The average user of krokodil, a dirty cousin of morphine that is spreading like a virus among Russian youth, does not live longer than two or three years, and the few who manage to quit usually come away disfigured.
The active component is codeine, a widely sold over-the-counter painkiller that is not toxic on its own. But to produce krokodil, whose medical name is desomorphine, addicts mix it with ingredients including gasoline, paint thinner, hydrochloric acid, iodine and red phosphorous, which they scrape from the striking pads on matchboxes. In 2010, between a few hundred thousand and a million people, according to various official estimates, were injecting the resulting substance into their veins in Russia, so far the only country in the world to see the drug grow into an epidemic.
The "rotting" explains the drug's nickname. At the injection site, which can be anywhere from the feet to the forehead, the addict's skin becomes greenish and scaly, like a crocodile's, as blood vessels burst and the surrounding tissue dies. Gangrene and amputations are a common result, while porous bone tissue, especially in the lower jaw, often starts to dissipate, eaten up by the drug's acidity.
Russia has more heroin users than any other country in the world – up to two million, according to unofficial estimates. For most, their lot is a life of crime, stints in prison, probable contraction of HIV and hepatitis C, and an early death. As efforts to stem the flow of Afghan heroin into Russia bring some limited success, and the street price of the drug goes up, for those addicts who can't afford their next hit, an even more terrifying spectre has raised its head.
The home-made drug that Oleg and Sasha inject is known as krokodil, or "crocodile". It is desomorphine, a synthetic opiate many times more powerful than heroin that is created from a complex chain of mixing and chemical reactions, which the addicts perform from memory several times a day. While heroin costs from £20 to £60 per dose, desomorphine can be "cooked" from codeine-based headache pills that cost £2 per pack, and other household ingredients available cheaply from the markets.
It is a drug for the poor, and its effects are horrific. It was given its reptilian name because its poisonous ingredients quickly turn the skin scaly. Worse follows. Oleg and Sasha have not been using for long, but Oleg has rotting sores on the back of his neck.
"If you miss the vein, that's an abscess straight away," says Sasha. Essentially, they are injecting poison directly into their flesh. One of their friends, in a neighbouring apartment block, is further down the line.
"She won't go to hospital, she just keeps injecting. Her flesh is falling off and she can hardly move anymore," says Sasha. Photographs of late-stage krokodil addicts are disturbing in the extreme. Flesh goes grey and peels away to leave bones exposed. People literally rot to death.
Russian heroin addicts first discovered how to make krokodil around four years ago, and there has been a steady rise in consumption, with a sudden peak in recent months. "Over the past five years, sales of codeine-based tablets have grown by dozens of times," says Viktor Ivanov, the head of Russia's Drug Control Agency. "It's pretty obvious that it's not because everyone has suddenly developed headaches."
Heroin addiction kills 30,000 people per year in Russia – a third of global deaths from the drug – but now there is the added problem of krokodil. Mr Ivanov recalled a recent visit to a drug-treatment centre in Western Siberia. "They told me that two years ago almost all their drug users used heroin," said the drugs tsar. "Now, more than half of them are on desomorphine."
He estimates that overall, around 5 per cent of Russian drug users are on krokodil and other home-made drugs, which works out at about 100,000 people. It's a huge, hidden epidemic – worse in the really isolated parts of Russia where supplies of heroin are patchy – but palpable even in cities such as Tver.
There are some easily googleable images of the longterm effects of Krokodil, some of them look fake but they are all incredibly disturbing.