Sildenafil vs tadalafil: two PDE5 inhibitors used in authorised, prescription-only medicines for erectile dysfunction. Both rely on sexual stimulation to work, and both carry the same hard interaction rule: they must not be combined with nitrate medicines. Their main practical differences sit in the usual time profile and the effect of food — and neither substance is universally better than the other. A doctor decides suitability per person, against one specific registered medicine.
Still, comparing the two is not scoring a race with a guaranteed winner. It is closer to choosing between two umbrellas for different weather — the forecast and the person matter more than the logo on the canopy.
Prepared by Testovic, editorial author, without a documented health qualification and without an independent professional reviewer.
Warning: this article is for information only and does not replace a doctor or pharmacist. Registration and prescription status apply to a specific medicine and pack, not to a substance name. Verify the exact medicine in the database of your national medicines authority, obtain it only through permitted channels, and consult a health professional before any use. If you suspect a falsified product, see our procedure for suspected falsified medicine.
Comparison at a glance
| Feature | Sildenafil | Tadalafil |
|---|---|---|
| Authorised tablet strengths | 25 mg, 50 mg, 100 mg (Viagra EPAR overview) | 2.5 mg, 5 mg, 10 mg, 20 mg (Cialis EPAR overview) |
| When to take it (authorised directions) | About 1 hour before; timing varies (Viagra EPAR overview, NHS sildenafil guidance) | At least 30 minutes before (Cialis EPAR overview, NHS tadalafil guidance) |
| Nitrates | Contraindicated (Viagra EPAR overview, NHS sildenafil guidance) | Not usually prescribed together (NHS tadalafil guidance) |
| Prescription status (EU) | Only with a prescription (Viagra EPAR overview) | Only with a prescription (Cialis EPAR overview) |
Each cell above follows the linked authorised document — EPAR overviews for strengths, prescription status and sildenafil–nitrate contraindication; EPAR dosing directions and NHS pages for timing; NHS pages for the tadalafil–nitrate caution. Rows the retrieved overviews do not cover (such as exact duration figures) are left out of this table on purpose. A doctor matches the substance, strength and schedule to the individual.
Sildenafil and tadalafil in brief
| Property | Sildenafil | Tadalafil |
|---|---|---|
| Class | PDE5 inhibitor | PDE5 inhibitor |
| Condition for effect | sexual stimulation required | sexual stimulation required |
| Usual time profile | shorter | longer |
| Effect of food | a fatty meal can delay onset | usually smaller |
| Reference-medicine strengths for ED | up to 100 mg | 2.5, 5, 10 and 20 mg |
| Key shared restriction | nitrates must not be combined | nitrates must not be combined |
None of these rows is a recommendation. The table compares documented properties of authorised reference medicines; it cannot tell you which — or whether — either substance suits you.
How they work: the same basic mechanism
Both substances block the enzyme phosphodiesterase type 5 (PDE5). With sexual arousal, the body releases nitric oxide in penile tissue, which raises cGMP — a substance that relaxes smooth muscle and widens blood vessels. Blocking PDE5 lets cGMP act longer, supporting blood flow. The condition stays the same for both: without sexual stimulation, neither substance creates an erection.
(Sources: NHS: sildenafil medicine information, European Medicines Agency – Viagra, European Medicines Agency – Cialis)
Sildenafil vs tadalafil: time profile and food
Sildenafil usually starts working within 30 to 60 minutes after taking it. A fatty meal can push onset towards 90 minutes and weaken the effect. Its usual action window is about 4 to 6 hours.
Tadalafil is known for a longer time profile than sildenafil. The exact onset and duration depend on the dose, health status, other medicines and the specific registered product — which is why no exact number of hours is quoted here as a promise.
Food separates them more clearly than minutes do: a heavy, fatty meal measurably delays sildenafil, while the food effect for tadalafil is usually smaller.
(Sources: Mayo Clinic – ED treatment options, PubMed – comparison of PDE5 inhibitors, NHS – sildenafil, NHS – tadalafil)
Sildenafil vs tadalafil dosing frameworks: orientation, not instruction
Regulators assess doses for a specific medicine and indication, not for a substance nickname. For orientation only:
- Authorised sildenafil (Viagra) for erectile dysfunction comes in strengths of 25, 50 and 100 mg; 100 mg is the maximum single dose for this indication.
