effect of phenylephrine injection may be decreased in patients receiving phosphodiesterase inhibitors. Posaconazole: (Major) Coadministration of posaconazole is not recommended in patients receiving sildenafil for pulmonary arterial hypertension (PAH). Sotorasib: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with sotorasib is necessary as concurrent use may decrease sildenafil exposure.
- Sildenafil is not an aphrodisiac and needs sexual stimulation.
- It does not increase libido directly.
- Effectiveness varies between individuals.
St. John's Wort, Hypericum perforatum: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with St. John's Wort is necessary as concurrent use may decrease sildenafil exposure.
| Common Side Effect | Frequency | Severity | Notes |
|---|---|---|---|
| Headache | Very common | Mild to moderate | Usually transient |
| Flushing | Common | Mild | Often resolves quickly |
| Dyspepsia / Indigestion | Common | Mild | Can be managed with antacids |
| Visual Disturbances | Less common | Mild | Changes in color perception |
| Priapism | Rare | Serious | Medical emergency, requires immediate attention |