Clinical Chemistry Chapter 29

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Clinical ChemistryChapter 29

• Toxicology

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• Introduction
• At the Emergency Room of a local hospital, the
  story goes, the doctors and nurses dont ask
  patients if they have taken any illegal drugs -
  They ask them what illegal drugs they have been
  taking.
• Intentional overdoses of toxic substances are
  tragically common
• In many cases, when emergency personnel find
  people who are unresponsive, it is reasonable to
  question if the unresponsiveness is due to an
  injury, an underlying medical condition or simply
  because they are too drunk or otherwise impaired
  by another (
  usually illegal or abused prescription ) drug.
• While toxicology is a huge field in itself, the
  Clinical Laboratory is routinely involved to
  testing for toxic substances that are commonly
  found in patients being admitted into hospitals.

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Key Terms

• Toxicology
• Poison
• Acetaminophen
• Salicylates
• Ethanol
• Carbon monoxide

• Drugs of abuse
• Amphetamines
• Steroids
• Cannabinoids
• Cocaine
• Opiates
• Phencyclidine
• Benzodiazepine

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• Objectives
• Define the Key Terms
• Match the scientific and street or generic
  names for toxic substances
• Discuss the physiological effects of the toxic
  substances discussed
• Explain the difference between quantitative and
  qualitative testing
• Discuss the collection and processing of blood
  alcohol specimens
• Discuss the common methodologies used in clinical
  laboratory toxicology testing

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• Blood Alcohol
• Physiological effects of alcohol
• Impairment of the Central Nervous System (CNS )
• All alcohols have similar effects
• Disorientation, euphoria, unconsciousness,
  paralysis
• Acute alcohol poisoning from binge drinking can
  result in death
• Chronic alcohol toxicity
• The liver converts alcohols into aldehydes and
  acid products, which are in themselves toxic
• Long term alcohol abuse can result in cirrhosis
  of the liver, a permanent scarring and loss of
  functional hepatic cells
• Liver damage due to alcohol abuse can be
  monitored by liver enzymes such as ALT, GGT, ALK
  PHOS, LDH, SGOT and bilirubin

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• Different types of alcohols
• Ethanol is the alcohol found in alcoholic
  beverages ( grain alcohol )
• Methanol ( wood alcohol ) is extremely toxic
  usually fatal

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• Medical and legal consequences of blood ethanol
  concentrations
• No alcohol consumption 0 - 10 mg/dl
• Little impairment 0 - 80 mg/dl
• Drunk 100 - 150 mg/dl
• Comatose gt 250 mg/dl
• Death gt 400 mg/dl
• Jail ( DUI ) gt 80 mg/dl
• Different states have interpreted the legal blood
  alcohol limit for driving from between 80 and 100
  mg/dl

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Ethanol Methodology
ADH
Ethanol NAD
Acetaldehyde NADH ADH Alcohol
dehydrogenase NAD does not absorb light at 340
nm NADH does absorb light at 340 nm Alcohol
dehydrogenase is relatively specific for ethanol
and not subject to Interference from other
possible, but less commonly ingested
alcohols Collection of blood alcohol specimens
must avoid the use of disinfectants that contain
any alcohols - Labs must keep an alternative
disinfectant for The collection of blood alcohols
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• Salicylate ( Aspirin )
• Wonder drug Analgesic ( pain killer ), anti
  inflammatory and anti pyretic (
  reduces fever )
• Commonly associated with accidental poisoning in
  children and suicide attempts in adults
• Effects of salicylate overdose
• Primary Stimulation of respiration and
  respiratory alkalosis (
  decreased PCO2 and decreased plasma HCO3 )
• Secondary ( 2 5 hours ) Metabolic acidosis
  as salicylic acid accumulates ( decreased HCO3
  and normal PCO2 )
• Concentrations and effects
• Up to 300 ug/ml Therapeutic
• gt 300 ug/ml Hyperventilation and ringing in
  the ears

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• Acetaminophen ( Tylenol )
• Analgesic ( pain killer )
• Commonly associated with overdoses

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Drugs of Abuse

• Amphetamines ( speed )
• Symptoms Well being , restlessness,
  irritability, psychosis, hypertension, cardiac
  arrhythmias, convulsions
• Common component of allergy and cold medications
• Cannabinoids THC ( marijuana )
• Symptoms well being, euphoria
• THC metabolites can have 4 week half -lives
  detectable in urine
• Cocaine ( coke or crack )
• Symptoms Euphoria, excitement, hypertension,
  seizures, arrhythmias
• Metabolites detectable in urine 20 days after
  last use
• Opiates ( Heroin, morphine, percodan, codeine,
  demerol, darvon )
• Symptoms Pain killers, sedatives
• derived from poppy flower
• Phencyclidine ( PCP )
• Symptoms Stimulant, hallucinogenic, agitation,
  hostility, paranoia

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Drugs of Abuse ( cont )

• Barbiturates ( Phenobarbital )
• Symptoms Sedatives , hypnotics
• Benzodiazepines ( Valium )
• Sedatives
• Urine specimens are preferred for testing drugs
  of abuse
• Drugs of abuse are commonly screened for using
  immunoassay techniques
• Positive test results confirmed with
  chromatography techniques

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Top 10
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Toxicology Links
http//www.vh.org/adult/provider/pathology/CLIA/Dr
ugMonitoring/04Screening.html http//www.drugs.in
diana.edu/publications/iprc/factline/alcdoses.html
http//www.ou.edu/oupd/bac.htm http//www.ecure
me.com/emyhealth/data/Aspirin_Overdose.asp