Weight loss drug orlistat will go on sale as a pharmacy medicine under the brand Alli on April 22, GlaxoSmithKline has confirmed.

The manufacturer has promised “comprehensive, widespread training” to help pharmacists and pharmacy staff sell the much-anticipated product. This includes over 60 workshops for 7,000 attendees, as well as online distance learning.

He added: “Alli represents a real opportunity for overweight and obese people to benefit significantly from professional pharmacy intervention.”

The launch of Alli, which contains half the dose of prescription orlistat and claims to increase weight loss by 50 per cent compared with dieting alone.

Alli is a half-dose version of Orlistat prescription medicine Xenical and works by reducing the amount of fat the body absorbs from food.

Undigested fat is eliminated through bowel movements, which can cause side effects such as gas and oily discharge.