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Men can now buy the impotence pill Viagra Connect without a prescription at some UK pharmacies.

Health experts hope it will mean more men get help for erectile dysfunction - a condition thought to affect up to one in five adult men, 4.3 million in the UK.

Like any medication though, the drug can cause side-effects and should not be misused or abused.

What should men consider before buying and trying the little blue pills?

Who can have it?

Viagra Connect is only for men who have impotence.

No-one under the age of 18 can buy it, although women might be able to buy it on behalf of their partner if the pharmacist is satisfied it is appropriate to dispense it.

And it will not be sold to men who are not medically fit enough to have sex. This includes men with severe heart or blood vessel problems.

As a rule of thumb, men who become very breathless or experience chest pain when doing light exercise, such as climbing two flights of stairs, should not take these pills.

Can it be bought off the shelf?

No. You will need to ask the pharmacist for it, who will then check it is safe for you to take.

A packet of four pills will cost £19.99.

Do men wanting to buy have to talk to someone and be examined?

You can ask at the pharmacy counter for a quiet word or to have a conversation in a private room if they prefer - most pharmacies now have private consultation facilities.

The pharmacist will ask about symptoms, general health, and any other medications you might be taking. They should not ask personal questions about your sex life or sexual preferences.

You should not need a physical examination.

Will it work?

In many cases yes, but it is not effective for everyone.

The drug relaxes the blood vessels in the penis to help blood flow and will help achieve an erection in response to sexual stimulation.

It can be taken with or without food, although it may take a little longer to start working if you have just had a big meal.

You should take it about an hour before you plan to have sex.

Do not take it with grapefruit or grapefruit juice, because this can affect how the medicine works.

And do not take more than one 50mg tablet per day.

If it has been some time since you were able to get or keep an erection, it may take a couple of attempts before you are able to achieve one.

Drinking lots of alcohol can also make it more difficult to get an erection.

What if it is too strong?

Talk to your pharmacist or doctor if you think it is too strong - the drug's effects last too long or are too powerful.

Prolonged and sometimes painful erections lasting longer than four hours have been occasionally reported by men taking the drug.

Although unlikely, if this does happen, seek immediate medical assistance.

What other side-effects might there be?

Very common (may affect more than one in 10 people):

headache

Common (may affect up to one in 10):

dizziness

colour tinge to vision or blurred vision - some people start seeing a blue hue

hot flushes

blocked nose

nausea

Stop taking the pills and seek immediate medical attention if you have a serious side-effect such as:

chest pain

sudden decrease or loss of vision

an allergic reaction (eg difficulty breathing, wheeze and swelling of the lips, eyelids or face)

a seizure or fit

Drug clashes

People on nitrate pills for angina should not take Viagra Connect. That also goes for people taking recreational poppers (amyl nitrite).

There is also a clash with a medicine called riociguat and an HIV medication called ritonavir.

Make sure you tell the pharmacists about any treatments you are taking so they can check it will be safe for you to also have Viagra Connect.

Pharmacists should advise men to book a follow-up appointment with their doctor within six months of starting on Viagra Connect because erectile dysfunction can sometimes be a sign of other underlying conditions, including heart disease, high cholesterol and diabetes.

Can I get it anywhere else?

GPs can prescribe it. And some pharmacies will be selling it online, after a virtual consultation.

Always check that the seller is reputable. Drugs from unregulated sellers may be fake, ineffective and unsafe.