This inhibition increases levels of cyclic guanosine monophosphate (cGMP).

Elevated cGMP causes relaxation of smooth muscle and vasodilation in penile tissue → increased blood flow → erection (when sexual stimulation is present)

• This inhibition increases levels of cyclic guanosine monophosphate (cGMP).
• Elevated cGMP causes relaxation of smooth muscle and vasodilation in penile tissue → increased blood flow → erection (when sexual stimulation is present)

Contraindications:

• Concomitant nitrate therapy (e.g., nitroglycerin) → risk of life-threatening hypotension

• Riociguat (guanylate cyclase stimulator)

• Known hypersensitivity to sildenafil or its components

• Severe hypotension (BP < 90/50 mmHg)

• Recent myocardial infarction or stroke (within last 6 months)

• Severe hepatic impairment

Precautions:

• Use caution in patients with:

  • Cardiovascular disease

  • Retinitis pigmentosa (risk of visual loss)

  • Peptic ulcer disease

  • Bleeding disorders

  • Alpha-blocker therapy (orthostatic hypotension risk)

• Avoid combining with recreational nitrates (e.g., poppers)

• Should not be used more than once daily

Major Drug Interactions:

• Nitrates: Severe hypotension risk → absolute contraindication
• Alpha-blockers: Additive hypotension → dose timing should be staggered
• CYP3A4 inhibitors (e.g., ketoconazole, erythromycin, ritonavir):
• ↑ sildenafil concentration → increase side effects
• CYP3A4 inducers (e.g., rifampin, carbamazepine):
• ↓ sildenafil levels → reduced efficacy
• Alcohol: May enhance hypotensive effects and dizziness
• Other interactions:
• Antihypertensive medications: Caution due to additive BP-lowering effects

Common Side Effects:

• Headache
• Flushing (facial redness)
• Nasal congestion
• Dyspepsia (indigestion)
• Visual disturbances (blue-tinted vision, blurred vision)
• Dizziness or light-headedness

Less Common but Serious Side Effects:

• Priapism (erection lasting >4 hours) → medical emergency
• Sudden hearing loss
• Hypotension, especially with nitrates or alpha-blockers

Cardiovascular events in at-risk individuals (e.g., MI, arrhythmia)

Pregnancy (Category B – ED use not indicated):

• Animal studies: No teratogenic effects

• Human data: Limited for ED use; not recommended unless prescribed for PAH

• Off-label use during pregnancy (e.g., for uteroplacental insufficiency) is still under research

Breastfeeding:

• Unknown whether sildenafil is excreted in human milk

• Due to lack of data and potential systemic vasodilatory effects, it is not recommended while breastfeeding unless specifically prescribed by a physician

Store this medication at 68°F to 77°F (20°C to 25°C) and away from heat, moisture and light. Keep all medicine out of the reach of children. Throw away any unused medicine after the beyond use date. Do not flush unused medications or pour down a sink or drain

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