Chapter 9: Toxicology

Metabolite

A substance produced by the metabolic break down of a drug in the body.

Idiosyncrasy

An abnormal susceptibility to a drug or other agent that is peculiar to the individual.

Common Drugs of Abuse: Barbiturates

Drug (Test Code): Barbiturates (BAR) Source: Laboratory manufactured Route: Oral, intravenous injection Medical use: depressant, sedative, hypnotic, anticonvulsant Brand names: Seconal, amytal, nembutal Overdose: Respiratory arrest, coma, death

Common Drugs of Abuse: Benzodiazepines

Drug (Test Code): Benzodiazepines (BZO) Source: Laboratory manufactured Route: Oral, injection Medical use: Treatment for anxiety, seizures, sleeplessness, muscle relaxant Brand names: Valium, xanax, restoril, versed Overdose: Coma; can be lethal when combined with alcohol

Opioids

Drugs (such as morphine and methadone) containing or derived from opium, or that have morphinelike effects.

Quantitative Drug Screening

If a quantitative drug screening test is necessary to determine the amount of the drug that is in the patient, a whole blood specimen is collected. The blood specimen is the most common test ordered for medical alcohol tests by law enforcement officials who arrest a person for alcohol intoxication. Legal testing requires strict chain of custody.

Metabolism

The chemical processes that occur within a living organism.

Toxicity

The level at which a drug becomes poisonous in the body.

Pharmacokinetics

The movement of drugs through the body from the time of introduction to elimination.

Cannabinoid

The primary psychoactive compound in marijuana (Cannabis)

Pharmacokinetics

There are five stages of pharmacokinetics: Liberation, Absorption, Distribution, Metabolism, and Elimination

Common Reasons for Performing Drug Screening Tests

1. Determine the cause of bizarre behavior, unconsciousness, or life-threatening symptoms in a emergency situation when an overdose may be possible. 2. Test for drug use in the workplace or in schools, particularly among bus and truck drivers, childcare workers, and public safety workers. These professions generally require a urine or blood drug test as part of the application process and may also require employees to undergo periodic drug testing. 3. To test athletes for drugs that enhance their athletic ability.

Buprenorphine

A Food and Drug Administration - approved drug for treating opioid drug addiction.

Qualitative Drug Screening

A measurement that determines if a substance is present or absent.

Quantitative Drug Screening

A precise measurement of the amount of a substance present in a specimen.

Qualitative Drug Screening

A qualitative drug screening test of the drug is performed to see if the metabolite is present in the same way that the urine dipstick tested for various analytes (Glucose, protein). Urine is the specimen of choice for screening drugs of abuse and is the only testing method approved for federally mandated urine drug testing. Testing of urine detects drugs used in the previous 24-72 hours. Urine samples are also tested to determine if the specimen has been subjected to alteration methods. For example, labs test for Na+, Cl-, creatinine, pH level, and specific gravity (To determine if the individual had water loaded before voiding), oxidant identification, and urine fingerprinting.

Absorption and Distribution

Absorption is the movement of a drug from a body surface, through the tissues and into the blood (called uptake). The blood then carries the drug through the body (Distribution) until it finds its target.

Specimen Collection

Always refer to lab manual for the following: 1. Acute iron poisoning in children who have taken adult iron tablets is a stat test. 2. Chronic exposure to mercury and arsenic poisoning tests. 3. Forensic drug tests for court purposes. 4. Urine screening testing on pregnant mothers for drugs of abuse. 5. Urine and blood drug testing for on the job injuries to rule out an impaired employee.

Common Therapeutic Drugs That are Tested

Amikacin Caffeine Carbamazepine Cyclosporine Digoxin Ethosuximide Gentamicin Lithium Methotrexate Paracetamol Phenobarbital Phenytoin Primidone Salicylic acid Theophylline Tobramycin Valproic Acid Vancomycin

Common Drugs of Abuse: Amphetamine

Drug (Test Code): Amphetamine (AMP) Source: Made in illegal laboratories Route: Smoked, injected, snorted Medical Use: Appetite suppressant, CNS stimulant Brand Names: Adderall, citramine, DexAlone, tanphetamin, zamitam Overdose: Seizures and cardiac arrest

