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Demand for Codeine Plummets Where Cannabis is Legalized, Study Finds

By Alexander Beadle

Published: Jan 26, 2023   
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States that legalize recreational cannabis use also see a reduction in demand for prescription codeine, according to a new study.

Published in Health Economics, the study examined changes in opioid dispensing across eleven US states that implemented a recreational cannabis law (RCL) between 2010 and 2019. The researchers found a significant reduction in the distribution of codeine to pharmacies in these states after legalization measures came into force.

This is an important finding, the researchers say, as prescription opioid misuse currently contributes to thousands of overdose deaths per year. If recreational cannabis laws cause some of the population to shift away from opioids and towards cannabis, they say, this may have an impact on those overdose cases.

Pharmacies distribute less codeine in states with recreational cannabis

In this new study, researchers used data from the Drug Enforcement Administration’s (DEA) Automation of Reports and Consolidation Orders System (ARCOS), which tracks the flow of controlled substances from their production to their delivery at retail pharmacies, hospitals, specialists, and other locations where controlled substances are distributed.

Specifically, the researchers were interested in shipments of oxycodone, hydrocodone, morphine, and codeine in eleven US states which adopted an RCL between 2010 and 2019. These four opioids collectively make up over 90% of annual opioid distribution, the authors say.

These ARCOS data were also combined with other external datasets to factor in additional information, such as the implementation dates for medical and recreational cannabis laws, Medicaid expansion dates, good Samaritan laws, and data on practicing physician numbers and racial demographics.

The researchers found that the implementation of an RCL resulted in a 26% reduction in the pharmacy-based distribution of codeine. The scale of this reduction was also seen to increase over time – the pharmacy-based distribution of codeine fell by as much as 37% after recreational laws had been in place for four years.

Since the ARCOS data focuses on shipments of drugs, rather than prescriptions data, this allowed for the study to capture potential changes in other ways that prescription opioids are distributed, such as in hospitals or narcotics treatment programs. However, the researchers found no significant changes in opioid distribution at these other facilities. They also found no significant changes in the distribution of the other three opioids studied.

Cannabis legalization may curb opioid misuse

Since the reductions in codeine dispensing were only seen in settings where misuse is possible (pharmacies as opposed to hospitals or specialist clinics), and that only codeine was significantly affected, the researchers believe that RCLs could be reducing instances of opioid misuse.

“This finding is particularly meaningful,” senior author Coleman Drake, an assistant professor at the University of Pittsburgh’s School of Public Health, said in a statement. “Where previous studies have focused on more potent opioids, codeine is a weaker drug with a higher potential for addiction. It indicates people may be obtaining codeine from pharmacies for misuse, and that recreational cannabis laws reduce this illicit demand.”

Given that prescription opioid overdoses led to more than 16,000 deaths in 2020 alone, the researchers say that this unintended consequence of legalizing recreational cannabis could be an important finding from a public health perspective.

“Increasing legal access to cannabis may shift some consumers away from opioids and toward cannabis,” said study author Johanna Catherine Maclean of George Mason University. “While all substances have some risks, cannabis use is arguably less harmful to health than the nonmedical use of prescription opioids.”

“A reduction in the misuse of opioids will save lives,” added lead study author and doctoral candidate Shyam Raman. “Our research indicates that recreational cannabis laws substantially reduce distribution of codeine to pharmacies, an overlooked potential benefit to legalizing recreational cannabis use.”

Cannabis and opioid use

Other studies on recreational cannabis access and opioid use would also support this idea of RCLs tackling misuse. A 2021 study published in the British Medical Journal found that US counties with higher numbers of retail cannabis dispensaries also recorded lower levels of opioid-related deaths. The researchers also noted a strong link between the presence of dispensaries and a reduction in deaths linked to synthetic opioids, such as fentanyl.

Another study, also led by Drake and colleagues at the University of Pittsburgh, found that states that legalize recreational cannabis also experience a short-term dip in opioid-related emergency department visits.

And it’s not just recreational cannabis laws that appear to have an impact on opioid use. A recent survey of over 2,000 medical cannabis patients in Florida revealed that 90% of those who had been taking opioids and other pain medications chose to stop or reduce their use of those drugs once they began using cannabis. A recent study of cancer patients also found that around 40% discontinued their use of other pain relievers, such as opioids, while using medical cannabis.


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