toxicology urine testing for drugs of abuse Flashcards
About drugs of Abuse
- Drugs that are taken for non-medicinal reasons
- Repeatedly and deliberately used in a way other than prescribed or socially sanctioned.
- Usually a single urine specimen is tested for multiple drugs.
- Testing can be requested by governmental, industrial, educational, and sports agencies.
Urine drug testing may be done in the following situations:
- Pre-employment condition
- Testing of current employees in certain circumstances
- Military
- Monitoring of patients in drug rehabilitation programs
- Parolees
- Athletes
- Patient presenting to the ER with an unknown overdose
- Organ transplant candidates
- Pain management clinics
- Psychiatric programs
Drugs of Abuse Limitations
- Only detects recent use
- Does not differentiate casual from chronic use
- Cannot determine:
- Degree of impairment
- Dose of drug taken
- Exact time of use
- Similar drugs may result in a positive test
- Immunoassays are typically used for screening tests
- Specimens above an established cutoff concentration (threshold) are considered presumptively
positive. **** - Specimens below the cutoff are considered negative.
- Positive cases must be confirmed by a more definitive test (GC-MS)- confirmatory method
- Specimens above an established cutoff concentration (threshold) are considered presumptively
Toxicology of drugs of abuse
•Assessment of drugs of abuse is important to:
- Determine the agent responsible for an overdose and provide timely treatment
- Identify drug abuse in non-overdose situations to provide treatment for addiction
•Typically done using a screening test.
- Only detects recent drug use
- Users can avoid detection with short period of abstinence
- A positive result can not differentiate between a single casual use and chronic abuse
- A positive result also does not tell you the time frame the drug was taken or the dosage.
- Screening tests typically use immunoassays
•Gas chromatography/Mass spectrometry is the confirmatory method for most analytes
Urine drugs of abuse test
The following are drugs that are usually tested with urine drugs of abuse cassettes: •Methamphetamines •Cocaine •THC •Methylenedioxymethamphetamine (MDMA) •Methadone •Morphine •Benzodiazepines •Tricyclic Antidepressants (TCAs) •Barbiturates •Phencyclidine (PCP) •Amphetamines •Oxycodone
Positive results can be confirmed by gas chromatography/mass spectrometry (GC/MS)
Drugs of Abuse - Amphetamine and Methamphetamine
- CNS stimulants
- Therapeutic drugs used for:
- Narcolepsy
- Attention Deficit/Hyperactivity Disorders (ADHD)
•High abuse potential
- strong psychological dependence and mild physical dependence
- Tachycardia, increased blood pressure, restlessness, irritability, insomnia, personality changes
- Depression, impaired memory and motor skills - Amphetamine-like compounds are common in allergy and cold medications
- Metabolized in the liver and eliminated unchanged in the urine.
Drugs of Abuse - Amphetamine Analysis
•Immunoassay used as screening test
- Some designer amphetamines may not be picked up (use a more sensitive method)
- Similar drugs may produce a positive result
Ex. Pseudoephedrine (cold medication)
•All presumptive positive results should be confirmed using GC-MS or LC-MS/MS
Drugs of Abuse - Methylenedioxymethamphetamine (MDMA)
•Commonly referred to as ecstasy
- Primarily taken orally
- Less frequently: inhaled, injected or smoked
- Majority is eliminated by hepatic metabolism
- 20% eliminated unchanged in urine
•Half-life of 8-9 hours
•Duration of effects is about 3.5 hours
- Hallucinations, euphoria, empathic and emotional responses, increased visual and tactile sensitivity
Drugs of Abuse - Cannabinoids (THC)
•Group of compounds found in the plant Cannabis sativa
- Used as a medicinal and psychotropic agent
- Euphoria, distorted perceptions, relaxation, and a feeling of well-being
•Psychoactive compounds found in marijuana.
- Most potent and abundant is THC
•THC is lipophilic
•Distributes to highly vascularized tissues within minutes of inhalation of marijuana
•Quickly removed from circulation into brain and fat tissue
•Then redistributes back into blood stream and undergoes hepatic metabolism
- This causes slower elimination*
•THC is metabolized by the liver into several compounds that are then excreted in the urine.