- Authorised tadalafil (Cialis) for erectile dysfunction comes in strengths of 2.5, 5, 10 and 20 mg. The EMA lists a recommended on-demand dose of 10 mg taken at least 30 minutes before sexual activity, which a doctor may increase to 20 mg, with a maximum of one dose per day. A daily regimen of 5 mg or 2.5 mg exists for suitable patients, and continuous daily use of the 10 or 20 mg strengths is not recommended.
These frameworks belong to specific registered medicines. They are not dosing advice and they do not transfer to unregistered products; the right choice for you therefore belongs to a doctor.
(Sources: European Medicines Agency – Viagra, European Medicines Agency – Cialis)
Why “which is stronger?” is the wrong question
Milligram numbers are not comparable across different substances. Each has its own authorised dose range, its own pharmaceutical data and its own response profile, so “80 beats 50” is arithmetic, not medicine. A bigger number on a box says nothing about suitability — for example, our article on high-dose sildenafil shows why twice the dose is not twice the effect.
Sildenafil vs tadalafil: side effects and combinations
Authorised medicines in this class commonly list headache, flushing and digestive upset. The EMA also lists back and muscle pain for tadalafil, and notes that side effects can be more frequent at higher doses.
Never combine either substance with nitrate medicines or with riociguat; such combinations can cause a dangerous drop in blood pressure. Alcohol can worsen dizziness and blood-pressure effects. Seek prompt medical help for chest pain, sudden loss of vision, collapse, a severe allergic reaction, or an erection lasting more than four hours.
(Sources: NHS – sildenafil, NHS – tadalafil, European Medicines Agency – Cialis)
Unregistered product names change nothing
Internet shops sell many products named after these substances. A name on a box does not transfer the registration, the tested composition or the authorised dosing framework of a medicine to that box. Therefore, check the registration of any specific product in your national medicines authority’s database and the seller against the list of entities permitted to sell medicines online. Our verification guide walks through both checks step by step.
What this comparison cannot tell you
- which of the two substances suits you;
- how you personally will respond to either;
- whether a specific pack bought online is authentic;
- the current registration status of a specific product name.
Those questions need a health professional and the regulator’s database — not a comparison table.
Sources and methodology
- European Medicines Agency – Viagra (sildenafil) — authorised indications, strengths and safety information.
- European Medicines Agency – Cialis (tadalafil) — authorised strengths, dosing framework and side effects.
- NHS – sildenafil and NHS – tadalafil — plain-language medicine information.
- Mayo Clinic – ED treatment options — treatment-choice context.
- PubMed – comparison of PDE5 inhibitors and NHS: sildenafil medicine information — pharmacological background.
Method, limits and corrections: how we create and update content.
Sildenafil vs tadalafil: frequently asked questions
Strength cannot be compared by milligram numbers across different substances. Each has its own authorised dose range for a specific medicine; a doctor judges fit for the person, not the bigger number.
Tadalafil has the longer usual time profile; sildenafil’s typical window is around 4 to 6 hours. Individual response varies with dose, health status and the specific registered medicine.
Not on your own initiative. Combining PDE5 inhibitors can increase the risk of a blood-pressure drop and other side effects. A treatment plan belongs to a doctor.
Registered medicines containing either substance are prescription-only in the EU. The status of any specific product must be verified in the regulator’s database.
A fatty meal can delay sildenafil’s onset; the food effect for tadalafil is usually smaller. Follow the leaflet of the specific medicine you have actually been prescribed.
Only with professional guidance. Interactions, contraindications and dose frameworks differ between the substances, and the decision depends on diagnosis and health status.
Summary
- Same class, different profiles: sildenafil acts for a shorter window and is sensitive to fatty food; tadalafil has a longer usual profile with a smaller food effect.
- Both require sexual stimulation, both exclude nitrates, and registered medicines with either substance are prescription-only.
- Neither is universally better. Diagnosis, other medicines and the specific registered product decide — with a doctor.
Where to go next: the complete sildenafil guide goes deeper into one substance, the tadalafil guide covers the other side of this comparison, and Super Vidalista shows why combining active substances multiplies the cautions. If sildenafil itself does not seem to work, what to check when sildenafil does not work walks through timing, food and the prescriber checklist. For a personal health question, a doctor or pharmacist — not this page — holds the answer. If brand names blur together, the product finder narrows the catalogue by need instead of by name.
Further informational articles can be found on the blog.
