Viagra vs Cialis vs Levitra vs Stendra: Which ED Medication Is Right for You?
Viagra (sildenafil), Cialis (tadalafil), Levitra (vardenafil), and Stendra/Spedra (avanafil) are the four MHRA-approved oral medications for erectile dysfunction available in the UK. All four belong to the same drug class — phosphodiesterase type 5 (PDE5) inhibitors — and work through the same underlying mechanism. But they differ in meaningful ways: how quickly they work, how long they last, whether food affects them, and their side effect profiles. This guide compares all four.
Medical disclaimer: This article is for informational purposes only. ED treatments are prescription-only medicines. Always complete a clinical consultation before use. Our prescribers are GPhC-registered pharmacist independent prescribers.
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How PDE5 Inhibitors Work
All four medications inhibit the PDE5 enzyme, which regulates blood flow in the penis. When you are sexually stimulated, the body releases nitric oxide, triggering production of cGMP — a signalling molecule that causes smooth muscle in penile blood vessels to relax, allowing blood to flow in and produce an erection. PDE5 breaks cGMP down. By blocking PDE5, these drugs allow the erection response to occur more easily and more reliably.
Important: None of the four medications cause automatic erections. Sexual stimulation is required with all of them. They enhance the body’s natural response to arousal — they do not replace it.
Full Comparison: All Four Medications
| Viagra (Sildenafil) | Cialis (Tadalafil) | Levitra (Vardenafil) | Stendra/Spedra (Avanafil) | |
|---|---|---|---|---|
| Onset | 30–60 min | 30 min | 25–60 min | 15–30 min |
| Duration | 4–6 hours | Up to 36 hours | 4–6 hours | Up to 6 hours |
| Affected by food? | Yes — avoid fatty meals | No | Mildly | Minimal |
| Daily option? | No | Yes (5mg) | No | No |
| Clinical efficacy | ~82% | ~81% | ~80% | ~77% |
| Generic available? | Yes | Yes | Yes | No (branded only) |
| Key advantage | Best-known; cheapest generic | Longest duration; spontaneity | For men who don’t respond to sildenafil | Fastest onset overall |
Sildenafil (Viagra) — Best For: On-Demand Use, Cost
Sildenafil has been in use since 1998 and has the longest evidence base of any ED medication. It works within 30–60 minutes and lasts 4–6 hours. Its main limitation is food sensitivity — a large, fatty meal can delay and reduce its effect significantly.
Best suited to: Men who plan sexual activity in advance and want the most cost-effective on-demand option. Generic sildenafil is the lowest-cost ED treatment available in the UK. For a detailed head-to-head with tadalafil, see: Tadalafil vs Sildenafil.
Tadalafil (Cialis) — Best For: Spontaneity, Frequent Sex
Tadalafil’s 36-hour duration sets it apart from every other ED medication. It is not affected by food and is available as a once-daily low dose (5mg) for continuous treatment. Studies consistently show the highest partner preference scores of any ED medication.
Best suited to: Men who want the most spontaneous sexual experience, or who have sex more than twice a week (daily 5mg is often more cost-effective). Daily tadalafil also has a dual licence — it is approved for both ED and benign prostatic hyperplasia (BPH), making it the preferred choice for men with both conditions.
Vardenafil (Levitra) — Best For: Men Who Don’t Respond to Sildenafil
Vardenafil’s pharmacological profile is similar to sildenafil, with slightly different receptor selectivity that may be beneficial for some men who do not respond adequately to sildenafil.
Best suited to: Men for whom sildenafil is ineffective or poorly tolerated after trying it at the correct dose under optimal conditions.
Important Caution
Vardenafil is associated with QT interval prolongation. It must not be used by men with long QT syndrome or by those taking medicines that prolong the QT interval (certain antiarrhythmics, some antibiotics). Your prescriber will screen for this.
Avanafil (Spedra/Stendra) — Best For: Fastest Onset
Avanafil is the newest of the four MHRA-approved ED medications and has the fastest onset — it can work in as little as 15–30 minutes. It is also highly selective for PDE5, which may mean a lower incidence of some side effects (particularly visual disturbances and nasal congestion) compared to sildenafil.
Best suited to: Men who want the shortest possible lead time before sexual activity. Currently available in branded form only (Spedra) — no generic equivalent is available in the UK.