- The major urinary metabolite (THC-COOH) can be detected for up to:
* 5 days - single use
* 4 weeks - chronic, heavy use
•THC-COOH can also be detected in urine as a result of passive inhalation
-Standards have been established for urinary concentrations to differentiate between passive and
direct inhalation
•Analysis:
•Immunoassay
- Use antibody reagent against THC-COOH metabolite
•Chromatographic methods
- GC-MS/MS or LC-MS/MS
Drugs of Abuse - Cocaine (COC)
•Local anesthetic at therapeutic concentrations
- Used in nasal surgery - local anesthesia and vasoconstriction - In ophthalmology - dilate pupils
•One of the most common illicit drugs of abuse
•Potent CNS stimulator at higher concentrations
- Elicits sense of excitement and euphoria
•Frequently taken with ethanol
- 18-25-fold increase in toxicity compared to taking COC alone.
•Taken intravenously present the greatest hazard, followed by smoking
- Product of liver metabolism (benzoylecgonine) can be found in urine up to:
* 3 days - single use
* 20 days - chronic, heavy use - Analysis:
- Immunoassay
- GC-MS or LC-MS for more polar metabolites
Drugs of Abuse - Opiates
- Analgesic, sedative, and anesthetics
- Derived from or related to substances from the opium poppy
- Naturally occurring forms:
- Opium
- Morphine
- Codeine
- Chemically modified forms:
* Heroin
* Oxycodone - Synthetic forms:
- Methadone
* Fentanyl
- Methadone
•High abuse potential
- Physical and psychological dependence with chronic use
•Genetic variation can play a role in metabolism
- Low CYP2D6 activity (poor metabolizers) - may receive inadequate analgesia ( need more to have
same effects)
- High CYP2D6 activity (ultrarapid metabolizers) - risk for adverse responses( need less to have
same effect)
•With acute overdose:
- Respiratory acidosis
- Myoglobinuria
- Increased CK-MB, troponin ( cardiac markers)
•Treatment of overdose - naloxone*****
Drugs of Abuse - Phencyclidine (PCP)
- Illicit drug
- Stimulant, depressant, anesthetic and hallucinogenic properties
•Adverse effects:
- Agitation, hostility, paranoia
•Can produce profound analgesia at anesthetic doses
- awake but incapacitated, with limited voluntary limb movement
•Lipophilic
- Quickly distributes into fat and brain tissue
- Slow elimination
•Can be detected up to 30 days after abstinence in chronic, heavy users
Other Specimens to Detect Drugs of Abuse - Meconium
•First intestinal discharge from newborns
- Begins to form during 2nd trimester and continues to accumulate until birth - Can be used to detect drugs taken by the mother during pregnancy.
•Limitations:
- Low-birth-weight infants may have delayed passage of meconium and could be missed - Sticky material that is hard to work with in the lab
•Can be analyzed using immunoassay and confirmed with LC-MS/MS or GC-MS
•Drugs that are tested for include:
- Cocaine, opiates, cannabinoids, amphetamines, ethanol, PCP
Other Specimens to Detect Drugs of Abuse - Oral Fluid
•Analysis of saliva
Advantages:
•Non-invasive if collection has to be monitored
- Minimizes risk of adulteration
•Fear, anxiety, and discomfort of drawing blood are diminished
Disadvantages:
•Window of detection is short compared to urine
•Metabolites may poorly distribute in fluid
•pH may affect deposition in fluid
•Small volume obtained
•Analysis: GC-MS, LC-MS, LC-MS/MS
Other Specimens to Detect Drugs of Abuse - Hair
- Easily obtained and not easily altered or manipulated
- Long detection window (months to years)
•Sensitive methods of analysis are needed due to relatively low concentrations in hair
- GC-MS - method of choice
•A washing step is usually done to help differentiate between passive exposure (environmental contamination) and active consumption.
