3 forensic toxicology and pharmacology

what is toxicology + forensic toxicology?

the study of poisons + the study of poisons to aid legal investigation

the two types of forensic scientists that work with drugs and poisons are known as what?

toxicologist (look for the presence of drugs/poisons after they are ingested)

seized drug analyst (work with physical evidence, identify illegal drugs)

what does ADME stand for?

• Absorption

• Distribution

• Metabolism

  • drugs are usually metabolized in the liver

• Excretion

these are used to track drugs in the body

• A stimulant that creates a condition characterized by elevations of heart rate, blood pressure, and respiratory rate

  • Provokes intense euphoria

  • Usually sold by prescription/OTC

This drug is known as what?

Amphetamine

effects of cocaine?

a stimulant that resembles amphetamine in terms of effects, but is a natural product

• Extracted from coca leaves using hydrochloric acid

  • Cocaine hydrochloride can be treated with at base and extracted to produce “crack” cocaine

• Mainly metabolizes to methylecgonine in blood

The term often applied to the psychoactive compounds found within marijuana are known as what?

Cannabinoids

what is the major active agent in marijuana and is present in up to 2-6% of weight?

Tetrahydrocannabinol (THC)

• State is characterized by euphoria, altered perception, impaired memory, mood swings, hallucinations/delusions and paranoia with heavy use

The use of multiple drugs, whether prescribed or inappropriate, is known as what?

Polypharmacy

three forms of alchohol + how do they affect the body?

ethanol (beverage alcohol), isopropyl, methanol + they enter the membranes and disrupt the structure of nerve cells → disrupts signaling

what level of concentration of alcohol is consistent with death?

350mg/dL

details about cyanide?

• A toxic substance that is present in many forms of nature

  • Most common is hydrogen cyanide gas

• Death occurs within minutes, and lethal doses are above 2500 ng/mL

• Disrupts the electron transport chain 

what level do your blood carobxyhemoglobin levels need to pass to be at risk of death?

60%

what is the two-phase approach in chemical testing?

screening (presumptive) and confirmatory test

what are immunoassays?

• presumptive tests in which antibodies are enabled to only react when a substance detects them

• Major drawback is not being 100% specific

the means of separating chemicals is known as what?

chromatography

how does TLC (thin-layer chromatography) work?

TLC (a presumptive test) has an organic solvent be spotted onto a glass plate coated with silica (stationary phase), then the plate is placed into a tank with a mobile phase (solvent eg. ethanol) that migrates up the plate

• The more the molecules interact with the silica gel, the slower they move, vice versa

• Smaller molecules move faster, vice versa

what is the most powerful tool for detecting chemical compounds in forensic chemistry? 

gas chromatography, when paired with a detection system

what is gas chromatography also paired with?

mass spectrometry, MS

how does mass spectrometry work?

• In MS, a small amount of the sample must be vaporised

  • MS only requires small samples, which is useful when the amounts of evidence are small

• The vaporised sample is then blasted with a beam of electrons, to knock the electrons off and make positive ions

  • Known as electron impact, the most common form of ionization

• These mass spectrums are then compared with known spectrums to identify the molecule

why is liquid chromotography (LC) paired with multiple mass spectrometers? 

this is known as tandem mass spectrometry, so the results can be as specific and sensitive as possible

what is colourimetric testing?

it uses reagents to cause a chemical reaction which changes colour

• High detection limits; requires a large sample

what is Inductively coupled plasma-mass spectrometry (ICP-MS)?

• The sample is ionized by passing through a 6000 degrees Celsius torch where they are then directed to the mass detector, where ions are separated by mass and charge

• Low detection limits (only need a small sample) but expensive

the term for how a drug/toxin moves through the body is known as what?

pharmacokinetics (aka ADME)

what is toxicogenomics?

it describes how genetic factors can play a role in the toxicity of an ingested drug

two purposes of workplace drug testing?

