A patient being prescribed a narcotic analgesic for pain may have a negative urine drug screen for opiates. Sometimes problems arise when a physician or law enforcement officer takes this as evidence of illegal behavior by the patient.
Possible explanations for a negative urine drug screen for opiates:
(1) drug not detected by analytical system
(2) drug detected, but level below threshold for being called positive
(3) patient not compliant
(4) patient mistaken about drug being taken
(5) patient diverting medication to others
Many laboratories use antibody-based analytical systems for identifying drugs of abuse. The antibodies for opiates work well against some (morphine, heroin, codeine) agents but poorly against others. It is important to understand what agents may not be detected by a particular method, and to use an alternative method if one of these agents is suspected.
For example, the opiate method used for the Beckman-Coulter Synchron system:
(1) detects reliably: morphine, codeine, hydrocodeine, hydrocodone, hydromorphone, levorphanol, morphine-3-glucuronide, norcodeine and oxycordone.
(2) does not detect: meperidine (non-opioid), methadone, nalbuphine, naloxone, naltrexone, normorphine, oxymorphone
One factor affecting how likely a person is to be detected depends on how she or he metabolize the drug. Formation of some metabolites may be detectable, while others may not be. For example, patients who metabolize oxycontin to oxymorphone may have negative urine drug screens.
