The opium den will return.
Scientists have developed a yeast that will convert glucose to opiates. Thanks to a laboratory theft, this yeast will soon be on the market, meaning, functionally, anyone who knows how to home-brew beer will also be able to make their own heroin.
The results will be explosive. The federal government will attempt to ban home-brewing products, but this will prove to be functionally impossible. The same cartels and desperados currently making methamphetamines will take over the heroin trade, pumping out tens of thousands of gallons of pure opiate per week. Addiction rates will skyrocket, and prisons and hospitals will fill with suffering addicts.
Eventually, the only solution will be to legalize the stuff, which will at least guarantee government oversight and the ability to help those in need. But there will be a period of 20 years or more when this country, and the remainder of the world, is ravaged by addiction. At the end of that time, advances in chemistry will create drugs that counteract the addictiveness of opiates; after that, the drug will be treated much the way we now treat alcohol.