Comorbid Substance Use Disorders: Primer for Pain Management
The topic of opioid misuse and abuse (and the rising heroin epidemic) has dominated headlines lately, but what does this really mean for chronic pain specialists. How does one balance the needs of the legitimate pain patient, with those of society as a whole?
Recent data suggests that chronic pain and addiction can go hand and hand. But what is the real incidence? A small-scale trial from 2005 (before the current opioid-epidemic) indicated that approximately one-third (32%) of chronic pain patients may have comorbid substance use disorders (SUD’s).1 However, a 2011 review of the literature found that anywhere from 4% [primary care setting] to 48% [AIDS clinic] of patients with chronic pain have a current SUD.2
In addition, among 5,814 patients with chronic pain who were also prescribed chronic opioid therapy, 19.5% had a current SUD diagnosis documented in their medical record.3 The wide range in prevalence rates reflected in these studies makes it difficult to know what the true incidence of SUD is among chronic pain patients.
This is not a purely academic question, however. Patients with SUD’s have been found to be at greater risk for aberrant medication-related behaviors—for example, if prescribed an opioid, there is an increased risk for prescription opioid misuse and abuse.2 Patients with a comorbid SUD (past and present) are also potentially more difficult to treat and are at higher risk for comorbidities (depression, anxiety, sleep disturbances, etc).2
In the American Psychiatric Association’s Diagnostic and Statistical Manual of Mental Disorders (DSM-5), the revised chapter of “Substance-Related and Addictive Disorders” includes substantive changes to the disorders. According to the new definition, a patient is diagnosed with a SUD if he/she exhibits a maladaptive pattern of substance use leading to clinically significant impairment or distress.4 Table 1 lists clinical features designed to help differentiate patients with pain from those who may misuse or abuse opioids.5
In the 2008 Morasco study, the substances most often used included: cannabis (16%), prescription and/or illicit opioids (15%), and stimulants (cocaine 11% and amphetamines 8%). Although legal, alcohol was found to be the most used substance (73%).3 More than half of the U.S. population has been identified as drinkers, designating alcohol the number one used substance in America.6
How Other Mood-Altering Substances Affect Pain
People have used alcohol to relieve pain since ancient times. However, the greatest pain-reducing effects occur when alcohol is consumed at doses exceeding guidelines for moderate daily alcohol use (Table 2).7
Withdrawal from chronic alcohol use often increases pain sensitivity, which could lead to additional drinking to reverse withdrawal-related increases in pain. Prolonged, excessive alcohol exposure can also generate painful, small-fiber peripheral neuropathies. Abrupt withdrawal from chronic alcohol use can lead to seizures and death, so it is recommended that patients be detoxed under physician supervision.7
Using alcohol with other substances to alleviate pain places people at risk for a number of harmful health consequences, including acute liver failure (with acetaminophen), gastric bleeding (with aspirin or non-steroidal anti-inflammatory drugs), and potential overdose (with opiates).7
Another commonly used substance is marijuana, or cannabis. In 2012, cannabis was the most commonly used federally banned drug, with more than 18 million users.6 Marijuana use disorder is now estimated to affect 6.3% of adults at some point in their lives (see Marijuana Use Disorder is Common and Often Untreated).
More recently, the use of cannabis to manage chronic pain has caused national ethical and legal discourse (see Legal Status of Medical Marijuana). Given the interplay of federal and state laws, an individual could be legally using cannabis under state law but still be in violation of federal criminal law. Thus, as a matter of federal law, providers are discouraged from prescribing cannabis or complete state medical marijuana forms.8
When it comes to cannabis, practitioners must exercise caution. Providers should remain aware that there is a distinction between medicinal cannabis and recreational marijuana. Knowing the potential harms of cannabis use and its negative interactive effects with concurrent use of opioids can also help guide practitioners in their clinical decision-making. Research with cannabis does demonstrate its efficacy in treating anorexia, vomiting from cancer chemotherapy, HIV/AIDS, and other debilitating medical disorders. There are also studies that document cannabis’ therapeutic potential in pain management.9
“A strong evidence base supporting the use of cannabis to treat chronic pain, particularly neuropathic pain, already exists in the peer-reviewed literature,” explained Gregory T. Carter, MD, MS.10 “Medical marijuana works very well for patients with fibromyalgia, degenerative arthritis, spinal cord injury, neuromuscular disorders such as amyotrophic lateral sclerosis and multiple sclerosis, among other conditions.”
However, Dr. Carter cautioned that “cannabis is not for everyone. I would not recommend it for patients with a history of psychiatric disorders, such as schizophrenia.” It is clear from the literature that even low doses of tetrahydrocannabinol (THC) may, in susceptible individuals, cause mental status changes, perceptual distortions, and impaired judgment.8 In addition to significant mental status changes,11 marijuana increases driving accidents,12 adds risks in the workplace and other activities of daily living, and leads to possible substance abuse.13
Therefore, many pain practitioners do not recommend its use, especially in patients with a history of SUD. In the event that a drug screen is positive for marijuana or any other illicit/illegal substance, Gerald Arnoff, MD, noted that: “I will not write for a prescription for any controlled substance—meaning that if the patient is receiving an opioid analgesic for pain from another prescriber, a new prescription will not be written.”14
How Opioid Misuse Affects Pain?
The vast majority of people prescribed opioid medications for pain take their medications responsibly and without incidence. That being said, the diversion of prescription opioids for non-medical uses has become a public health crisis.15 In 2012, more than 2 million people used prescription drugs non-medically for the first time in the U.S.6 Among pain patients, opioid misuse is defined as: