If lifestyle changes and supplements haven’t resolved your erectile dysfunction, ED medications are the logical next step — and they work for roughly 70% of men. But Viagra, Cialis, Levitra, and Stendra are not interchangeable. They differ in how fast they act, how long they last, how they interact with food and alcohol, and how much they cost.
This guide compares the four FDA-approved ED medications so you can have an informed conversation with your doctor about which one fits your situation. (This is educational content, not medical advice — all of these drugs require a prescription and a doctor’s evaluation.)
How ED Medications Work
All four major ED medications belong to the same drug class: PDE5 inhibitors (phosphodiesterase type 5 inhibitors). During arousal, your body releases nitric oxide, which relaxes the smooth muscle in the penis and lets blood flow in. An enzyme called PDE5 reverses that process. PDE5 inhibitors block the enzyme, making it easier to achieve and maintain an erection — but only when you’re sexually stimulated. They do not create arousal on their own, and they don’t fix the underlying cause of ED.
That last point matters: ED is often an early warning sign of cardiovascular disease. ED medications treat the symptom, so getting a proper workup is just as important as getting a prescription.
Viagra (Sildenafil): The Original
- Onset: 30–60 minutes
- Duration: 4–5 hours
- Food interaction: High-fat meals delay absorption significantly
- Typical dose: 50 mg (range 25–100 mg)
Sildenafil has the longest track record — approved in 1998 and studied in thousands of clinical trials. It’s effective for about 70% of men and now costs very little as a generic. The main practical drawback: timing. You need to take it on a relatively empty stomach, roughly an hour before sex, and the window closes after 4–5 hours.
Cialis (Tadalafil): The Long-Acting Option
- Onset: 30–45 minutes
- Duration: up to 36 hours (“the weekend pill”)
- Food interaction: None significant
- Typical dose: 10 mg as needed, or 2.5–5 mg daily
Tadalafil’s 36-hour window removes the pressure of scheduling sex around a pill, which is why many men — and most urologists — favor it. It’s also the only ED medication approved as a low-dose daily tablet, an approach that restores spontaneity entirely. Bonus: daily tadalafil is also FDA-approved to treat BPH urinary symptoms, making it a two-for-one option for men over 50 dealing with both issues.
Levitra (Vardenafil): The Middle Ground
- Onset: 30–60 minutes
- Duration: 4–5 hours
- Food interaction: High-fat meals delay absorption
- Typical dose: 10 mg (range 5–20 mg)
Vardenafil is pharmacologically similar to sildenafil but slightly more potent at the molecular level, which matters for some men with diabetes-related ED. Brand-name Levitra has been discontinued in the U.S., but generic vardenafil remains available.
Stendra (Avanafil): The Fast One
- Onset: as fast as 15 minutes
- Duration: 6+ hours
- Food interaction: Minimal
- Typical dose: 100 mg (range 50–200 mg)
Avanafil is the newest PDE5 inhibitor (2012) and the most selective, which translates to faster onset and fewer visual side effects. The trade-off is cost — generic options are newer and pricier than sildenafil or tadalafil.
ED Medications Compared: Quick Table
| Drug | Onset | Duration | Food effect | Generic cost |
|---|---|---|---|---|
| Viagra (sildenafil) | 30–60 min | 4–5 h | Yes, significant | $ |
| Cialis (tadalafil) | 30–45 min | 24–36 h | No | $ |
| Levitra (vardenafil) | 30–60 min | 4–5 h | Yes | $$ |
| Stendra (avanafil) | 15–30 min | 6+ h | Minimal | $$$ |
Side Effects and Safety: What to Know Before Taking ED Medications
Common side effects across all PDE5 inhibitors include headache, flushing, nasal congestion, indigestion, and back pain (more common with tadalafil). Most are mild and fade as the drug clears.
The critical safety rule: never combine ED medications with nitrates (nitroglycerin, isosorbide) — the combination can cause a life-threatening drop in blood pressure. Caution also applies to alpha-blockers (commonly prescribed for BPH), certain antifungals and antibiotics, and heavy alcohol use. Men with recent heart attack or stroke, severe liver disease, or uncontrolled blood pressure need a cardiology green light first.
Seek immediate medical care for an erection lasting more than 4 hours (priapism) or sudden vision or hearing loss — rare but serious.
Which of the ED Medications Is Right for You?
- You want the cheapest proven option: generic sildenafil.
- You want spontaneity or also have BPH: tadalafil (daily or as needed).
- You want the fastest onset: avanafil.
- Diabetes-related ED that didn’t respond to sildenafil: ask about vardenafil.
If performance anxiety is part of the picture, medication often works best combined with addressing the psychological side of ED. And because PDE5 inhibitors don’t cure anything, pairing them with the lifestyle strategies that can reverse erectile dysfunction naturally gives you the best long-term outcome.
What About Supplements Instead of ED Medications?
Supplements like L-citrulline and Panax ginseng have modest evidence but are far weaker than prescription options — we break down the data in our guide to the best ED supplements. They may help mild cases; they are not substitutes for moderate to severe ED. Also avoid “herbal Viagra” products sold online — the FDA regularly finds them adulterated with unlabeled sildenafil at unpredictable doses.
When ED Medications Don’t Work
About 30% of men don’t respond to the first PDE5 inhibitor they try. Before concluding they failed: confirm you took the full dose correctly (empty stomach for sildenafil, adequate stimulation, 6–8 attempts). If they still fail, options include switching drugs, daily tadalafil, vacuum erection devices, intracavernosal injections (alprostadil), and — for refractory cases — penile implants, which have satisfaction rates above 90%. Non-response is also a strong signal to check testosterone: low testosterone reduces PDE5 inhibitor effectiveness.
Frequently Asked Questions
Can I buy ED medications without a prescription?
No — all PDE5 inhibitors require a prescription in the U.S. Telehealth platforms have made the process fast and discreet, but a legitimate provider will always review your health history first.
Are generic ED medications as good as brand name?
Yes. Generics must demonstrate bioequivalence to the FDA. Generic sildenafil and tadalafil contain the same active molecules as Viagra and Cialis at a fraction of the price.
Do ED medications increase testosterone?
No. They act on blood flow, not hormones. If fatigue, low libido, and poor erections cluster together, get your testosterone levels checked.