A recent study found states that allowed the use of medicinal marijuana had substantially lower opioid overdose mortality rates compared with states that do not have medical cannabis laws.
In their article examining the association between the presence of state medical cannabis laws and opioid analgesic overdose mortality, titled “Medical Cannabis Laws and Opioid Analgesic Overdose Mortality in the United States, 1999-2010,” published in JAMA Internal Medicine, researchers Bachhuber, Saloner, Cunningham, and Barry wrote “…States with medical cannabis laws had a 24.8% lower mean annual opioid overdose mortality rate (95% CI, −37.5% to −9.5%; P = .003) compared with states without medical cannabis laws.” More interestingly, “…examination of the association between medical cannabis laws and opioid analgesic overdose mortality in each year after implementation of the law showed that such laws were associated with a lower rate of overdose mortality that generally strengthened over time…”
The exact reason for the decrease in opioid overdose mortality due to medical cannabis use is not clear. Beyond their obvious conclusion that the analgesic effect of medical cannabis (any cannabis, really) leads to a dose reduction of the opioid analgesic, their alternative hypothesis that medical cannabis leads to decreased polypharmacy, particularly of benzodiazepines in people taking opioids, making their opioid overdoses potentially less likely to cause respiratory depression and death, is more intriguing.
As far as I know there is no human LD50 for cannabis. Respiratory depression cannot occur with cannabis consumption alone. Beyond negative effects on respiratory tract cilia associated with any smoking, cannabis does not directly antagonize the brainstem respiratory center. Therefore, the combination of cannabis and opioids should empirically be safer than alcohol and opioids, barbiturates and opioids, or benzodiazepines and opioids.
With respect to opioid analgesics, beyond respiratory depression there has been concern about QTc prolongation and sudden cardiac death, particularly with methadone treatment. Could it be that cannabis has positive effects on the cardiac conduction system? Does cannabis “undo” whatever it is that some opioid analgesics do to the heart? If so, what is the mechanism of action? I don’t know, but I have to wonder what cannabis could do physiologically and pharmacologically to change opioid overdose mortality.
This study is retrospective, and has numerous limitations: the analysis cannot adjust for characteristics of individuals within the states with medical cannabis laws, death certificate data may not correctly classify cases of opioid analgesic overdose deaths, and there may be important time- and state-varying confounders that are not included in the model. That said, it blows my mind that using medical cannabis just might be good for someone also using opioid analgesics or might be intrinsically safer than using opioids at all.
There is so much we just don’t know about medical cannabis. Despite calls from the Institute of Medicine years ago to legitimately study the medicinal properties of cannabis, politics continue to cloud reason and the pursuit of science.
Until the late 1930s cannabis was thought to have legitimate medical purpose in the US. After its criminalization, medical cannabis was forgotten for 60 years. Is it time to rethink “Reefer Madness?”
What do you think? Send your comments to Editors@HCPLive.com.
B. Eliot Cole, MD, MPA, is a member of the Pain Management editorial advisory board. He has served in executive positions for several prominent pain management organizations and societies, including the American Society of Pain Educators and the American Academy of Pain Management. He has been a pain management fellow, clinician, educator, and advocate for nearly 30 years and has practiced in a variety of settings serving a wide range of patients.