Viagra Connect side effects: what's common, what's serious and what's known long term
- Viagra Connect side effects: key takeaways
- Common side effects and how often they happen
- Why do these side effects happen?
- How long do side effects last, and how can you reduce them?
- Serious side effects: stop and seek urgent help
- Long-term side effects: what does the evidence say?
- Interactions that increase risk
- How do side effects compare with other ED tablets?
- Reporting side effects
- Conclusion
Viagra Connect side effects: key takeaways
- Most side effects are mild and short-lived. The most common are headache, facial flushing, a stuffy nose and indigestion.
- Headache is the only side effect listed as very common, affecting more than 1 in 10 people.
- Get urgent help for an erection lasting over 4 hours, sudden vision or hearing loss, chest pain or a severe allergic reaction.
Common side effects and how often they happen
The SmPC groups side effects into frequency bands: very common (more than 1 in 10 people), common (up to 1 in 10) and uncommon (up to 1 in 100).
| SmPC frequency | Side effects |
|---|---|
| Very common (more than 1 in 10) | Headache |
| Common (up to 1 in 10) | Dizziness, facial flushing or hot flush, stuffy nose, nausea, indigestion, colour tinge to vision, blurred vision or other visual disturbance |
| Uncommon (up to 1 in 100) | Runny nose, nosebleed, vomiting, heartburn, dry mouth, rash, muscle pain, sleepiness, vertigo, ringing in the ears, fast or pounding heartbeat, high or low blood pressure, eye pain or redness, tiredness, chest pain, allergic reaction |
Source: SmPC, section 4.8. The full list, including rare effects, is in the SmPC and leaflet.
Why do these side effects happen?
Sildenafil blocks an enzyme called phosphodiesterase type 5 (PDE5), which normally breaks down cGMP, the messenger that relaxes smooth muscle in the penis's blood vessels during arousal. With PDE5 blocked, cGMP lasts longer and blood flows in more easily.
Sildenafil also widens blood vessels elsewhere, enough to cause a small, temporary drop in blood pressure. Wider vessels in the head, face and lining of the nose are the usual explanation for headache, flushing and a stuffy nose.
Visual tinting has a different cause. Sildenafil is around 10 times more selective for PDE5 than for PDE6, a related enzyme in the retina's light-sensing cells, so it partly blocks PDE6 too, which can briefly affect blue and green colour vision. In studies at 100mg (twice the Viagra Connect dose), mild colour changes were seen 1 hour after the dose and were no longer evident at 2 hours.
How long do side effects last, and how can you reduce them?
Sildenafil has a half-life of 3 to 5 hours, so the amount in your body roughly halves over that time. Common side effects tend to ease as it clears, though the leaflet gives no set timeframe.
Tip:
According to NHS guidance:
- Take no more than one tablet a day.
- Avoid grapefruit and grapefruit juice, which can make side effects more likely.
- Avoid large amounts of alcohol before sex.
- Don't drive, cycle or use machinery while you feel dizzy or your vision is blurred.
- If the effect feels too strong or side effects bother you, speak to a pharmacist or your GP rather than changing how you take it.
Viagra Connect comes in one strength. If it doesn't suit you, a UK-registered prescriber can assess whether prescription sildenafil at a different strength is appropriate.
Serious side effects: stop and seek urgent help
Stop taking Viagra Connect and get medical help straight away if you have:
- An erection lasting more than 4 hours (priapism). Delay risks permanent damage.
- Sudden decrease or loss of vision in one or both eyes.
- Sudden hearing loss, listed as a rare side effect.
- Chest pain before, during or after sex. Sit in a semi-upright position, try to relax and don't use nitrates to treat it.
- A severe allergic reaction, such as sudden wheeziness, difficulty breathing or swelling of the face, lips or throat.
Important: when to call 999 or NHS 111
Call 999 if:
- you have chest pain that feels tight or heavy, with shortness of breath or sweating
- your lips, mouth, throat or tongue suddenly swell, or you're struggling to breathe
- you have a seizure (fit)
Call NHS 111 if:
- you think you have another serious side effect
- you've taken more than one tablet in a day
If you're told to go to A&E, don't drive yourself.
Long-term side effects: what does the evidence say?
The NHS states that sildenafil is safe to take for a long time, with no apparent lasting harmful effects over many months and years. The SmPC reports that safety and efficacy were maintained in long-term studies, including in men who kept taking it for a year or more.
Neither source mentions the medicine becoming less effective over time or people becoming dependent on it. That isn't the same as proof it can't happen, and there's less data on use beyond a year.
Good to know:
The leaflet advises seeing your GP within 6 months of starting, as erectile dysfunction can be an early sign of heart disease, diabetes, high blood pressure or high cholesterol. Go sooner if the tablets haven't worked after several attempts or symptoms worsen.
Interactions that increase risk
- Nitrates and "poppers": never combine with nitrates such as GTN, nicorandil or amyl nitrite, as blood pressure can drop dangerously.
- Riociguat: must not be combined, as blood pressure can drop.
- Ritonavir: must not be combined. It raised sildenafil levels about 11-fold in studies.
- Other CYP3A4 inhibitors: ketoconazole, itraconazole, erythromycin and cimetidine raise sildenafil levels. Check with a pharmacist first.
- Alpha blockers: doxazosin, tamsulosin and alfuzosin can lower blood pressure with sildenafil, most likely within 4 hours. You should be stable on your alpha blocker first.
- Alcohol: didn't add to the blood pressure drop in healthy volunteers, but large amounts can make erections harder.
- Grapefruit: may modestly raise sildenafil levels.
How do side effects compare with other ED tablets?
| Medicine | Common side effects | When it can be taken before sex |
|---|---|---|
| Viagra Connect (sildenafil 50mg) | Headache, dizziness, flushing, stuffy nose, nausea, indigestion, visual changes | About 1 hour before, up to 4 hours |
| Tadalafil | Headache, nausea, flushing, indigestion, stuffy nose, muscle aches | Up to 36 hours |
Muscle aches are common with tadalafil but uncommon with sildenafil.
Reporting side effects
You can report suspected side effects through the MHRA Yellow Card scheme, online or via the Yellow Card app. Reports help build a clearer picture of a medicine's safety.
Conclusion
Viagra Connect side effects are usually mild and short-lived. Knowing the urgent warning signs, checking interactions and booking a GP review within 6 months all help you use it safely. If it doesn't suit you, DoktorABC's UK-registered prescribers can review whether a prescription treatment may be appropriate.
FAQ
How long do Viagra Connect side effects last?
There's no set time, but common effects tend to ease as the medicine clears.
Does Viagra Connect stop working over time?
No tolerance is reported in the SmPC or NHS guidance, and effectiveness was maintained in follow-on studies of a year or longer.
Is a blue tinge to my vision normal?
A colour tinge is common and usually temporary. Sudden vision loss needs urgent help.
Can I drink alcohol with Viagra Connect?
Small amounts are unlikely to add to side effects, but large amounts can make erections harder.
Do I need to see a GP?
Yes, within 6 months of starting.
The DoktorABC medical advisory board
Dr. Roland Ruiken
Medical advisor, Norway
Dr. Viktor Simunovic
Medical advisor, Croatia