Sildenafil (Viagra, Revatio)

Sildenafil (Viagra, Revatio) [∞]

Sildenafil (Viagra, Revatio)

Sildenafil is a phosphodiesterase type 5 (PDE5) inhibitor primarily used for erectile dysfunction (ED) and pulmonary arterial hypertension (PAH). It works by increasing blood flow to certain areas of the body.

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Alternate Names

• Viagra – Common brand name for erectile dysfunction treatment.
• Revatio – Brand name used for pulmonary arterial hypertension.
• PDE5 Inhibitor – Class of drugs to which sildenafil belongs.

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Chart of Uses

Use	Index
Erectile Dysfunction (ED)	{{ct: Erectile Dysfunction }}
Pulmonary Arterial Hypertension (PAH)	{{ct: Pulmonary Hypertension }}
Raynaud’s Phenomenon	{{ct: Raynaud’s Phenomenon }}
Altitude Sickness (Off-label)	{{ct: Altitude Sickness }}

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Warnings

• Cardiovascular Risks: Can cause a dangerous drop in blood pressure, especially when taken with nitrates.
• Vision Changes: May cause temporary vision disturbances, including blue-tinged vision.
• Hearing Loss: Sudden hearing loss has been reported in rare cases.
• Priapism (Prolonged Erection): May cause painful, prolonged erections requiring medical attention.
• Liver & Kidney Considerations: Should be used cautiously in patients with severe liver or kidney disease.
• Drug Interactions: Can interact with nitrates, alpha-blockers, and some antifungal and antibiotic medications.

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Active Compounds

• Sildenafil Citrate – The active ingredient responsible for PDE5 inhibition and increased blood flow.

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Natural Sources

Sildenafil is a synthetic compound and does not have direct natural sources. However, some natural substances are believed to have PDE5-inhibiting properties:

• Epimedium (Horny Goat Weed) – Contains icariin, which has PDE5 inhibition effects.
• Panax Ginseng – Traditionally used for sexual health, may have mild PDE5-like effects.
• Yohimbe (Pausinystalia yohimbe) – Contains yohimbine, a compound with vasodilatory effects.

Contraindications for Sildenafil and Tadalafil

Both sildenafil and tadalafil share similar contraindications due to their mechanism of action as PDE5 inhibitors, which affect blood pressure and cardiovascular function.

Absolute Contraindications (Do NOT use if any of these apply):

1. Use of Nitrates (e.g., nitroglycerin, isosorbide mononitrate/dinitrate)
   • Can cause a severe and life-threatening drop in blood pressure.
2. Severe Cardiovascular Disease
   • Unstable angina, recent heart attack (within the last 6 months), or severe heart failure.
3. Severe Hypotension (Low Blood Pressure)
   • Blood pressure lower than 90/50 mmHg.
4. Severe Liver Disease
   • Conditions such as cirrhosis or severe hepatic impairment may prevent proper drug metabolism.
5. Severe Kidney Disease (for high doses)
   • Patients on dialysis or with severe renal impairment may require dosage adjustments.
6. History of NAION (Non-Arteritic Anterior Ischemic Optic Neuropathy)
   • Increased risk of sudden vision loss.
7. Known Hypersensitivity or Allergy
   • History of allergic reaction to sildenafil, tadalafil, or any of their inactive ingredients.
8. Concomitant Use with Riociguat (Adempas)
   • Used for pulmonary hypertension, it can dangerously lower blood pressure when combined with PDE5 inhibitors.

Relative Contraindications (Use with Caution):

1. History of Stroke or Heart Attack (past 6–12 months)
   • May increase cardiovascular risk, especially in unstable patients.
2. Uncontrolled Hypertension (Very High Blood Pressure)
   • Can worsen cardiovascular strain.
3. Active Peptic Ulcers or Gastrointestinal Bleeding
   • May increase bleeding risk due to mild blood pressure effects.
4. Severe Retinitis Pigmentosa
   • Some forms of this genetic eye disease may be worsened by PDE5 inhibitors.
5. Use with Alpha-Blockers (e.g., tamsulosin, doxazosin)
   • Can cause severe hypotension (low blood pressure) when combined.
6. Bleeding Disorders
   • Can potentially increase the risk of bleeding due to mild platelet inhibition effects.

Key Differences in Contraindications:

Condition	Sildenafil	Tadalafil
Duration of Action	4–6 hours	Up to 36 hours (longer risk of interactions)
Food Interactions	High-fat meals may delay absorption	Less affected by food
Kidney Impairment	More dose adjustment needed	Less kidney-dependent metabolism
Liver Impairment	Avoid in severe cases	Avoid in severe cases, but may be better tolerated than sildenafil

Both drugs should only be used under medical supervision in patients with significant cardiovascular disease, kidney disease, or other risk factors.