'Merci, periactin!' French TikTokers credit hayfever drug for helping enhance their breasts and bums - but experts warn the antihistamine is being 'misused' for weight gain

Periactin, the market name for cyproheptadine, is being used for cosmetic purposes 

You've heard of a diabetes drug being used to lose weight; but it's the antihistamine helping people gain weight that is causing a stir in Europe.

Periactin, the name commonly used for the drug cyproheptadine, is being touted by TikTok users in France and the US for helping them achieve sultry curves - including bigger bums and boobs.

Across the social media platform women are crediting their use of the drug with giving them hourglass figures with defined, curvaceous hips - but experts are warning people who want to gain weight that the antihistamine isn't the answer.

The Telegraph reports the drug is being pulled from shelves all over France after social media exploded with TikTok influencers hailing the drug for helping them grow their derriéres.

And it's not just in France that the drug has taken off - as influencers in the US are also encouraging people to take periactin to gain weight.

A common, over-the-counter drug for hayfever is being touted by TikTokers as helping them enhance their boobs and bums. Pictured: US TikToker Avi, who says periactin helped her gain weight

Periactine is an over-the-counter antihistamine that relieves a variety of allergy-related symptoms including itching and rashes, vomiting, sneezing and coughing.

However in the past, it has also been used to encourage weight gain due to its side effect which increases the appetite.

And patient reviews appear to corroborate the drug's use for the purpose of weight gain, with people taking to WebMD to credit periactin with helping them put on the pounds.

One young woman who revealed she took the drug for loss of appetite said she gained 'almost a pound a day' when taking just one periactin pill per day.

French TikToker Romy hailed the benefits of periactin which she says helped her gain 10 kilos - and stressed to her followers that they should not fear its side effects

Fellow TikTok user Mayreen claimed she had managed to gain nine kilos in just one month and said 'merci periactin' as she credited the drug with doing so

She claimed she went from 94lbs to 125lbs while taking the drug, but then dropped back down to 110lbs after four months of not taking it.

An influencer based in the US named Avi revealed in a clip on her TikTok channel that she had gained weight after taking periactin because it had increased her appetite.

Posting a clip where she's sitting in the passenger seat of a car, Avi, who suffers from the eating disorder ARFID, reveals taking the drug has helped her eat more than once a day.

She posted the clip with the caption: 'I have new stretch marks!!!!'

A viewer asked Avi if she recommended the drug to gain weight; after her own doctors had suggested periactin.

Avi replied: 'Yes! I have to take it at night bc it makes me tired af but otherwise zero issues with it.'

But it's in France that the drug is taking TikTok by storm - prompting France's national agency for the safety of medicines to ban it as an over-the-counter drug.

From July 10, periactin will only be available by prescription in France; much to the dismay of the hundreds of women who are using the antihistamine to enhance their assets.

As per the Telegraph, a statement released by the agency this week read: 'As part of our ongoing efforts to promote the proper use of medicines, and to prevent their misuse for cosmetic weight gain, we are changing the conditions for prescribing and dispensing cyproheptadine.

'Despite the information measures put in place since 2022, this misuse persists, as do the associated risks. Changes to prescribing and dispensing conditions are designed to limit this misuse.'

A French TikToker named Romy took to the platform last year to promote the drug, which she says helped her gain 10 kilos.

In the caption on her video, she encouraged viewers not to fear the side effects of taking the drug, which can include hallucinations, insomnia and palpitations.

Another TikToker named Mayreen claimed she had managed to gain nine kilos in just one month thanks to the drug - and posted a clip on TikTok saying 'merci periactin'.