Who are the principal prescribers of opioids in the United States?
As a group, primary care physicians are the largest prescribers of opioids ( including both short-acting and long-acting opioid) in the United States. Pain physicians provide less than 6% of short-acting opioids prescriptions, but they are responsible for about 23% of extended-release opioid prescriptions. Orthopedic surgeons write for a significant percentage of short-acting opioids. A mix of other specialists is responsible for the remainder of opioid prescriptions.
The concept of cross-addiction suggests that a person addicted to one reinforcing substance is at a higher risk for addiction to other reinforcing substances. This concept is based on the fact that a person who takes an intoxicant is presumably less able to resist other temptations. The neurobiologic changes that occur with addiction appear to be common amongst most reinforcing substances. Unfortunately, there is little data to confirm the concept other than the high prevalence of polysubstance dependence.
Methadone acts as a mu opioid agonist and an NMDA antagonist. The half-life of methadone ranges from 8 to 90 hours with large inter-individual variation. Onset of analgesia occurs between 10 and 20 minutes after parenteral administration and lasts 4-5 hours. Methadone is 90% protein bound and its inactive metabolites are excreted in the urine and feces. Methadone undergoes metabolism via the cytochrome P450 system (CYP3A4, CYP2B6, and CYP2C19). Drug-drug interactions must be closely monitored.
When handing off opioid prescribing responsibilities to specialty services, what are the ethics and etiquette involved?
Communication between the prescribing physician and specialty service is paramount to a seamless transition. Unless previously coordinated, the prescribing physician should assume prescribing responsibility until the specialty service has completed a full evaluation, including urine toxicology, psychological evaluation, and a comprehensive history and physical. If the prescribing physician is uncomfortable with continued prescribing, a reasonable alternative is weaning the patient off of opioids until the specialty service has completed a full evaluation.
Do cancer patients get addicted to opioids? Do they abuse opioids?
For cancer and non-cancer patients, psychosocial factors play a contributory role in the propensity for the development of addiction and abuse. The prevalence of addiction to opioids in cancer patients varies from 0% -7.7%, while the rate of abuse ranges from 3%-5%.