Before we delve into the issues and concerns of 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 (buprenorphrine), 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, which 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. Specific assays for fentanyl are needed to detect this drug. Immunoassays for fentanyl are available.
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 its use in certain circumstances. The action of THC is more of a relaxant than a true analgesic. Most clinicians who are treating pain will ask their patients to not 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.