Opiates Drug Information

Classification

Metabolism

Morphine is rapidly absorbed in the body and extensively metabolized by the liver with only a small portion of the dose excreted as unchanged drug. Most of the drug is excreted as morphine-3-glucuronide. Heroin is rapidly metabolized first to 6-monoacetylmorphine (6-MAM), then further to morphine. The urinary excretion profile of heroin is similar to morphine.

Following an oral dose, codeine is also rapidly absorbed and metabolized, principally to codeine-6-glucuronide, with a small amount metabolized to morphine and norcodeine.

Opiates may be detected in urine for 2+ days following ingestion. The interpretation of results for urines positive for opiates merit special consideration. Since codeine is metabolized to morphine, both substances may appear in the urine following codeine ingestion. However, the codeine concentration is generally greater than that of morphine. Street heroin also contains acetylcodeine, which metabolizes to codeine, therefore, both codeine and morphine may be present in the urine of some heroin users, although morphine generally predominates. In cases of low morphine and codeine concentrations in urine, it is not possible to determine whether codeine, morphine, or heroin were ingested. The presence of morphine alone would generally indicate morphine or heroin use. A specific metabolite of heroin, 6-monoacetylmorphine, is also at times detected and would confirm heroin use. Poppy seeds, which have not been effectively washed, contain trace amounts of codeine and morphine. When consumed in sufficient amounts, poppy seeds may produce urines which test positive for opiates.

Abuse

Opioid compounds have effects on the CNS and the bowel. They produce analgesia, respiratory depression, euphoria, mood changes, confusion, and constipation. Tolerance and dependence develop with repeated use, with overdose being characterized by coma, respiratory depression, and pinpoint pupils. Discontinuing use of the drug in a dependent individual will precipitate a withdrawal syndrome. Heroin and morphine are two of the most commonly abused opioid compounds; however codeine, oxycodone and hydrocodone are also extensively abused as they are more readily available.

Laboratory drug testing: Methods of Analysis

Immunoassay methods for opiates such as enzyme immunoassay (EIA) detect codeine and morphine in free and conjugated forms. Other opioids that cross react with the opiate immunoassays at higher concentrations include hydrocodone and hydromorphone. Routine detection of oxycodone or low levels of hydrocodone requires more sensitive and specific immunoassay screens targeted for oxycodone and hydrocodone. Since immunoassays do not distinguish between the various narcotics, a confirmation method is required that can specifically identify these compounds. Methods commonly used include gas chromatography-mass spectrometry (GC-MS) or liquid chromatography-tandem mass spectrometry (LC-MS/MS). These methods determine the total morphine and codeine content in the urine specimens. Since 90% of these compounds are conjugated in the urine, acid or enzyme hydrolysis is required to convert the conjugated form into the free form.