COLUMBUS, Ohio--Cancer pain patients on opioid therapy who request more medication, or more frequent dosing, are almost always responding to an increase in pain, said Steven Passik, PhD, director, Oncology Symptom Control and Research, Community Cancer Care, Indianapolis.
If their need for medication goes unmet, patients may exhibit drug-seeking behavior. This, in turn, may prompt the patients physicians into mistakenly believing that opioid therapy has turned their patients into drug addicts, he said at a pain seminar sponsored by the Ohio State University Medical Center.
Such an event is extremely unlikely and reflects widespread confusion over distinctions between addiction, tolerance, and physical dependence, Dr. Passik said. One study (the Boston Collaborative Drug Surveillance Project) evaluated 11,882 patients who had no history of drug abuse and found iatrogenic addiction in only 4 patients.
Understanding the Concepts of Tolerance, Physical Dependence, and Addiction
Physicians must understand the concepts of opioid tolerance and physical dependence in order to distinguish them from abuse and addiction, Dr. Steven Passik said in his presentation at the Ohio State University Medical Center.
Tolerance, defined as the need for increasing opioid doses to maintain effects, is rare. "Patients requiring dose escalation most often have an increase in pain," Dr. Passik said.
Physical dependence is a pharmacologic effect characteristic of opioids. Patients who are physically dependent upon opioids will show signs of withdrawal following abrupt dose reduction or the administration of an antagonist. Long-term opioid use for pain can be expected to result in physical dependence.
Addiction, or substance dependence disorder, however, is fundamentally a psychological and behavioral syndrome. Key characteristics include a loss of control over drug use, compulsive drug use, and, especially, continued use despite harm.
Drug-seeking behavior in response to pain is known as pseudoaddiction, a term coined in 1989 by Drs. David Weissman and J. David Haddox, he said. The syndrome resolves when pain medication is increased.
Studies have shown that a significant percentage of physicians fear causing opioid addiction in their patients. Patients, too, fear addiction. Indeed, these concerns are frequently cited as one of several barriers to the adequate treatment of cancer pain.
The fear of addiction is based, not on reality, but on the myths that surround the use of opioids for pain treatment, primarily that such use will lead to drug abuse or addiction, Dr. Passik said. "This is controversial therapy, and there are lots of misunderstandings about it," he commented.
Drug-seeking behavior spans a spectrum of actions. A patient may aggressively complain about the need for more drugs, make unscheduled doctor visits, request a specific drug by name, or even acquire the drug from other medical sources. The patient may occasionally escalate the drug dosage without physician approval. These behaviors, Dr. Passik said, are suggestive of pseudoaddiction.
Behaviors that are more typically associated with addiction, more accurately called substance dependence disorder, include injecting oral formulations, repeatedly escalating drug dosages, or forging prescriptions.
"We need to ask: What is the patient after?" Dr. Passik said. "Pain control? Or a desire for access to drugs to get high or to get rich? Are they self-medicating depression? Anxiety?"
A physician faced with a patient who shows drug-seeking behavior should consider pseudoaddiction as one possible diagnosis. Psychiatric disorder, depression, mild encephalopathy, and anxiety disorder should also be considered, as well as substance dependence disorder and criminal intent.
The diagnosis becomes even more complex when treating patients who are or have been substance abusers. "This is a very hard differential diagnosis in practice," Dr. Passik said. Although the treatment of pain is the same regardless of the patients substance abuse history, the structure of the treatment plan may change, he said. Treatment may require a multidisciplinary team that includes an expert in addiction medicine, for instance.
To better understand pseudoaddic-tion, medical science needs to learn more about the behaviors of various populations undergoing opioid therapy, Dr. Passik said. In a study of cancer patients without a history of substance abuse, he found that 39% had taken unsanctioned doses of opioids when they felt lonely. Another 26% admitted to taking someone elses drugs on occasion.
"We dont really know the clinical significance of any one behavior until we know more about its prevalence in a variety of populations," Dr. Passik said.