Molecule, a pill promising rapid weight loss, went viral on Russian TikTok earlier this year. Young people's feeds started filling up with captions like 'Take Molecule and forget food exists', and 'Do you want to sit in the back of the class in oversized clothes?'. Clips showed fridges lined with blue boxes featuring holograms and 'Molecule Plus' labels. The orders began piling in, as teenagers shared their 'weight-loss journeys' on social media. But there was a catch.

Maria, 22, had purchased the pill from a popular online retailer. She took two pills per day and, after two weeks, says her mouth dried up and she completely lost her appetite. 'I had absolutely no desire to eat, let alone drink. I was nervous. I was constantly biting my lips and chewing my cheeks.' Maria developed severe anxiety and began having negative thoughts. 'These pills were having a profound effect on my psyche,' she says. Maria, who lives in St Petersburg, says she wasn't prepared for such severe side effects.

Other TikTok users mentioned dilated pupils, tremors and insomnia. And at least three schoolchildren are reported to have ended up in hospital.

In April, a schoolgirl in Chita, Siberia, needed hospital care after overdosing on Molecule. According to local reports, she was trying to lose weight quickly, in time for the summer. The mother of another schoolgirl told local media that her daughter was admitted to intensive care after taking several pills at once. And in May, a 13-year-old boy from St Petersburg needed hospital care after experiencing hallucinations and panic attacks. He had reportedly asked a friend to buy him the pill because he was being teased at school about his weight.

Substance banned in UK, EU and US The packaging for Molecule pills often lists 'natural ingredients' such as dandelion root and fennel seed extract. But earlier this year, journalists at the Russian newspaper Izvestiya submitted pills they had purchased online for testing and found they contained a substance called sibutramine.

First used as an antidepressant in the 1980s and later as an appetite suppressant, studies later found sibutramine increased the risk of heart attacks and strokes - while only slightly promoting weight loss. It was banned in the US in 2010 and is also illegal in the UK, EU, China and other countries. In Russia, it is still used to treat obesity but is available only to adults and by prescription.

Purchasing and selling sibutramine without a prescription is a criminal offence. But that hasn't stopped individuals and small businesses from selling it online - often in higher doses than legal medication - and without requiring prescriptions. The unlicensed pills cost about £6-7 ($8-9) for a 20-day supply, much cheaper than recognized weight-loss injections like Ozempic, which on the Russian market sell for £40-160 ($50-210) per monthly pen.

'Weariness towards this market segment is missing,' says endocrinologist Ksenia Solovieva from St. Petersburg, warning of potential overdose risks, 'because we do not know how much of the active ingredient such 'dietary supplements' may contain.'

Russians regularly receive prison sentences for purchasing and reselling Molecule pills. But it's proving difficult for authorities to get a grip on the drug being sold illegally. A law was recently passed allowing authorities to block websites selling unregistered dietary supplements without a court order, yet sellers have been getting around this by categorizing them as 'sports nutrition'.

Online eating-disorder communities have become spaces where Molecule is promoted, with users relying on hashtags and coded terms to slip past moderation. Ms. Solovieva emphasized the danger to young people already struggling with eating disorders, as an easily available appetite suppressant can lead to serious health complications.

Maria now regrets her decision to use Molecule, having suffered severe side effects, and actively discourages others from trying it as she continues to see its promotion on TikTok.