Exploring the changing intensity of opioid use

Illegal opioids can create substantial harms, but the extent of those harms depends on multiple factors, including the amount consumed. In a new study, researchers assessed whether opioid consumption intensity varies appreciably over time or context. They found that intensity-as opposed to prevalence-of illegal opioid use varies enormously. These findings have implications for drug treatment and policy.

The study, by researchers at Carnegie Mellon University, RAND, and the University of Maryland, appears in The American Journal of Drug and Alcohol Abuse.

The supply of illegal opioids has grown with the spread of illegally manufactured fentanyl and other synthetic opioids (e.g., nitazenes). Legal supply to individuals who have purchased in illegal markets has also grown with expansions in medications for opioid use disorder and prescribed safer supply (programs that provide prescription pharmaceutical opioids along with supportive services to individuals at high risk of substance use-related harms). Yet despite these changes, there is little systematic monitoring of consumption intensity.

"We wanted to explore whether various populations who use opioids frequently consume roughly the same amounts per day of use, on average, or whether there is appreciable variation from place to place or from time to time," explains Jonathan P. Caulkins, professor of operations research and public policy at Carnegie Mellon's Heinz College, who led the study.

Caulkins and his coauthors searched two global databases (EBSCOhost and PubMed) for literature on different kinds of users: 1) individuals who purchased opioids in illegal markets, 2) individuals who reported pre-existing use upon intake into treatment, and 3) individuals with opioid use disorder who received opioids through the health care system. They identified 135 relevant articles. Based on their analysis, the authors conclude:

• Average consumption intensities vary enormously, from below 100 morphine milligram equivalents (MME) per day for use outside treatment programs where prices are high, to about 600 MME in typical illegal markets, and from 1,100 to 1,800 MME a day when supply is free (e.g., in heroin assisted treatment and injectable hydromorphone treatment).
• Individuals entering treatment report higher consumption intensities than do those not connected to treatment.
• Intensities have tended to be higher recently, while prices have been lower.
• Studies during the fentanyl era are few and difficult to interpret, but suggest that MMEs per day may be much higher than in the past.

Generally speaking, reported average daily consumption tends to be higher for populations with access to cheaper or more abundant supplies. This variation and the adaptability of consumption have several possible implications, the authors say, including:

• Expansions in supply could have greater effects on quantity consumed than is apparent when looking only at data on prevalence.
• Treatment protocols and overdose prevention strategies may need to adjust for higher baseline consumption.
• Assumptions about health harms from long-term use may need to be revisited if they are predicated on lower, historical consumption intensities.

The authors also suggest that epidemiological monitoring programs track average intensities of use, not just numbers of users.

There are at least two ways to improve our understanding of consumption intensities. One is to regularly ask people who use opioids about their consumption and combine this with purity information obtained from law enforcement or drug checking services."

Beau Kilmer, co-Director of RAND's Drug Policy Research Center and study co-author

"Another is to ask people who use opioids about their spending on opioids and combine this with law enforcement data on drug prices, accounting for variation in purity."