ED Medication Selector: Sildenafil vs Tadalafil vs Vardenafil
Answer 10 quick questions to screen for unsafe combinations and see which ED tablet best matches how you want to use it – ready to discuss with your prescriber.
Medically reviewed by John Creek [M.B.B.S] · Updated 8 Oct 2026Start the selector ↓
Which ED tablet fits you?
Step 1 checks safety. Step 2 matches the options to how you want to use them.
This tool summarises FDA label information to support a conversation with a prescriber. It does not diagnose ED or decide whether a medicine is safe for you. ED can be an early sign of heart disease, so a check-up is recommended.
How the ED medication selector works
The selector has two parts. First, a safety screen checks for combinations that are never safe with ED tablets, such as nitrates and riociguat, and flags situations where your prescriber needs to adjust the dose. Second, it scores sildenafil, on-demand tadalafil, daily tadalafil and vardenafil against your answers about timing, spontaneity, meals and urinary symptoms, using information from each medicine’s FDA label. The closest match appears first, with two alternatives.
Sildenafil vs tadalafil vs vardenafil compared
| Sildenafil | Tadalafil | Vardenafil | |
|---|---|---|---|
| Original brand | Viagra | Cialis | Levitra |
| Generics on MyRxBox | Cenforce, Fildena, Kamagra, Caverta, Penegra | Vidalista, Tadaflo, Megalis, Tazzle, Tadact | Vilitra, Valif |
| Label strengths | 25, 50, 100 mg | 2.5, 5, 10, 20 mg | 5, 10, 20 mg |
| Take before sex | About 1 hour | At least 30 minutes | About 1 hour |
| Effect window | About 4 hours | Up to 36 hours | About 4–5 hours |
| Label starting dose | 50 mg | 10 mg on demand, or 2.5–5 mg daily | 10 mg |
| Maximum frequency | Once a day | Once a day | Once a day |
| Heavy fatty meal | Can delay onset | Little effect | Can reduce effect |
| Daily option | No | Yes | No |
| Also approved for BPH | No | Yes (5 mg daily) | No |
How ED tablets work
All three medicines block an enzyme called PDE5. This helps the blood vessels in the penis relax and fill with blood when you are sexually aroused. They do not cause an erection on their own and do not increase sexual desire – arousal is still needed. Differences between them come down to how quickly they are absorbed and how long they stay active in the body.
Who should not take ED tablets
- Anyone using nitrates in any form, including GTN spray, isosorbide mononitrate or dinitrate, and recreational ‘poppers’.
- Anyone taking riociguat for pulmonary hypertension.
- People who have had a heart attack or stroke in the last 6 months, or who have unstable angina, very low blood pressure or uncontrolled high blood pressure, unless a specialist approves.
- People with certain inherited eye conditions such as retinitis pigmentosa.
- Anyone already taking another PDE5 inhibitor, including sildenafil prescribed for pulmonary hypertension.
ED can be an early heart-health warning
Erection problems often share causes with heart disease – narrowed blood vessels, diabetes, high blood pressure, high cholesterol and smoking. Because the penile arteries are smaller than the heart’s arteries, ED can appear years before heart symptoms. Read why ED is often the first sign of heart disease and ask your doctor for a blood pressure, cholesterol and blood sugar check.
Side effects of ED tablets
The most common side effects are headache, facial flushing, a blocked or runny nose and indigestion. Tadalafil can also cause back pain or muscle aches, and sildenafil can briefly tint vision blue or make it more sensitive to light. Seek urgent medical help for an erection lasting more than 4 hours, sudden loss of vision in one or both eyes, sudden hearing loss, or chest pain during sex.
How to get the best results
- Take it at the right time before sex and allow for arousal – the tablet does not work on its own.
- For sildenafil and vardenafil, avoid a heavy, fatty meal just before the dose.
- Keep alcohol light. Heavy drinking makes erections harder and increases dizziness.
- Give it several tries at the correct dose before deciding it does not work. If it still fails, ask your prescriber about the dose or another option – see 11 reasons Viagra may not work.
- Never take more than one dose in 24 hours or combine two ED medicines.
Avoid fake and ‘herbal’ ED products
The FDA regularly finds hidden sildenafil and tadalafil in products sold as natural or herbal sexual enhancers, sometimes at unsafe doses and without warnings about nitrates. Learn the 12 warning signs of fake Viagra and the 2026 FDA hidden-ingredient warnings.
ED tablets at label strengths
Your prescriber chooses the medicine and strength. Prices and stock are shown on each product page.
Sildenafil (generic Viagra)
Tadalafil (generic Cialis)
Vardenafil (generic Levitra)
Related men’s health guides
ED medication FAQs
Which ED tablet lasts the longest?
Tadalafil. Its effect can last up to 36 hours, compared with about 4 to 5 hours for sildenafil and vardenafil.
Which ED tablet works the fastest?
All three can start working in about 30 minutes in some people. Labels advise taking sildenafil and vardenafil about an hour before sex and tadalafil at least 30 minutes before.
Can I take sildenafil and tadalafil together?
No. Combining two PDE5 inhibitors increases the risk of low blood pressure and side effects without proven extra benefit.
Why can’t ED tablets be taken with nitrates?
Both widen blood vessels. Together they can cause a sudden, dangerous drop in blood pressure, so the combination is contraindicated on every PDE5 inhibitor label.
Is daily tadalafil better than on-demand?
Daily low-dose tadalafil removes the need to plan around sex and also treats enlarged-prostate urinary symptoms. On-demand dosing suits people who have sex less often. Your prescriber can help decide.
Does food affect ED tablets?
A heavy, high-fat meal can delay sildenafil and reduce the effect of vardenafil. Tadalafil is not meaningfully affected by food.
Can I drink alcohol with ED tablets?
Heavy drinking makes erections harder to achieve and, with PDE5 inhibitors, increases the chance of dizziness and low blood pressure. Keep alcohol light.
What if it does not work the first time?
Labels note that several attempts at the right dose and timing may be needed. Arousal is still required. If it keeps failing, talk to your prescriber about the dose or another option.
Is generic sildenafil the same as Viagra?
Generic sildenafil contains the same active ingredient as Viagra. Approved generics must deliver the same amount of medicine to the bloodstream within strict limits.
Do ED tablets increase sexual desire?
No. They improve blood flow when you are aroused but do not change libido. Low desire can have other causes, such as low testosterone, stress or relationship factors.
Taking other medicines?
Check them against sildenafil or tadalafil in under a minute.
Sources & official guidelines
- FDA label – Viagra (sildenafil), DailyMed
- FDA label – Cialis (tadalafil), DailyMed
- FDA labels – vardenafil, DailyMed
- NHS – Erectile dysfunction
- NIH NIDDK – Erectile dysfunction
- American Urological Association – Clinical guidelines
- FDA – Tainted sexual enhancement products
