Sildenafil

PDE5 Inhibitor·Urology

Erectile dysfunction (ED), Pulmonary Arterial Hypertension (PAH)

Authority requiredPBSPDE5 INHIBITORViagra, Revatio (PAH)25 mg tablet+2

Max Dose

100 mg/day

Half-life

4 h

Nitrates

FATAL

Blue Vision

RISK

Rapid Summary

Overview

Potent Phosphodiesterase-5 (PDE5) inhibitor. Enhances nitric oxide-mediated vasodilation in the corpus cavernosum and pulmonary vasculature.

Maximum Dose

Max 100 mg/day (Erectile Dysfunction).

Clinical Focus

Absolutely contraindicated within 24 hours of ANY nitrate administration due to risk of refractory, fatal hypotension.

Bottom Line

Sildenafil is the original PDE5 inhibitor for erectile dysfunction and pulmonary hypertension, but is absolutely contraindicated with nitrates due to fatal hypotension risk.

Formulation & Access

Brand Names

Viagra, Revatio (PAH)

Oral Routes

Tablets (25 mg, 50 mg, 100 mg).

Parenteral

Ampoules for IV use (ICU for PAH only).

Prescribing & PBS

Private script (ED). Authority Required PBS for PAH.

Indications & Use

Primary

PBSTGA

Erectile dysfunction (ED), Pulmonary Arterial Hypertension (PAH).

Off-Label

OFF

Raynaud's phenomenon.

Clinical Place

First-line oral therapy for ED. Essential vasodilator in PAH.

Quick reference

Class & Role

PDE5 Inhibitor — Potent Phosphodiesterase-5 (PDE5) inhibitor.

Route / Formulation

Tablets (25 mg, 50 mg, 100 mg). (Viagra, Revatio (PAH))

Usual Dose & Max

PO 50 mg approximately 1 hour before sexual activity. Max 100 mg/day.

Key Indication Doses

Erectile Dysfunction: PO 50 mg approximately 1 hour before sexual activity. Max 100 mg/day. Pulmonary Arterial HTN: PO 20 mg TDS (Requires specialist initiation). Elderly / Renal / Hepatic: Start at 25 mg if eGFR < 30, severe hepatic impairment, or age > 65.

Best Uses

Sildenafil is the original PDE5 inhibitor for erectile dysfunction and pulmonary hypertension, but is absolutely contraindicated with nitrates due to fatal hypotension risk.

Avoid / Cautions

Concurrent use of ANY nitrates (GTN, isosorbide). High cardiovascular risk preventing sexual activity. Recent MI/Stroke.

Key Risks

Cardiovascular: Severe hypotension (if interacting). MODERATE — Flushing, headache, nasal congestion. Ocular: Cyanopsia (blue-tinted vision). RARE — NAION (sudden permanent blindness). Genitourinary: Priapism (erection > 4 hours, medical emergency requiring aspiration/phenylephrine).

Key Interactions

Nitrates (GTN patch, spray, sublingual). Fatal hypotension. Must wait 24 hours after Sildenafil before giving a nitrate. Alpha-blockers (Prazosin, Tamsulosin). Space doses by at least 4 hours to prevent orthostatic collapse. CYP3A4 inhibitors (Clarithromycin, Grapefruit juice) drastically increase Sildenafil levels. Max dose 25mg.

Monitoring

Warn patients to seek immediate ED care for chest pain, sudden vision loss, or erection > 4 hours. No specific routine laboratory tests required.

Clinical Pearl

If a male patient presents to ED with crushing chest pain, you MUST ask if they have taken Viagra/Cialis before you administer GTN. Giving GTN will kill them if the PDE5i is still in their system.

Access

Authority requiredViagra, Revatio (PAH)25 mg tablet

Brand: Viagra, Revatio (PAH)
PBS status: Authority required
Formulation: Tablets (25 mg, 50 mg, 100 mg)

Sildenafil

PDE5 Inhibitor·Urology

Erectile dysfunction (ED), Pulmonary Arterial Hypertension (PAH)

Authority requiredPBSPDE5 INHIBITORViagra, Revatio (PAH)25 mg tablet+2

Max Dose

100 mg/day

Half-life

4 h

Nitrates

FATAL

Blue Vision

RISK

Rapid Summary

Overview

Potent Phosphodiesterase-5 (PDE5) inhibitor. Enhances nitric oxide-mediated vasodilation in the corpus cavernosum and pulmonary vasculature.

Maximum Dose

Max 100 mg/day (Erectile Dysfunction).

Clinical Focus

Absolutely contraindicated within 24 hours of ANY nitrate administration due to risk of refractory, fatal hypotension.

Bottom Line

Sildenafil is the original PDE5 inhibitor for erectile dysfunction and pulmonary hypertension, but is absolutely contraindicated with nitrates due to fatal hypotension risk.

Formulation & Access

Brand Names

Viagra, Revatio (PAH)

Oral Routes

Tablets (25 mg, 50 mg, 100 mg).

Parenteral

Ampoules for IV use (ICU for PAH only).

Prescribing & PBS

Private script (ED). Authority Required PBS for PAH.

Indications & Use

Primary

PBSTGA

Erectile dysfunction (ED), Pulmonary Arterial Hypertension (PAH).

Off-Label

OFF

Raynaud's phenomenon.

Clinical Place

First-line oral therapy for ED. Essential vasodilator in PAH.

Quick reference

Class & Role

PDE5 Inhibitor — Potent Phosphodiesterase-5 (PDE5) inhibitor.

Route / Formulation

Tablets (25 mg, 50 mg, 100 mg). (Viagra, Revatio (PAH))

Usual Dose & Max

PO 50 mg approximately 1 hour before sexual activity. Max 100 mg/day.

Key Indication Doses

Best Uses

Sildenafil is the original PDE5 inhibitor for erectile dysfunction and pulmonary hypertension, but is absolutely contraindicated with nitrates due to fatal hypotension risk.

Avoid / Cautions

Concurrent use of ANY nitrates (GTN, isosorbide). High cardiovascular risk preventing sexual activity. Recent MI/Stroke.

Key Risks

Key Interactions

Monitoring

Warn patients to seek immediate ED care for chest pain, sudden vision loss, or erection > 4 hours. No specific routine laboratory tests required.

Clinical Pearl

If a male patient presents to ED with crushing chest pain, you MUST ask if they have taken Viagra/Cialis before you administer GTN. Giving GTN will kill them if the PDE5i is still in their system.

Access

Authority requiredViagra, Revatio (PAH)25 mg tablet

Brand: Viagra, Revatio (PAH)
PBS status: Authority required
Formulation: Tablets (25 mg, 50 mg, 100 mg)