ED medication comparison: four PDE5 inhibitors

Sildenafil, tadalafil, vardenafil, and avanafil work on the same enzyme. They differ in how fast they start, how long a dose may help, how food changes absorption, and what else is on the label. Use the filters to narrow the table. The rows stay in the page for search engines even before JavaScript runs.

Medicine	Onset	Useful window	Food	Usual adult doses on the label	Cost pattern	Distinct label point
Sildenafil Viagra	Median peak about 60 minutes when fasting. May be taken from 30 minutes to 4 hours before activity.	Effect measured out to about 4 hours, weaker than at 2 hours.	High-fat meal: mean peak delayed about 60 minutes and about 29% lower.	25 mg, 50 mg, 100 mg. For most patients the label starts at 50 mg, no more than once a day.	FDA-approved generics are widely dispensed and usually cost much less than the brand. Confirm a same-day cash quote.	After a dose, labeling says it is unknown when a nitrate could be given safely.
Tadalafil Cialis	Often discussed as 30 minutes or longer. Full effect may take up to 2 hours.	Erectile function improved versus placebo for up to 36 hours. Not a 36-hour erection.	Label: take without regard to food.	As needed: start 10 mg; may move to 20 mg or 5 mg. Once daily: start 2.5 mg, may increase to 5 mg. Do not combine the patterns.	FDA-approved generic tablets are common for both patterns. Daily and as-needed tablets are different regimens.	In a life-threatening emergency, nitrate use is considered only after at least 48 hours, with monitoring.
Vardenafil Levitra, Staxyn	Levitra is taken about 60 minutes before activity.	A shorter window, in the same range as sildenafil, about 4–5 hours in clinical descriptions.	Levitra may be taken with or without food. Staxyn is placed on the tongue without liquid.	Levitra: start 10 mg; 5–20 mg. Also a 2.5 mg tablet. Staxyn: 10 mg orally disintegrating, not a milligram swap for Levitra.	Generics exist. Availability is less consistent than sildenafil at some pharmacies.	A safe nitrate interval has not been determined. Avoid in congenital long QT and with class Ia or III antiarrhythmics.
Avanafil Stendra	Starting dose 100 mg as early as about 15 minutes before activity. The 50 mg dose is timed at about 30 minutes.	About 6 hours in product descriptions. Still requires sexual stimulation.	May be taken with or without food.	50 mg, 100 mg, 200 mg. No more than once a day. Not used with strong CYP3A4 inhibitors.	Generic competition has been more limited than for sildenafil or tadalafil, so cash prices are often higher.	If a nitrate is judged necessary in a life-threatening emergency, the label says to wait at least 12 hours and monitor.

Scroll horizontally on a narrow screen. Duration is a treatment window, not the length of an erection.

How to read the differences

All four drugs inhibit phosphodiesterase type 5. During sexual stimulation, nerve signals in the penis release nitric oxide, which raises cyclic GMP and relaxes smooth muscle so blood can fill the corpora cavernosa. PDE5 breaks cyclic GMP down. Blocking PDE5 lets that signal last longer. Without stimulation, the signal is not started, so these tablets do not produce an automatic erection and they do not increase desire.

Choosing among them is mostly about schedule and other medicines. Someone who can plan intimacy and wants the lowest typical generic price often discusses sildenafil. Someone who wants a dose to cover a weekend, or who has urinary symptoms from an enlarged prostate that tadalafil is also labeled to treat, discusses tadalafil. Someone who wants the shortest labeled lead time discusses avanafil. Vardenafil is an alternative short-acting option, with extra caution if the QT interval is already a problem.

What the table leaves out

Price cells are patterns, not quotes. A useful comparison is the same generic name, the same strength, and the same quantity at two licensed pharmacies on the same day. Brand Viagra against generic sildenafil is a fair comparison of the same active ingredient. A 20 mg pulmonary-hypertension sildenafil tablet is a different labeled product. Do not assemble an ED dose from it unless the prescriber wrote it that way.

The table also leaves out treatments that are not PDE5 inhibitors: vacuum devices, alprostadil, and penile prostheses. Those are clinician-directed options when pills fail, are contraindicated, or are a poor fit. Lifestyle measures and alternatives covers them.

Interactions that apply to every row

Organic nitrates in any form, including poppers, are contraindicated. Read nitrates and cardiac risk.
Riociguat and vericiguat are contraindicated.
Alpha-blockers and other blood-pressure medicines can add to dizziness. The labels tell prescribers to start low and only after the alpha-blocker dose is stable.
Strong CYP3A4 inhibitors raise levels. Avanafil’s label says not to use it with them at all.
Do not stack two PDE5 inhibitors, and do not add a gas-station “enhancement” pill. Many of those products already contain a hidden PDE5 inhibitor.

Sources: U.S. prescribing information for sildenafil tablets, tadalafil tablets, Levitra (vardenafil), and Stendra (avanafil), via FDA and DailyMed. Individual generic labels can differ in inactive ingredients and imprint. Read the leaflet in the box you were dispensed.