Little Calvin Muteesa is only 2 years old but he takes Viagra four times a day — and without it he would die.

Calvin was first prescribed the impotence drug when he was just three months old.

Now he is believed to be Britain’s youngest regular Viagra user, having taken the drug — for up to six times a day — for the past 30 months.

Calvin has pulmonary arterial hypertension, a rare condition that causes his blood pressure to be dangerously high. This starves his lungs of oxygen-rich blood.

The youngster struggles for breath and his heart has to work twice as hard to force blood to his lungs. Viagra relaxes his pulmonary artery, which carries blood to the lungs, and allows more blood and oxygen through.

“When I first saw the packet I didn’t know what to think,” Calvin’s mother Maureen said.

“I asked the nurse, ‘Why on earth are you giving my son that?' It’s for something completely different. But you could see the difference as soon as he started taking it. It was amazing.”

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