The most effective medicines for erectile dysfunction (ED) are a class of oral drugs called PDE5 inhibitors, which include sildenafil (Viagra), tadalafil (Cialis), vardenafil (Levitra), and avanafil (Stendra). All four work through the same basic mechanism and have similar success rates, so the “best” one depends on how you want it to fit into your life: how quickly you need it to work, how long you want the effect to last, and how often you have sex.
How ED Medications Work
During arousal, your body releases a chemical that relaxes the smooth muscle in the blood vessels of the penis, allowing blood to flow in and produce an erection. An enzyme in your body naturally breaks down that chemical. PDE5 inhibitors block that enzyme, so the chemical stays active longer and blood flow increases. The key point: these drugs don’t create arousal on their own. You still need sexual stimulation for them to work.
Comparing the Four Main Options
All four PDE5 inhibitors are effective, but they differ in timing and flexibility.
Sildenafil (Viagra) is the oldest and most studied. It can start working in as little as 11 minutes for some men, though most should plan to take it 30 to 60 minutes before sex. Its effects last roughly 4 to 6 hours. One significant drawback: eating a high-fat meal around the time you take it delays absorption by about an hour and reduces the peak concentration of the drug in your blood by nearly 30%. That means a big dinner before a date night can blunt its effectiveness.
Tadalafil (Cialis) stands out because of its long half-life, approximately 17.5 hours in healthy men and even longer in older adults. That extended window means a single dose can remain active for up to 36 hours, earning it the nickname “the weekend pill.” Onset is similar to the others, around 14 minutes at the earliest, but the practical advantage is that you don’t have to time sex around the pill as precisely. Tadalafil is also the only one available in a low daily dose, which provides a continuous baseline so you can be ready without planning ahead.
Vardenafil (Levitra) has a profile similar to sildenafil, with onset around 14 minutes and a duration of about 4 to 6 hours. Like sildenafil, fatty foods can interfere with absorption.
Avanafil (Stendra) is the newest of the four. It was designed to act faster and with fewer side effects. Some men find it effective in as little as 15 minutes. It also tends to be more selective in how it works, which can mean fewer issues with flushing and headaches.
Worth noting: even when studies detect a response as early as 11 to 14 minutes, fewer than 40% of men actually experience success that quickly. Planning for at least 30 minutes is more realistic for most people.
Daily Tadalafil vs. On-Demand Dosing
Tadalafil gives you a choice no other ED drug offers. You can take a higher dose before sex (on-demand), or you can take a small dose every day regardless of whether you plan to have sex that night. A meta-analysis comparing the two approaches found that daily dosing produced slightly better scores on standardized measures of erectile function, particularly after 24 weeks of use. The daily group also reported higher rates of successful penetration and maintained erections.
From a side-effect standpoint, on-demand dosing had a somewhat higher rate of side effects overall, likely because each individual dose is larger. Common side effects for both approaches include headache, indigestion, back pain, and nasal congestion, with no significant difference between the two for any specific complaint. Daily dosing tends to appeal to men who have sex more than twice a week or who prefer spontaneity over planning. On-demand dosing makes more sense if your sexual activity is less frequent and you’d rather not take a pill every day.
What to Do if Pills Don’t Work
Oral medications work for a large majority of men with ED, but not everyone responds. If you’ve tried more than one PDE5 inhibitor at full dose and still aren’t getting results, the next step is usually a penile injection. This involves using a very fine needle to inject a medication directly into the side of the penis before sex. The drug works by relaxing blood vessel walls and increasing blood flow through a different chemical pathway than oral pills use. Most men find the injection far less painful than they expect, and the erection typically develops within 5 to 15 minutes.
Other options beyond injections include a small pellet inserted into the urethra, vacuum erection devices (a plastic cylinder that uses suction to draw blood into the penis), and, as a last resort, surgically implanted penile prostheses. Each option has trade-offs in convenience, cost, and how natural the result feels, so the right choice depends on your specific situation and what matters most to you.
A Newer Form of Sildenafil
In early 2026, the FDA approved a sildenafil oral film, a thin dissolvable strip you place on your tongue. It doesn’t require water or swallowing a tablet, making it more discreet. A phase 3 trial of 475 men showed it was significantly more effective than placebo over 12 weeks. Peak blood levels are reached in a median of about 80 minutes, and like traditional sildenafil tablets, it can be taken 30 minutes to 4 hours before activity. This is the same active ingredient as Viagra, just in a different delivery format.
Who Should Not Take ED Medications
PDE5 inhibitors are safe for most men, but there is one critical exception: nitrate medications. If you take nitroglycerin patches, sublingual nitroglycerin tablets, isosorbide, or any other nitrate-based drug for chest pain or heart disease, combining them with an ED pill can cause a sudden, dangerous drop in blood pressure. Research from the American Heart Association showed that the combination produces “large and protracted decreases in systemic blood pressure and coronary blood flow,” particularly in men whose arteries are already partially blocked. In severe cases, the drop in coronary blood flow triggers a cycle of worsening cardiac ischemia that can be fatal.
This isn’t a theoretical risk. It applies to all PDE5 inhibitors, not just sildenafil. If you use recreational drugs containing nitrates (often called “poppers”), the same danger applies. Men on nitrates have other ED treatment options available, but oral PDE5 inhibitors are firmly off the table.
Why “Natural” ED Supplements Are Risky
Walk through any gas station or browse online and you’ll find dozens of supplements marketed as natural ED treatments. The FDA has issued hundreds of warnings about these products. Many are contaminated with undeclared pharmaceutical ingredients, often the same active compounds found in prescription ED drugs, but at unpredictable doses and without any of the safety labeling. That means you could unknowingly be taking a PDE5 inhibitor while also on nitrates or another conflicting medication. These products are classified by the FDA as a type of medication health fraud.
If a supplement seems to work suspiciously well for erections, there’s a good chance it contains a hidden drug. Sticking with a prescription from a licensed provider is far safer, and often cheaper than the premium-priced supplements claiming to be all-natural.
Tips to Get the Most From Your Medication
If you’re taking sildenafil or vardenafil, avoid heavy or high-fat meals close to when you take your dose. A greasy dinner can delay absorption by a full hour and reduce how much of the drug actually reaches your bloodstream. Tadalafil is less affected by food, which is another reason some men prefer it.
Alcohol in moderate amounts is generally fine, but heavy drinking impairs erections on its own and can amplify side effects like dizziness and low blood pressure. Timing also matters: taking the pill well before you need it, rather than rushing at the last minute, gives it the best chance to reach effective levels. And if one medication doesn’t work after several attempts at the right dose, trying a different PDE5 inhibitor is reasonable. Men who don’t respond well to one sometimes do better with another, even though the drugs share a mechanism.