Sildenafil (oral route) - Side effects & dosage — Uses, Dosage, Side Effects & Safety

Drug class: Phosphodiesterase type 5 (PDE5) inhibitor

At a glance: Sildenafil, a phosphodiesterase type 5 (PDE5) inhibitor, is primarily utilized for the treatment of various conditions, including erectile dysfunction and pulmonary arterial hypertension. Its mechanism involves increasing cyclic guanosine monophosphate (cGMP) levels, leading to smooth muscle relaxation and increased blood flow. Common side effects should be discussed with a healthcare provider. Patients should be monitored for cardiovascular status due to potential hemodynamic effects.

Overview

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Clinical information

[{"title":"Mechanism of Action","content":"Sildenafil selectively inhibits phosphodiesterase type 5 (PDE5), the enzyme responsible for degradation of cyclic guanosine monophosphate (cGMP) in the corpus cavernosum and pulmonary vasculature. Increased cGMP leads to smooth muscle relaxation, vasodilation, and enhanced blood flow to the penis and lungs. "},{"title":"Detailed Pharmacokinetics","content":"Absorption: Rapidly absorbed orally; peak plasma concentrations in 30–120 minutes. Bioavailability ~40%. Distribution: Volume of distribution ~105 L. Protein binding ~96%. Metabolism: Primarily hepatic via CYP3A4 (major) and CYP2C9 (minor). Elimination: Terminal half-life ~3–5 hours. Excreted mainly as metabolites in feces (80%) and urine (13%). "},{"title":"Clinical Contraindications & Precautions","content":"Contraindicated with concurrent nitrate or guanylate cyclase stimulator use, severe hypotension, recent stroke or myocardial infarction, severe hepatic impairment, hereditary degenerative retinal disorders (e.g., retinitis pigmentosa). Use caution in patients with anatomical penile deformation, bleeding disorders, peptic ulcer, or cardiovascular risk. "},{"title":"Dose Adjustments","content":"Renal: No adjustment for mild/moderate impairment; consider lower starting dose for severe impairment. Hepatic: Lower starting d

Therapeutic uses

• Erectile dysfunction
• Pulmonary arterial hypertension
• Pulmonary arterial hypertension (specific formulation and dosing)

Common side effects

• Headache
• Flushing
• Dyspepsia
• Nasal congestion
• Visual disturbances (e.g., blurred vision, cyanopsia)
• Dizziness
• Back pain

Drug interactions

• Strong CYP3A4 inhibitors (e.g., certain antifungals, some HIV protease inhibitors) increase sildenafil blood levels, requiring dose adjustment
• Grapefruit juice may increase drug levels
• Alpha-blockers can cause additive blood-pressure-lowering effects
• Contraindicated with nitrates in any form due to risk of severe, life-threatening hypotension

Contraindications

• Concurrent use with riociguat (a guanylate cyclase stimulator)
• Concurrent use of any organic nitrate, in any form or dose schedule

Precautions & warnings

Use with caution in patients with cardiovascular disease, as sexual activity carries a degree of cardiac risk. Rare reports of sudden vision or hearing loss have been associated with use; discontinue and seek medical attention if these occur. Priapism (erection lasting more than 4 hours) is a medical emergency.

Pregnancy

Not indicated for use in women; safety data in pregnancy for this indication are not applicable.

When to seek emergency help

Seek emergency care for an erection lasting longer than 4 hours, sudden vision loss, or sudden hearing loss.

Frequently Asked Questions about Sildenafil (oral route) - Side effects & dosage

How long does sildenafil take to work?

Sildenafil usually starts working within 30 to 60 minutes after taking it. Sexual stimulation is required for it to be effective.

Can I take sildenafil every day?

For erectile dysfunction, sildenafil is typically taken as needed, not more than once per day. For pulmonary arterial hypertension, it is taken regularly as prescribed.

Is it safe to use sildenafil with alcohol?

Drinking small amounts of alcohol is generally safe, but excessive alcohol can increase the risk of side effects such as low blood pressure, dizziness, or fainting.

What should I do if I experience vision changes?

Stop taking sildenafil and seek medical attention immediately if you notice sudden vision loss or changes in vision.

Can women use sildenafil?

Sildenafil is not approved for sexual dysfunction in women. It may be prescribed for pulmonary arterial hypertension in both men and women.

Are there any foods I should avoid while taking sildenafil?

Avoid grapefruit and grapefruit juice, as they can increase sildenafil levels and side effects.

What happens if I take sildenafil with nitrates?

Taking sildenafil with nitrates can cause a dangerous drop in blood pressure. This combination is strictly contraindicated.

Educational information only. Always consult a qualified healthcare professional before starting, stopping, or changing any medication.