• Workplace drug testing is done either for hiring purposes or to explain the erratic behaviour of an employee that may have been using drugs

why is postmortem drug testing difficult to do?

the lethal dose for many drugs are not known for obvious reaasons, and Postmortem redistribution (PMR) changes the concentration of drugs in the body after death, as they move from one part of the body to another

what does the Controlled Substances Act (CSA) define?

the possession and usage of drugs

• It recognizes that many of the drugs have legitimate uses, and are classified into different regulated schedules based on the medical use and potential for abuse

what are schedule I drugs?

Schedule I drugs are ones that have a high potential for abuse, with no medical exceptions

• Heroin

• LSD (aka acid and lucy)

• Marijuana

what are schedule II drugs?

Schedule II drugs are ones with high potential for abuse but have accepted medical uses; abuse can lead to severe addiction and dependence

• Morphine

• Cocaine

• Methamphetamine

do schedule III drugs have less potential for abuse and addiction?

yes, examples include anabolic steroids and some codeine and barbiturates

schedule IV and V drugs have decreasing risk and increasing legitimate values. what are some examples?

• Valium (IV)

• Over-the-counter (OTC) cough medicines with codeine (V)

what is SWGDRUG and what do they do?

• Scientific Working Group for the Analysis of Seized Drugs have recommendations that represent accepted analytical standards

• SWGDRUG provides recommendations for the types and minimum number of tests required to identify seized drugs

three categories for analytical techniques for identifying controlled substances?

• Category A, Specific Examinations 

• Category B, Moderately Specific Techniques

• Category C, Nonspecific Techniques

two types of identification for controlled substances?

chemical and botanical examinations

botanical vs chemical examinations?

Botanical examinations identify physical features specific to plants that are considered controlled substances

Chemical examinations use wet chemical or instrumental techniques to identify substances that are legally regulated

• The analytical testing sequence increases with each step

four drugs most common for botanical examination?

marijuana, mushrooms, peyote, opium

• The botanical examiner identifies plants and plant materials, not the specific psychoactive ingredients

two step process for identifying cannabis (aka Cannabis sativa)?

• Establishing the plant/plant material through physical characteristics– macroscopic and microscopic examinations

• Establishing the presence of the plant resin that contains the psychoactive components

*Microscopic examination of marijuana includes the identification of the cystholitic (bear-claw shaped) hairs on the top surface of the leaf

what chemical colour test is used to confirm the prescence of cannabinoids and THC in a sample?

Duquenois-Levine test

what resin is found in marijuana and can be found in oil/cake form that can be smoked?

Hashish

• The US federal law does not distinguish between hashish and marijuana

what is the name for a small mexican cactus that is also known as Lophophora williamsii?

Peyote

• Contains mescaline that produces hallucinogenic effect

what substances found inside mushrooms are the controlled substances?

psilocin and psilocybin

• Another step to detect these is required

• Over a dozen different mushroom species contain these compounds

chemical examinations?

..require identification of specific compounds within mixtures

• Procedure:

  • Screening

  • Extraction

  • Confirmation

• Chemical examinations can be:

  • Wet chemicals – screening/sample methods

    • Called “wet” because the chemical is analysed in the liquid phase

  • Instrumental procedures (tools) – screening methods and confirmatory tests (remember GC-MS)

how do chemical colour tests (chemical examination) work?

• Chemical reactions that provide info based on the structure of the substance being tested

• A small amount of the substance is transferred to a plate, then a reagent is added to observe the colour change

• Results are either positive or negative

  • Multiple tests are done as some substances may not change colour

how do microcrystal tests (chemical examination) work?

• A test sample is dissolved in a solution with a reagent, where crystals will later form due to the reaction

• The crystals formed are then compared to a reference standard for identification

• Fast and simple

what do extractions (chemical examination) do?

they separate the compound of interest from the rest of the sample

• Sometimes a combination of extraction methods are needed

The identification of specific drug compounds is usually done with GC-MS and what other thing?

Infrared (IR) spectroscopy

• This uses the compound’s ability to absorb infrared light (humans sense IR as heat)

• Ideal for solid samples

what are clandestine drug laboratories?

• Forbidden locations that manage controlled substances

• Can range from remote locations to neighbourhoods and from small table-top setups to large labs