Pharmacology · Topic 30 of 110
PDE-5 Inhibitors (Sildenafil, Tadalafil)
Start here
Tap any line to see why it matters
PDE-5 Inhibitors (Sildenafil, Tadalafil)
(Sildenafil, tadalafil, vardenafil) Treat erectile dysfunction by relaxing smooth muscle. The danger is severe hypotension with any nitrate.
Used for · don't give
Used for
Don't give
Also contraindicated with riociguat (a pulmonary hypertension drug) — the same additive hypotension. Sildenafil (Revatio) and tadalafil (Adcirca) also treat pulmonary arterial hypertension; a client on one never adds an erectile dysfunction PDE-5 product.
How it works
Blocks cGMP breakdown — smooth muscle relaxes and blood flows into the penis
Side effects
Mild effects are common; sudden vision or hearing loss is not
Assess & monitor
Alpha-1 blockers: tamsulosin, doxazosin (additive hypotension). CYP3A4 inhibitors: ritonavir, ketoconazole, itraconazole, erythromycin.
Red flags
Giving it
Ask about nitrates both ways — before the PDE-5, and before any nitroglycerin
About 1 hour before sex (30 minutes to 4 hours), no more than once a day — a high-fat meal delays it.
Works up to 36 hours; can be once daily regardless of food or timing — daily dosing also treats BPH.
Stable on the alpha-1 blocker first, then the lowest PDE-5 dose — additive hypotension.
Ritonavir, ketoconazole, itraconazole, erythromycin and grapefruit raise levels — expect a lower dose.
More detail
Nursing priorities
Sildenafil or tadalafil?
| Sildenafil | Tadalafil | |
|---|---|---|
| Timing | About 1 hour before sex; max once a day | Up to 36 hours; can be once daily |
| Food | A high-fat meal delays onset | Regardless of food |
| No nitrate within | 24 hours (same for vardenafil) | 48 hours |
| Typical effect | Bluish tinge to vision | Back pain, muscle aches |
| Also treats | Pulmonary arterial hypertension (Revatio) | BPH (daily); pulmonary arterial hypertension (Adcirca) |
Teach your patient
Before any nitroglycerin, ask about erectile dysfunction drugs — sildenafil or vardenafil in 24 hours, tadalafil in 48: no nitrate.
Sources · Viagra (sildenafil) label (DailyMed) · Cialis (tadalafil) label (DailyMed) · Levitra (vardenafil) label (DailyMed) · Sildenafil (MedlinePlus) · Nitroglycerin Use in the Emergency Department (Open Access Emerg Med, PMC) · Separation for nitrates and PDE-5 inhibitors (meded101) · Follow your facility's protocol for nitrate administration.
PDE-5 Inhibitors (Sildenafil, Tadalafil)
PDE-5 inhibitors are drugs such as sildenafil, tadalafil and vardenafil that treat erectile dysfunction by blocking cGMP breakdown so smooth muscle relaxes and blood flows into the penis, working only with sexual stimulation. Their most important safety rule is that they are never combined with a nitrate in any form, including nitroglycerin, isosorbide or amyl nitrite poppers, because the combination can cause severe, possibly fatal hypotension. Before giving nitroglycerin for chest pain, the nurse asks about these drugs: no nitrate within 24 hours of sildenafil or vardenafil, or 48 hours of tadalafil. A client on an alpha-1 blocker starts at the lowest dose once stable. Clients are taught that an erection lasting more than 4 hours is an emergency, and that sudden vision or hearing loss means stopping the drug and seeking care immediately. Headache, flushing, nasal congestion and indigestion are common and usually mild. Sildenafil is taken about an hour before sex, while tadalafil lasts up to 36 hours and, taken daily, also treats BPH symptoms.
Loading questions…
Go further
- Guide94 Million Alaris IV Sets Recalled. The Trouble Zone: Under 1 mL/hFDA's October update says some BD Alaris sets perform worse than BD disclosed, mostly at low rates and small boluses. What's new and what to do.
- GuideExplain It Simply: The Three-Sentence Fix for a Missed Nursing QuestionWhen you missed a question because of one fact, you need the fact, why it decides the question, and the trap. How NurseSavvy’s Explain simply mode does it in 50 words, with a real example.
- FinderAI Prompt Library for Nursing StudentsEvery copy-ready AI prompt from our nursing study guides in one place: concept explanations, rationale autopsies, pharmacology, ABGs, and care plans.
Ready to practice this topic?
Get a personalized study plan built around this topic — free to try, no card needed.