| Sildenafil | Tadalafil | Vardenafil | Avanafil | |
|---|---|---|---|---|
| Brand names | Viagra, Viagra Connect | Cialis, Cialis Together | Levitra | Spedra |
| Available generically | Yes | Yes | Yes | No |
| Starting dose | 50mg | 10mg | 10mg | 100mg |
| Time taken to start working | 30-60 minutes | 30-60 minutes (2.5mg and 5mg tablets can be taken daily) | 25-60 minutes - faster for orodispersible tablets | 15-30 mins on empty stomach, 1.5 hours on full stomach |
| How long effects last | 4 hours | 36 hours | 4-5 hours | 4 hours |
| Warnings and cautions | ||||
| Warning | Sildenafil | Tadalafil | Vardenafil | Avanafil |
| Do not take | Allergic to ingredients, low or high blood pressure, severe heart or liver problems, loss of vision due to NAION, recent stroke or heart attack | |||
| Rare inherited eye diseases | Kidney dialysis, rare inherited eye diseases | Liver or kidney problems, rare inherited eye diseases | ||
| Exclusions - talk to your doctor first | Sickle cell anaemia, multiple myeloma, leukaemia, deformity of the penis, problems with your heart, stomach ulcer or bleeding problems | |||
| Drug interactions | Any nitrate-based medication, usually to treat angina (important); 'poppers'; nitric oxide donors, medicines for HIV, AIDS, or fungal infections; riociguat; alpha-blockers; other ED medicines | |||
| Common side effects (% occurrence) | ||||
| Adverse event | Sildenafil | Tadalafil | Vardenafil | Avanafil |
| Headache | 12.8% | 14.5% | 16% | 9.3% |
| Flushing | 10.4% | 4.1% | 12% | 3.7% |
| Dyspepsia (indigestion) | 4.6% | 12.3% | 4% | uncommon |
| Nasal congestion | 1.1% | 4.3% | 10% | 1.9% |
| Dizziness | 1.2% | 2.3% | 2% | 0.6% |
| Abnormal vision | 1.9% | < 2% | none | |
| Back pain | 6.5% | < 2% | ||
| Myalgia (muscle pains) | 5.7% | < 2% | ||
| Medical emergencies (very rare) | ||||
| Urgent medical attention required | Sudden decrease or loss of vision, Priapism (painful erection lasting 2 hours or more), allergic reaction, chest pains, heart attack | |||
Notes: Sexual stimulation is required before erection will take place. See the manufacturer's patient information leaflet included in medicine packs for full details of cautions and interactions. If side effects are severe stop the medication and see your doctor.