Alcohol

Ethanol

C2H5OH.

The alcohol in alcoholic drinks

Most common toxic substance detected in toxicology

Methanol

Extremely toxic solvent metabolised to formic acid.

Found in antifreeze, windscreen wash, paint thinners

Formic acid lowers blood PH causing too much acid in bodily fluids which can be fatal

Formic acid binds to retinas causing blindness

Isopropanol

Common industrial solvent, less toxic than methanol.

Metabolised to acetone

More severe CNS depression than ethanol

intoxication, coma, respiratory depression

Ethylene Glycol

Toxic,

Found in antifreeze

metabolised to oxalic acid, reacting with calcium in the body to form calcium oxalate leading to kidney failure which can cause multi-organ failure and death

Chloral Hydrate

Prodrug converted to trichloroethanol in the body.

Prodrug = something administered in an inactive form - converted into an active form by metabolic processes

Prescribed driving limits

DUI - offence to be in charge of a moving vehicle after consuming over teh prescribed limit

Breath: 35ug/100

blood: 80ug/100ml

urine: 107ug/100ml

Absorption of ethanol

Taken orally, travels through oesophagus to stomach to pyloric sphincter to intestine. Absorbed via passive diffusion from high concentration in tissue (intestine) to blood.

Peak BAC

1hr after a single dose consumed on an empty stomach

30 mins after the last drink of multiple consumed

What affects absorption of alcohol

Food eaten - slows stomach emptying, less absorption of alcohol

carbonation - increase stomach pressure, pushing alcohol to bloodstream

Body size - smaller individuals with less water - less distribution - higher BAC - more affects

Gender - females have less body water than men - less distribution - higher BAC - more affects

Diffusion

Movement from high to low concentration areas.

Blood Alcohol Concentration (BAC)

Measure of alcohol in blood, expressed in mg/dL.

ADME

Absorption, Distribution, Metabolism, Excretion processes.

Fatty Beverages

Slow down absorption of alcohol.

Mouth Alcohol Effect

False high readings from residual alcohol in mouth.

Henry's Law

Gas concentration in liquid is directly proportional to its pressure.

Blood/Breath Ratio

Constant ratio for alcohol concentration in blood and breath.

Instantaneous Absorption

Assumption that absorption occurs immediately.

GI Tract

Main site for alcohol absorption in the body.

Alcoholic Strength

Concentration of ethanol in a beverage.

Simultaneous Ingestion of Food

Delays alcohol absorption and peak BAC.

Alcohol Elimination

Process of alcohol being metabolized and removed.

Ethanol to acetylaldehyde to acetate to CO2 and H2O

small amounts excreted unchanged from breath, urine and sweat

ADH

Alcohol dehydrogenase, enzyme facilitating alcohol metabolism.

Many different types - explain people different reactions to alcohol - flushing, bad headaches

Widmark factor

Volume of distribution, 0.68 men, 0.55 women.

Elimination rate

Average rate: 15 mg (men), 18 mg (women) per hour.

Tolerance

Adaptation to alcohol effects, varies by individual.

GC-FID

Gas Chromatography with Flame Ionization Detection.

Headspace analysis

Technique for measuring volatile compounds in samples.

Vitreous humor

Fluid in the eye, useful for toxicology analysis, mirrors blood concentrations, less affected by redistribution.

Evidence handling

EtOH will evaporate, be consumed by microbes, be produced PM from glucose

Vitreous humour and urine to determine PM creation.

Preservation of samples to prevent degradation.

Preservative - sodium fluoride

Anticoagulant - potassium oxalate or EDTA

freeze

Gastric diffusion

Movement of alcohol from stomach to bloodstream.

CNS effects

Alcohol depresses central nervous system functions.

Low levels - complex brain functions depressed: sedation, poor coordination, confusion

High levels - simpler functions depressed: anxiety, withdrawl, decrease in feeling

CNS can become so depressed it leads to death

GI tract effects

High alcohol concentrations damage mucosal membranes.

Diuretic effect

Increased urine production due to alcohol consumption.

Liver damage

Long-term alcohol use leads to irreversible liver changes.

Cirrhosis

Severe liver scarring from chronic alcohol abuse.

Analysing ethanol

Breath: Breathalysers: IR spectophotometry

Blood and Urine: GC-FID and headspace

BAC calculation

a = c x p x r

a = amount of alcohol consumed in g, divide by 0.8 to convert to ml,

c = peak BAC

p body mass in kilograms

r = windmark factor

0.68 for men, 0.55 for women

1 unit of alcohol (g)

8g