PDE5 inhibitors
Sildenafil, tadalafil and vardenafil. They don’t create desire; they help blood flow do its job when you’re aroused. Also used for prostate symptoms and high blood pressure in the lungs.
Quick answer: PDE5 inhibitors (sildenafil, tadalafil, vardenafil) treat erectile dysfunction by improving blood flow when you’re sexually aroused. They work for about 2 in 3 men. Tadalafil lasts up to 36 hours and, at 5 mg daily, also eases prostate urine symptoms. Common side effects are headache, flushing, a blocked nose and indigestion. Never take them with nitrates (angina sprays or tablets) or amyl nitrite (“poppers”).
At a glance
- For
- Erectile dysfunction; prostate urine symptoms (daily tadalafil); pulmonary arterial hypertension (specialist)
- Works
- Firmer erections for about 2 in 3 men; less after prostate surgery or with severe diabetes
- Cost
- Not on the PBS for erectile dysfunction (except some veterans): a private script; generics are much cheaper than the brands
- Kicks in
- 30–60 minutes; arousal is still needed
- Dose
- As needed before sex, or tadalafil 5 mg daily; lower doses with some medicines and kidney or liver disease
- Watch for
- Headache, flushing, blocked nose, indigestion, back pain, dizziness
Plumbing, not mood. It needs arousal to work, and it’s a check-up prompt: erection problems can be an early sign of heart disease.
Brand names
- Sildenafil: Viagra and many generics
- Tadalafil: Cialis and many generics
- Vardenafil: Levitra and generics
How it works
An erection happens when nitric oxide relaxes the blood vessels in the penis so blood flows in. PDE5 is the enzyme that switches that signal off. Blocking it keeps the signal on for longer, but only once arousal has started it.
Used for
- Erectile dysfunction (TGA-approved)
- Prostate enlargement urine symptoms: tadalafil 5 mg daily (TGA-approved)
- Pulmonary arterial hypertension: specific brands and doses, specialist-prescribed
- Off label: Raynaud’s phenomenon, altitude sickness prevention in some people, sexual side effects of antidepressants
Compared
- Fast, shortSildenafil (Viagra and generics)
- Starts
- 30–60 minutes; slower after a fatty meal
- Lasts
- About 4–5 hours
- Doses
- 25–100 mg, about an hour before sex
- Quirk
- Blue-tinged or blurred vision in some
- Long-actingTadalafil (Cialis and generics)
- Starts
- 30 minutes to 2 hours; food doesn’t matter
- Lasts
- Up to 36 hours (“the weekend pill”)
- Doses
- 10–20 mg as needed, or 5 mg every day
- Quirk
- Back and muscle aches; 5 mg daily also eases prostate urine symptoms
- Fast, shortVardenafil (Levitra and generics)
- Starts
- 25–60 minutes
- Lasts
- About 4–5 hours
- Doses
- 5–20 mg
- Quirk
- Avoid with some heart rhythm medicines
Side effects
Headache and flushing are the most common, followed by a blocked nose, indigestion and dizziness. Tadalafil more often causes back and muscle aches; sildenafil can tint vision blue. Serious effects are rare.
Full side-effect list (from the product information)
How often, from the official product information. Bold = serious.
Very common more than 1 in 10
- Headache
Common 1 in 10 to 1 in 100
- Flushing
- Blocked or runny nose
- Indigestion or reflux
- Dizziness
- Back or muscle aches (tadalafil)
- Vision changes: blue tinge, blur, light sensitivity (sildenafil)
Uncommon 1 in 100 to 1 in 1,000
- Palpitations or fast heartbeat
- Low blood pressure or fainting
- Nosebleeds
- Eye pain or red eyes
- Painful erections
Rare 1 in 1,000 to 1 in 10,000
- Priapism (erection over 4 hours)
- Sudden vision loss (NAION)
- Sudden hearing loss
- Heart attack, stroke or heart rhythm problems (mostly in people with heart disease)
- Severe allergic reactions
Get help urgently if
- An erection lasting more than 4 hours: go to an emergency department
- Sudden loss of vision or hearing
- Chest pain during or after sex: stop, don’t take a nitrate, call 000 and tell them you took a PDE5 inhibitor
- Fainting
Good to know
- Never with nitrates (glyceryl trinitrate spray or tablets, isosorbide) or “poppers”: blood pressure can crash. Not with riociguat.
- Alpha blockers (e.g. tamsulosin, prazosin): start low and space doses; dizziness is more likely.
- Grapefruit and some antibiotics, antifungals and HIV medicines raise levels.
- Avoid heavy alcohol; it worsens dizziness and erections.
- Get checked: erection problems can be an early sign of heart disease, diabetes or low testosterone. Buy only from an Australian pharmacy: online fakes are common.
Common questions
Do PDE5 inhibitors work without arousal?
No. They help blood flow once you’re sexually aroused, but they don’t create desire or an erection on their own.
What’s the difference between sildenafil and tadalafil?
Sildenafil works for about 4–5 hours and is slowed by fatty food. Tadalafil lasts up to 36 hours, isn’t affected by food, and can be taken as 5 mg daily, which also helps prostate urine symptoms.
Why can’t you take Viagra with nitrates?
Both lower blood pressure, and together they can cause a dangerous drop. That includes angina sprays and tablets and amyl nitrite (“poppers”).
Information only. Not a recommendation or endorsement of any product. Whether a medicine suits you depends on your health and other medicines, so talk to your doctor or pharmacist. In an emergency, call 000 (Australia) or your local emergency number. From a mobile, 112 works in most countries.
More information
- Viagra product information (TGA)
- Cialis product information (TGA)
- Healthy Male: Erectile dysfunction
- Healthdirect: Medicines information
maladywise.com/medicines/pde5-inhibitors/