How Sildenafil Citrate Works in the Body
Nesiritide, BNP: (Major) No formal drug interaction trials have been conducted with nesiritide.
| Brand Name | Manufacturer | Formulation Type | Typical Dosage | Notes |
|---|---|---|---|---|
| Viagra | Pfizer | Tablet | 25, 50, 100 mg | Most well-known brand |
| Revatio | Pfizer | Tablet | 20 mg | For pulmonary hypertension |
| Sildenafil Citrate | Various generic manufacturers | Tablet | 25, 50, 100 mg | Generic versions available |
| Kamagra | Ajanta Pharma | Oral Gel | 100 mg | Used off-label in some countries |
Sildenafil use within 24 hours was an exclusion criteria for nesiritide treatment during clinical trials.
Medical Conditions Treated with Sildenafil
Levoketoconazole: (Major) Coadministration of ketoconazole is not recommended in patients receiving sildenafil for pulmonary arterial hypertension (PAH). Lonafarnib: (Major) Coadministration with lonafarnib 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 lonafarnib. Lopinavir; Ritonavir: (Major) Coadministration of ritonavir is contraindicated in patients receiving sildenafil for pulmonary arterial hypertension (PAH). Concurrent use substantially increases the sildenafil plasma concentrations and may result in increased associated adverse events including hypotension, syncope, visual changes, and prolonged erection.
Incidence not known
Ritonavir, a strong CYP3A4 inhibitor, increased the AUC of sildenafil, a sensitive CYP3A4 substrate, by 11-fold in a drug interaction study. Lorcaserin: (Moderate) Lorcaserin is a serotonin 2C receptor agonist, and priapism is a potential effect of 5-HT2C receptor agonism. Because there is little experience with the combination of lorcaserin and medications indicated for erectile dysfunction (e.g., phosphodiesterase inhibitors), combined use should be approached with caution. Lorlatinib: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with lorlatinib is necessary as concurrent use may decrease sildenafil exposure. Lumacaftor; Ivacaftor: (Moderate) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as sildenafil. Although not identified during clinical trials, the potential for symptomatic hypotension may be significantly increased when coadministering nesiritide with sildenafil.
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Sildenafil should be avoided within 24 hours before or after nesiritide use. Netupitant, Fosnetupitant; Palonosetron: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with netupitant; palonosetron is necessary; a dose reduction of sildenafil may be necessary when prescribed for erectile dysfunction.
What other information should I know?
Itraconazole: (Major) Avoid use of sildenafil for the treatment of pulmonary hypertension during and for 2 weeks after discontinuation of itraconazole treatment. When sildenafil is used for erectile dysfunction, consider a starting dose of 25 mg for patients receiving itraconazole. Ivacaftor: (Moderate) Increased monitoring is recommended if ivacaftor is administered concurrently with CYP2C9 substrates, such as sildenafil. Ivosidenib: (Moderate) Monitor for loss of efficacy of sildenafil during coadministration of ivosidenib; a sildenafil dose adjustment may be necessary. Sildenafil is a sensitive substrate of CYP3A4; ivosidenib induces CYP3A4 and may lead to decreased sildenafil concentrations.
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Ketoconazole: (Major) Coadministration of ketoconazole 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 ketoconazole. Lansoprazole; Amoxicillin; Clarithromycin: (Major) Coadministration of clarithromycin is not recommended in patients receiving sildenafil for pulmonary arterial hypertension (PAH). Lefamulin: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with oral lefamulin is necessary; consider a starting dose of 25 mg of sildenafil when prescribed for erectile dysfunction. Sildenafil is a sensitive CYP3A4 substrate and oral lefamulin is a moderate CYP3A4 inhibitor; an interaction is not expected with intravenous lefamulin. Nevirapine: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with nevirapine is necessary as concurrent use may decrease sildenafil exposure.
More about sildenafil
Lenacapavir: (Moderate) Monitor for an increase in sildenafil-related adverse reactions if coadministration with lenacapavir is necessary; consider a starting dose of 25 mg of sildenafil when prescribed for erectile dysfunction. Sildenafil is a sensitive CYP3A substrate and lenacapavir is a moderate CYP3A inhibitor. In a drug interaction study, coadministration with a moderate CYP3A inhibitor increased the AUC of sildenafil by 182%. Lesinurad: (Moderate) Lesinurad may decrease the systemic exposure and therapeutic efficacy of sildenafil; monitor for potential reduction in efficacy. Lesinurad; sildenafil tablet manforce 50 mg Allopurinol: (Moderate) Lesinurad may decrease the systemic exposure and therapeutic efficacy of sildenafil; monitor for potential reduction in efficacy.
Is there a “female Viagra”?