Common Drugs of Abuse: Buprenorphine

Drug (Test Code): Buprenorphine (BUP) Source: Laboratory manufactured Route: Under the tongue injection, skin patch, implant Medical use: Analgesic, treatment for opioid addiction Brand names: Buprenex, suboxone, subutex Overdose: Severe respiratory depression when combined with benzodiazepines

Common Drugs of Abuse: Cocaine

Drug (Test Code): Cocaine (COC) Source: Refined coca bush leaves Route: Nasal, smoked Medical Use: Topical anesthetic, natural stimulant, anesthetic, vasoconstrictor, pain killer, appetite suppressant, altitude sickness Brand Names: Benzocaine, lidocaine, cepacol, dermoplast, lanacane Overdose: Fever, unresponsiveness, difficulty breathing, unconsciousness, stroke, death

Common Drugs of Abuse: Lysergic Acid Diethylamide

Drug (Test Code): Lysergic Acid Diethylamide (LSD) Source: Illicit laboratories, peyote, psilocybin mexicana, fungus on grains Route: Ingested orally Medical use: No medical use Brand Name: None Overdose: Psychosis, flashbacks

Common Drugs of Abuse: Marijuana Hashish or Hash

Drug (Test Code): Marijuana (THC) Hashish or Hash Source: Cannabis sativa, hemp plant, flowers and leaves Route: Smoked, eaten, injected Medical use: Pain relief, glaucoma, appetite stmulant, reduction of nausea from chemo, euphoria, detachment, relaxation Brand Names: Marinol, Dronabinol Overdose: Impaired lung structure, chromosomal mutation, micronucleic white blood cells, cancer, lack of motivation

Common Drugs of Abuse: Methadone

Drug (Test Code): Methadone (MTD) Source: Laboratory manufactured Route: Oral, injected, powder Medical use: Treatment for narcotic addiction, pain Brand names: Methadose, dolophine Overdose: Danger of respiratory and cardiac arrest and death if stopped suddenly

Common Drugs of Abuse: Methamphetamine and Ectasy XTC

Drug (Test Code): Methamphetamine (mAMP) Ectasy XTC (MDMA) Source: Made in illegal laboratories Route: Oral, powder inhalant, crystals smoked Medical use: Nasal decongestant, no medical use Brand Names: Desoxyn Overdose: Seizures, cardiac arrest

Common Drugs of Abuse: Opiates

Drug (Test Code): Opiates (OPI 2000) Source: Poppy refined Route: Nasal, oral, intravenous injection, dermal patch Medical use: Potent pain killer, heroin, morphine, codeine, fentanyl Brand names: Demerol, darvon, vicodin, dilaudid Overdose: Danger of acquired immunodeficiency syndrome (From sharing needles)

Common Drugs of Abuse: Oxycodone

Drug (Test Code): Oxycodone (OXY) Source: Semisynthetic similar to codeine Route: Oral, injection Medical use: Moderate to heavy pain relief Brand names: OxyContin, percodan, percocet Overdose: Death

Common Drugs of Abuse: Phencyclidine

Drug (Test Code): Phencyclidine (PCP) Source: illegal laboratories Route: Oral, intravenous, sniffed, smoked Medical Use: No medical use Brand names: None Overdose: Violence, psychoses, self-injurious behavior, suicide

Common Drugs of Abuse: Tricyclic Antidepressants

Drug (Test Code): Tricyclic Antidepressants (TCAs) Source: Laboratory manufactured Route: Oral, injection Medical use: Treatment for depression, attention deficit hyperactivity disorder, migraines Brand names: Adapin, Norpramin, Anafranil, Pamelor, Tofranil, Eleval Overdose: Panic attacks, hostile or angry feelings, impulsive actions, severe restlessness, very rapid speech

Specimen Collection

Drugs of abuse are generally tested using urine specimens for the qualitative result and urine or blood for the quantitative result. TDM generally uses blood specimens taken in a gold gel tube or a light green heparin tube with gel.

Liberation

Is the release of the active ingredient in a drug from its dosage form. For the active ingredient to be liberated, it must first enter the body by way of solution. The liberation phase extends from the time the drug was administered to the time it dissolves and is able to be absorbed.

Other Toxicology Tests

Other conditions in which a medical Assistant may be asked to collect specimens for toxicology or perform drug screening tests are as follows: Chronic lead poisoning may occur from the lead-based paint found in homes. -K2EDTA tube needed Two tubes offered by BD have been FDA cleared for use in lead testing and are certified to have low lead content, thereby reducing the risk of false-positive lead test results.