Side Effects: What All Four Have in Common
As all four are PDE5 inhibitors, their side effect profiles overlap significantly. Common side effects across all four include headache, facial flushing (warmth and redness, usually in face and chest), nasal congestion or runny nose, indigestion or mild nausea, and dizziness.
| Medication | Notable Side Effects |
|---|---|
| Sildenafil | Visual disturbances (blue tinge, increased light sensitivity) more common than with other agents |
| Tadalafil | Back pain and muscle aches (myalgia) — related to long systemic presence; typically resolves within 48 hours |
| Vardenafil | QT prolongation risk — requires cardiac history screening |
| Avanafil | Generally well tolerated; lowest rate of visual disturbances of the four |
Seek Emergency Care If
After taking any ED medication, you experience: an erection lasting more than 4 hours (priapism — go to A&E immediately), sudden loss of vision in one or both eyes, sudden hearing loss, or chest pain. These are rare but require urgent treatment.
Interactions: What All Four Share
- Nitrate medicines (absolute contraindication): GTN spray or patches, isosorbide mononitrate or dinitrate, recreational “poppers” (amyl nitrite). The combination causes a severe and potentially fatal blood pressure drop.
- Alpha-blockers (used for prostate or blood pressure): additive blood-pressure-lowering effect — dose adjustment and timing advice required.
- CYP3A4 inhibitors: Certain antibiotics (clarithromycin, erythromycin) and antifungals (ketoconazole, itraconazole) increase blood levels of all four drugs. Start at the lowest dose.
- Grapefruit juice: Inhibits CYP3A4 metabolism — avoid with all four.
Making the Decision
For most men starting ED treatment, the choice comes down to sildenafil or tadalafil. The key question is spontaneity: if you are happy to plan sexual activity around a medication window, sildenafil is the most cost-effective choice. If you want a more natural experience without timing constraints, tadalafil — particularly the daily 5mg option — is worth considering.
Vardenafil and avanafil are valuable alternatives for men who do not respond to sildenafil or for whom specific pharmacological properties are better suited. Access Doctor’s pharmacist independent prescribers can advise on the best option for your circumstances during your online consultation.
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Frequently Asked Questions
What is the difference between Viagra, Cialis, Levitra, and Stendra?
All four are PDE5 inhibitors that treat ED by increasing blood flow to the penis when sexually stimulated. Key differences are duration of action (Viagra 4–6 hours, Levitra 4–6 hours, Stendra up to 6 hours, Cialis up to 36 hours), onset speed (Stendra fastest at 15–30 minutes), and food sensitivity (Cialis unaffected by food; Viagra significantly affected by fatty meals).
Which ED medication is most effective?
All four have comparable effectiveness in clinical trials: sildenafil ~82%, tadalafil ~81%, vardenafil ~80%, avanafil ~77%. No single medication is consistently more effective than the others — the right choice depends on lifestyle fit, tolerance, and personal preference.
Which ED medication lasts the longest?
Tadalafil (Cialis) — up to 36 hours. It is also available as a once-daily 5mg dose for continuous treatment, which eliminates on-demand timing entirely.
Which ED medication works fastest?
Avanafil (Spedra/Stendra) — typically 15–30 minutes. Vardenafil and tadalafil also work slightly faster than sildenafil on average.
Can I drink alcohol with ED medication?
Small amounts (1–2 units) are generally acceptable with all four, but larger quantities impair erectile function independently and amplify the blood-pressure-lowering effect. Grapefruit juice should be avoided with all four as it affects drug metabolism.
Do I need a prescription for Viagra in the UK?
Sildenafil 50mg (Viagra Connect) can be purchased without a prescription from registered pharmacies for men aged 18–64. All other doses and all other ED medications require a prescriber consultation. Access Doctor provides this online without a GP appointment.
References
- NICE. Erectile dysfunction — management. CKS 2023. cks.nice.org.uk
- NHS. Erectile dysfunction. nhs.uk
- GPhC. Standards for registered pharmacies. pharmacyregulation.org
- Hatzimouratidis K et al. EAU Guidelines on erectile dysfunction. Eur Urol. 2010.
- Goldstein I et al. Oral sildenafil in the treatment of erectile dysfunction. NEJM 1998.
- Carson CC et al. Tadalafil for erectile dysfunction. BJU Int. 2004.