"Interdiction is critically important to increase the cost and reduce accessibility of opioids," write former Centers for Disease Control chief Thomas R. Frieden and Brandeis University's Andrew Kolodny in a new paper for the Journal of the American Medical Association. "As with tobacco and alcohol, if heroin and illicitly produced synthetic opioids such as fentanyl are more expensive and more difficult to obtain, use should decrease."

But we don't need to extrapolate from alcohol and tobacco policies to figure out what a heroin shortage would do to consumption. The United Kingdom and Australia both experienced heroin droughts in the last decade and a half. It would be wise to look at what happened in those countries before ramping up interdiction efforts in the U.S.

How Heroin Users in the U.K. Responded to the 2010–2011 Heroin Shortage

From October 2010 to January 2011, heroin purity dropped and prices increased across most of Europe, due to a constellation of factors that ranged from fungal infections in Afghanistan's poppy fields to interdiction efforts in Europe. As a result of the reduced supply, heroin prices in the U.K. more than doubled, from £17,000 per kilogram in early 2010 to £40,000 per kilo a year later. At the street level, heroin purity plummeted from around 35 percent pre-drought to 13 percent at the end of the shortage. Basically, wholesale heroin buyers were diluting their product with cutting agents—some of them inert, some of them toxic—in an attempt to maintain their profit margins.

What happened to users? Mandatory drug testing revealed a large drop in positive heroin tests, from 45 percent before the drought to 21 percent in January 2011. While less heroin meant less heroin use, it didn't mean less risky drug consumption. According to surveys conducted by researchers at the London School of Hygiene and Tropical Medicine, many users continued to inject drugs sold as heroin. Several users reported an increase in tissue damage caused by cutting agents, leading to infections and loss of limbs. Others reported severe memory loss lasting several days. Some users realized they weren't buying heroin and adopted "indigenous harm reduction strategies," such as alternating injections with smoking in hopes of reducing the odds of infection.

Other users simply switched to crack cocaine, often in conjunction with depressants, such as benzodiazepines and alcohol. The researchers write that one heroin user "drank 20-30 cans of high strength alcohol beer a day for the duration of the shortage—a practice which he was unable to cease post-drought and subsequently describe[s] as more problematic than his heroin use." The transition to alcohol is particularly noteworthy, considering that intravenous drug users are at higher risk for hepatitis c, which is in turn exacerbated by excessive alcohol consumption.

Many of the heroin users surveyed by the London School researchers were also participating in methadone treatment. As in the U.S., it was not uncommon pre-draught for users to sell their methadone in order to buy heroin. Illicit methadone selling all but disappeared during the drought as users needed the drug to stave off withdrawal symptoms. The U.K.'s experience suggests that reducing heroin and fentanyl importation to the U.S. (a longshot, considering the resources Washington currently expends on such efforts) without an accompanying increase in access to medication-assisted therapy would lead to disastrous unintended consequences. (Frieden and Kolodny, to their credit, call for dramatically expanding access to methadone and buprenorphine for people with opioid use disorders.)

How Heroin Users Reacted to the Australian Heroin Shortage of 2000–2001

Australia's heroin shortage, which began around Christmas in 2000, is probably the most studied drug drought of the last century. As in the U.K., heroin use dropped, but with a slew of adverse consequences that make it difficult to declare it a win for public health.

According to a 2003 report published by the Australian Institute of Criminology and the New South Wales Bureau of Crime Statistics and Research, heroin prices during the shortage increased dramatically for quantities of half a gram and a gram, but only mildly for a quarter gram or less. Users who preferred to purchase quantities of a quarter gram or less told researchers that the drugs were heavily diluted with cutting agents. The Australian government's drug survey confirmed that purity during the drought decreased from approximately 62 to 51 percent. Meanwhile, the price for a single gram of pure heroin increased 112 percent.

At the user level, researchers looked at trends in New South Wales, Australia's most populous state. From July 2000 to June 2001, overdoses plummeted 74 percent in Cabramatta, a suburb of Sydney with the highest rate of heroin use, and 53 percent in New South Wales overall. Drug arrests in Cabramatta declined 64 percent during the drought. Among users who purchased heroin by the gram, median weekly expenditures declined from $550 to $350.

That may sound like a success, but as in the U.K. many users simply found other ways to get high. Of the 56 percent of survey respondents who said they began using other drugs during the heroin shortage, 79 percent substituted cocaine, 33 percent substituted cannabis, 30 percent substituted benzodiazepines, and 17 percent substituted amphetamines. Positive urine tests for cocaine also increased dramatically during this period. Intravenous drug users who began using more cocaine said that they had taken the drug on 90 of the previous 100 days. Prior to the drought, the figure had been 12 days out of 100.

Most troublingly, the Australian drought led to an increase in robberies and other property crimes. Forty-nine percent of respondents told researchers that they had committed crime to support their habits. During the drought, 42 percent said, they committed more crimes to compensate for increased prices. Arrest data confirmed that there were upticks in robbery and in breaking and entering at the height of the drought.

That increase didn't last. The researchers offer several possible explanations for this; the most compelling is that the shift from depressants to stimulants "caused former heroin users to engage in behaviour that brought them to police attention more frequently," and they were quickly arrested and incarcerated. This might also explain why drug possession arrests dropped over the same period even as many heroin users continued buying and consuming illegal substances.

The Australian researchers concluded that demand for heroin is price-elastic, but that isn't necessarily true for America in the era of fentanyl, which is easy to import, harder to interdict, and much more potent in small doses. And it's definitely belied by the number of users who substituted other substances, both in the U.K. and Australia. While substitution may suggest elasticy in heroin prices, the infrequency with which users become completely sober suggests that drug use itself is inelastic. An interdiction strategy that might work for heroin, which comes from only four regions on the planet, won't work for a synthetic drug that can be shipped in small, undetectable packages. And without a nationwide expansion of evidence-based treatment programs, interdiction will do very little to prevent heroin users from substituting with alcohol, which is uniquituous and cheap.