Drugs of Abuse

Over the Counter drugs may have toxic effects on the body if taken incorrectly. The MA should record any OTC drugs that are being taken. *Three causes of drug toxicity with OTCs are over dosage, interactions with other drugs, or idiosyncrasy.* -Any drug can be abused, but "Drugs of abuse" are considered to be those illegally obtained for recreational purposes or to satisfy addiction. -Each of the drugs produces a specific metabolite, the substance produced by the metabolism of the drug in the body. The metabolite is then excreted in the urine.

CLIA-Waived Drug Screening Tests

Some offices may perform drug screening tests for companies as part of pre-employment physical examinations or as a requirement for insurance or government mandates. Although plasma samples may be used in drug testing, they are not used as often as urine samples. Blood samples provide information on drugs or alcohol present in the blood at the time of collection and do not measure drug residues that are present as the drug is metabolized. Urine drug testing provides information on drugs taken within 24 to 72 hours. Generally, the instructions require that the operator dip the testing device into the urine and observe the qualitative reactions in a specified time. The results are reported as positive, negative, or inconclusive. CLIA- waived saliva alcohol tests are also available for facilities that screen clients or patients for alcohol. These qualitative tests generally consist of a test strip that turns shades of green or blue if alcohol is present in the subjects saliva.

Drug Half-Life

The amount of time necessary to eliminate 50% of a drug is referred to as its half-life. The half- life cycle varies for each individual depending on sex, age, body weight, and health status.

Metabolism and Elimination

The drug needs to be broken down (Metabolism) into a water-soluble metabolite, which generally occurs in the liver, gut wall, kidney, or skin. After it is broken down, the drug metabolite is eliminated by way of bile from the liver or urine from the kidneys. Drug metabolites may also be excreted through the skin by way of sweat, the lungs by way of expired air, or the salivary or mammary glands.

Most Common Legal Drug

The most common legal drug of abuse in the United States is ethanol, also known as grain alcohol. It is found in beer, wine, and distilled liquors. Ethanol depresses the central nervous system and may lead to coma, progressing to death at the following "Panic" levels: greater than 2000 ug/mL in the blood or greater than 1600 ug/mL in the urine. Alcohol is one of the few drugs that has a direct correlation between blood levels and impaired driving ability. -It is important to note that screening for illicit drugs or alcohol requires the consent of the patient. The patient has the right to refuse. Blood drawn for other tests cannot be used for drug screening or alcohol testing unless the patient gives consent. If a patient is unconscious and unable to give consent, the emergency exception to consent applies.

Absorption

The movement of a substance through a surface of the body into body fluids and tissues.

Overview of Toxicology

The toxicology department in the medical laboratory tests the levels of both therapeutic drugs and drugs of abuse to determine their presence and their harmful or "toxic" effect on the body. They may also test for other poisons, such as lead. Tests are generally performed using blood or urine specimens and sometimes saliva, sweat, or stomach contents. A toxicology test may be used to denote the presence of 1 specific drug or more than 20 drugs. Drugs may be accidentally or deliberately injected, inhaled, swallowed, or absorbed through the skin or mucous membranes.

Distribution

The transport of a drug through the body by the blood.

Therapeutic Drug Monitoring

Therapeutic drug monitoring (TDM) is the process of measuring either the effects of a drug on a patient or the actual levels of a drug being administered to a patient. Most prescribed drugs have a therapeutic range that must be maintained for successful therapy. If a patients drug level falls outside of the range, it may become ineffective if too low or toxic if too high. Therapeutic ranges and the subsequent monitoring of the drug levels in the body give the physician guidelines for prescribing the medication and fine tuning the exact effective amount of medication to keep the patient within the range. *It is very important to collect the blood sample for TDM at a certain time-- either before or after administering the drug.* or the test results will be useless and unreliable.

Liberation

When a prescribed drug has entered the body and has released the active component from its dosage.

Chain of Custody

When testing for drugs of abuse, the MA must ensure that collection of the specimen adheres to the legal "Chain of Custody" guidelines certifying that the collection of the specimen was witnessed and there was no opportunity for the specimen to be tampered with in any way.