Drug Tests Health Article

Definition

Drug tests are analytical procedures that may be performed on blood, urine, or gastric fluid for the purpose of identifying an unknown drug or measuring the concentration of a specific drug.

Purpose

Drug tests are usually performed for three reasons. 1) To identify an abuse drug. The majority of drug abuse involves one or more of the following substances and these comprise a typical drug of abuse panel: amphetamines, cannabinoids, cocaine, ethanol, opiates (morphine and codeine compounds), and phencyclidine (PCP). Over 85% of drug abuse cases involve those drugs or one of the following: barbiturates, benzodiazepines, methadone, propoxyhene, LSD, methaqualone, and anti-depressants. 2) To identify a drug which may have been ingested or administered in a toxic or lethal dose either accidentally or on purpose. In addition to poisons such as pesticides and heavy metals such as arsenic, drugs are often implicated in accidental overdose and suicide situations. The three most commonly encountered drugs seen in overdose situations are ethanol, salicylate (aspirin), and acetaminophen. 3) To determine whether the amount of a drug in the blood is within therapeutic limits. This process, called therapeutic drug monitoring (TDM), is used to insure that the dose and dose interval of the drug are sufficient to maintain a therapeutic blood concentration throughout drug therapy without risk of toxicity. TDM is also performed to verify that a patient is complying with the physician's orders.