Letermovir: (Major) Monitor for an increase in sildenafil-related adverse reactions if coadministration with letermovir is necessary; a dose reduction of sildenafil may be necessary when prescribed for erectile dysfunction. Concurrent use is not recommended in patients receiving sildenafil for pulmonary arterial hypertension and taking cyclosporine, because the magnitude of the interaction may be amplified. Consider a starting dose of 25 mg of sildenafil for erectile dysfunction in patients receiving letermovir with cyclosporine. Letermovir is a moderate CYP3A4 inhibitor; however, when given with cyclosporine, the combined effect on CYP3A4 substrates is similar to a strong CYP3A4 inhibitor. Levamlodipine: (Moderate) Monitor for additive hypotension if amlodipine is administered concurrently with sildenafil, as both agents act independently to reduce blood pressure. Sildenafil is a sensitive CYP3A substrate and nevirapine is sildenafil citrate tablets for female a weak CYP3A inducer. Nicardipine: (Moderate) Nicardipine is an inhibitor of CYP3A4 isoenzymes.
- Sildenafil is available in most countries through prescription only.
- It is used worldwide, with varying approval statuses.
- FDA and EMA have rigorous testing standards for sildenafil.
- Using the drug responsibly can lead to successful treatment outcomes.
- Combining sildenafil with other medications requires medical supervision.
- Be aware of the potential for drug interactions with heart or blood pressure meds.
- Always consult a healthcare professional for personalized advice.
Co-administration with nicardipine may lead to an increase in serum levels of drugs that are CYP3A4 substrates, such as sildenafil.
Administration and Monitoring
Mobocertinib: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with mobocertinib is necessary as concurrent use may decrease sildenafil exposure. Monoamine oxidase inhibitors: (Moderate) Additive hypotensive effects may be seen when monoamine oxidase inhibitors (MAOIs) are combined with sildenafil. Nebivolol: (Moderate) Monitor closely for decreased efficacy of either drug if sildenafil is coadministered with nebivolol. The AUC of sildenafil was decreased by 21% when coadministered with nebivolol. A similar decrease in the concentration of d-nebivolol (less than 20% in the AUC) was also observed with coadministration of sildenafil.
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Nebivolol; Valsartan: (Moderate) Monitor closely for decreased efficacy of either drug if sildenafil is coadministered with nebivolol. Nefazodone: (Major) Coadministration of nefazodone 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 nefazodone. Nelfinavir: (Major) Sildenafil is contraindicated for use with nelfinavir when used for pulmonary arterial hypertension (PAH). Sildenafil is a sensitive CYP3A4 substrate; nelfinavir is a strong CYP3A4 inhibitor. Nifedipine: (Moderate) Nifedipine can have additive hypotensive effects when administered with phosphodiesterase inhibitors (PDE 5 inhibitors).
Ongoing Research and Future Applications
If concurrent use of lurasidone and antihypertensive agents is necessary, patients should be counseled on measures to prevent orthostatic hypotension, such as sitting on the edge of the bed for several minutes prior to standing in the morning and rising slowly from a seated position. Close monitoring of blood pressure is recommended until the full effects of the combination therapy are known. Mavacamten: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with mavacamten is necessary as concurrent use may decrease sildenafil exposure. Mifepristone: (Major) Coadministration with mifepristone is not recommended in patients receiving sildenafil citrate tablets 150 mg sildenafil for pulmonary arterial hypertension (PAH). When sildenafil is used for erectile dysfunction, consider a starting dose of 25 mg for patients receiving mifepristone.
Platelet-aggregation Inhibitors
Sildenafil is a sensitive CYP3A substrate and mifepristone is a strong CYP3A inhibitor. Mitapivat: (Moderate) Monitor for decreased efficacy of sildenafil if coadministration with mitapivat is necessary as concurrent use may decrease sildenafil exposure. Mitotane: (Major) Use caution if mitotane and sildenafil are used concomitantly, and monitor for decreased efficacy of sildenafil and a possible change in dosage requirements. Mitotane is a strong CYP3A4 inducer and sildenafil is a CYP3A4 substrate; coadministration may result in decreased plasma concentrations of sildenafil. Population pharmacokinetic analysis of data from patients in clinical trials indicated approximately 3-fold the sildenafil clearance when it was co-administered with mild CYP3A inducers. 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.
- Sildenafil can enhance the effects of other blood pressure medications.
- The drug’s safety profile is well-studied with many clinical trials.
- Cardiovascular health is an important consideration when taking sildenafil.
- Long-term use requires monitoring for adverse reactions.
- Patient education helps reduce risks and optimize dosage.
- Generic sildenafil offers a cost-effective alternative to branded Viagra.
- Regular health assessments can ensure safe usage.
Consider withholding sildenafil, when used for erectile dysfunction, during concomitant receipt of ritonavir-boosted nirmatrelvir.
| Contraindication | Explanation | Severity Level | Notes |
|---|---|---|---|
| Nitrates use | Can cause severe hypotension | Critical | Avoid concomitant use |
| Heart conditions | Risk of cardiovascular events | Moderate | Consult healthcare provider |
| Hypotension | Low blood pressure | Moderate | Use with caution |
| Retinal Disorders | Potential for vision impairment | Mild | Seek medical advice |