Before we delve into specific issues and concerns in pain management, we should mention some other drugs encountered in patients being screened for DOA. Although pain management usually involves opiates, there are a few other drugs that may be used and could be detected by the toxicology laboratory. These include suboxone (buprenorphine), fentanyl, tramadol, and THC.
Buprenorphine is a semi-synthetic opioid that is commonly used to treat opiate addiction. It is often given as a 2-drug preparation containing buprenorphine plus naloxone. This is sold under the trade name Suboxone. Buprenorphine is a mixed agonist/antagonist at the opiate receptor. Because of this, buprenorphine blocks the activity of other opiates and induces withdrawal in opiate-dependent individuals who are currently physically dependent on another opiate. Buprenorphine or Suboxone is given to patients to help wean them from their opiate dependence. In this way, it is used very much like methadone. Buprenorphine is not detected by routine opiate screens.
Fentanyl is a synthetic opioid that has become popular in recent years. It is commonly prescribed as a transdermal patch. In this formulation, it can provide chronic pain relief. Because it is a patch, oral ingestion is not possible (or at least not palatable), and so abuse is less likely. The important point concerning fentanyl is that it will not be detected by opiate screens since its structure is significantly different from morphine analogs. It is also present in very low concentrations since the dose needed is so low. Specific assays for fentanyl are needed to detect this drug. Immunoassays for fentanyl are available, though mass spectrometry is usually needed for robust detection of this low-concentration drug.
Tramadol is a very weak activator of the opioid receptor. Its main mechanism of action seems to have more to do with serotonin release and the inhibition of norepinephrine reuptake in the brain. However, metabolites of tramadol are more potent agonists of opioid receptors. Tramadol has some abuse potential but is less euphoric than opiates like morphine. Its use in pain management is increasing.
THC: Marijuana is used medically by many patients since many states now have laws that permit recreational use. The action of THC is more akin to that of a relaxant than a true analgesic. Most clinicians who are treating pain will ask their patients not to use THC if they are being prescribed an opiate; the choice is usually to use one or the other but not both. The use of THC in pain management patients is not common. However, finding THC in the urine of patients undergoing pain management is common.
Methadone is a synthetic opioid with a long duration of action. It is used to help wean patients from opiate dependency.
