Thanks to Bugsy of Opiophile and Dankycodone of Bluelight for pointing me toward some primary sources!
*This link contains graphic imagery: discretion in clicking is advised.
The former Soviet Republics have seen better days - and even those weren't particularly good. Between the Berlin Wall's collapse and 2001, the average ex-comrade's buying power decreased nearly 25% in Russia, approximately 60% in Georgia, and over 80% in Tajikistan. The social services provided by the Party (such as they were) got swept aside in the new rush to economic freedom: the entrenched culture of corruption and oppression remained firmly in place. A few plutocrats became richer while most of the populace got a whole lot poorer.
Seeking solace or anesthesia, many turned to drugs. Today much of the region is awash in cheap Afghan heroin, imported through Uzbekistan, Kyrgyzstan, Tajikistan and Kazakhstan. But many users who lack the means to support a heroin habit - or who would rather avoid harsh penalties and legal harassment - have discovered new ways to abuse drugs which are readily available at their local pharmacies.
Antidepressants like Prozac and Paxil act as SSRIs, selective serotonin reuptake inhibitors. They interfere with the brain's uptake of serotonin, thereby leaving more available at the synapses to stimulate the receptors. Tianeptine, the active ingredient in the Russian antidepressent Coaxil, has the opposite effect: it encourages uptake and decreases extracellular serotonin levels. Nobody is sure why this also alleviates depression, or indeed, how tianeptine works within the human brain. But some experimentally-minded addicts have discovered that it also has a pronounced effect on the opiate receptors. Users compare intravenous Coaxil to a slightly speedier heroin shot, with a euphoric if somewhat short-lasting rush.
Alas, these effects only appear at a comparatively high dosage. A Coaxil tablet contains 12.5 milligrams of tianeptine: to get high, users shoot dozens of pills. The resulting solution is filled with insoluble particulates. Most Coaxil abusers use large needles to avoid clogging: this causes damage upon the first venipuncture and results in greater quantities of thrombosis-causing gunk pouring into the circulatory system. Abscesses and gangrene* are common: amputations are frequently required.
Other addicts start with codeine tablets, which are widely available in most pharmacies. After crushing the pills, they engage in a multi-step chemical process akin to the making of "bathtub meth." Iodine and red phosphorous are added to solvents in an effort to transform the codeine into desomorphine, a powerful analog 10 times stronger than morphine and 5 times more powerful than heroin.
The end result of this process contains some desomorphine: it also contains codeine and large amounts of iodine, phosphorous, acids and other toxic chemicals. Russians call it "Crocodile" because users soon develop open sores, peeling and ulcers on their skin*. The liquid is highly corrosive and acidic, causing enormous damage to the circulatory system. Excessive iodine poisons the kidneys, thyroid and liver*: excessive phosphorous can cause bone loss and necrosis of the jawbone, known among 19th century matchmakers as "phossy jaw." Intravenous codeine can cause pulmonary edema and histaminic shock. And because desomorphine is a relatively fast-acting opiate, users tend to inject repeatedly, thereby magnifying the consequences of each dose.