ALCOHOL Dr.

Dinesh Fernando

Alcohol – Chemical compounds that have a functional OH gp. Alcohol was distilled in the 10th
century by the Persians (Iran)

Poisoning by alcohol: Ethyl alcohol / Ethanol / C2H5OH

Methyl alcohol / Methanol / CH3OH
Ethyl alcohol is contained (as absolute alcohol) in alcoho1ic beverages.
Methyl alcohol is contained only in the cheap adulterated alcoholic drinks.
Ethyl alcohol is contained in the following proportions in the following alcoholic drinks.

Rum 50-60%
Whisky, Gin, Brandy 40-45%
Fortified Wines, sherry 18-22%
Natural wines and Burgundy 10-l5%  Fermentation of fruits
Ordinary beer (1 can = 150 cl) 2-5%  Fermentation of barley and hops
Arrack 40% (“Proof” = 2 x % /Vol) ∴ Arrack 80 proof
Kassippu 25-40%

Alcohol is manufactured by the fermentation of sugars and their subsequent - distillation in certain
cases. Fermentation alone can give a conc. up to 12 – 14%. There after distillation to ↑ strength.
Formation of other substances which give odour and taste during Fermentation called congeners
sometimes added to give better smell. ∴ Smell(+) ≠ C2H2OH (+)
1 unit of alcohol is 10ml of pure alcohol. (eg 1 can of beer, 70ml of liqueur) 1-3 units/day decreases
mortality (specially IHD, strokes, dementia, DM) If a female drinks more than 4 units or a male
more than 5 units at a time it is called binge drinking (drinking to get drunk)

Absorption of alcohol:

Site Stomach 33 % and small intestines 66% — begins almost immediately upon ingestion.
Rate of absorption : Affected by presence or absence of food in the stomach.
Rapidity of emptying
Post gastrectomy  ↑ rate of absorption.

Delay caused by : 1. Food - most marked in the presence of fat and protein.
2. Concentration of – Neat sprits (40-45% - alcohol) tends to cause
excess mucus and pylorospasm.
The most effective absorption is from drink with an alcoholic strength of 10-30%.

Give rate increased by Carbonic acid in Carbonated drinks.

Time: absorption is usually complete within an hour

Maximum concentration after a single dose is usually reached within 40-60 mts.(Taylor)

Distribution

After absorption the alcohol is distributed and concentrated in the tissues. The tissues take up
alcohol in proportion to their water content. Bone, adipose tissue and keratin retain only a small
proportion of alcohol.
Metabolism

Oxidation: About 90% of the alcohol absorbed is oxidized in the liver, and 10% is excreted
unchanged in the urine and in the breath. It is not stored in the tissue and it
disappears, from the blood at a fairly uniform rate - 10cc. per kg. Body weight
0.l85cc. of the body weight per hour. 15mg. per cent from the blood per hour.

The first step in the process of oxidation is the break down of ethyl alcohol to acetaldehyde by the
enzyme.
Alcohol dehydrogenase (ADH) and the Co.enzyme Nicotinamide dinucleotide (NAD) which acts
as a Hydrogen receptor.
C2 H5 OH + NAD  CH3 CHO + NADH + H+

Acetaldehyde though toxic does not affect the body because it is rapidly oxidized and covered into,
Acetyl co-enzyme = A and acetate which passes from the liver into the blood. Co-enzyme–A

The greater part of the acetate enters the krebs Tricarboxylic Acid Cycle and is broken down
chiefly in the muscles to Carbon-dioxide and water with the release of energy, (7 cals from each
gram of alcohol) whilst the remainder is incorporated in the body as lipids.

Alcohol will replace other substances in energy production and will diminish the breakdown of fats
and carbohydrates without affecting the breakdown of proteins, resulting in serous metabolic
disturbances such as hypoglycaemia which may therefore follow very heavy drinking episodes.

Excretion

Mainly by the kidney, the sweat and the breath. The glomerular filtrate and the plasma
concentration of alcohol will be the same, but due to resorption of water in the tubules, the
concentration in the urine will be more than in the blood, in the ratio 4: 3.

Blood concentration varies according to the stage of absorption i.e. rising during absorption and
decreasing with elimination, and the blood urine ratio is at “equilibrium” only during the middle
period of excretion. The peak urine alcohol concentration usually occurs about 20mts. after the
peak blood alcohol concentration.

If there is urine already in the bladder when the dose of alcohol is taken the concentration in the
urine will not reflect the concentration in the blood for it will be diluted by the urine already
present. Conversely when the level in the blood begins to fall the concentration in the urine ma y be
a ‘false high’ if the bladder still contains urine excreted at a time when the blood concentration was
higher. Therefore, it is important to empty the bladder and wait 15 - 20mts. before collecting
samples for the estimation of alcohol in suspects produced for examination. Problem if patient has
↑ prostate causing incomplete emptying.

A second sample taken 20 minutes later would indicate whether the level was rising or coming
down.

Prof. Dinesh Fernando. Dept. of Forensic Medicine, Faculty of Medicine, Peradeniya

Behaviour

There is a great degree of variability in the behaviour of individuals with the same concentration of
alcohol in the blood, and in the same individual at different times.

Drew and his associates have summarized their findings thus

under 50 mg.% - little change is observed on clinical examination
100 mg.% - a number show mild symptoms a few show decided symptoms

100 mg.% - 200mg.% - The number showing decided symptoms increased and practically all
will be diagnosed as being under the influence of alcohol.
Critical level - l50 mg.% Anyone with a blood alcohol of this level can be considered to have
imbibed a significant amount of alcohol.

Notable alcoholic - 200mg% - 500mg% - marked in co-ordination coma and danger of death

Death can occur at lower levels in chronic lung disease, atherosclerotic heart disease, chronic
disease etc.

Effect of Alcohol: Physiological and psychological effects

USA – 90% of RTA and 50 % of violent deaths related to C2H2OH

From the medico-legal point of view the most important effect is its depression of the CNS.

The first effect is the depression of the highest evolutionary centres i.e. the centres regulating the
conduct, judgment and self criticism then progressively downwards through the centres of earlier
evolutionary origin until the basal emotions are reached and finally the vital centres in the medulla.

1. Feeling of well being and slight excitation of action, speech and emotion are less restrained,
due to a lowering of the inhibition normally exercised by the higher centres. Increased
confidence and carelessness of consequences and there is a lack of self control. The person
becomes his real self i.e. what is underneath comes forward because the restraining
impulses of the higher centres are depressed. He may also become morose, gay, irritable
excitable, sleepy.

2. Sense perceptions and skilled movements are affected.

Threshold to pain is increased.
Less sensitive to variations of light and sound.
Colour vision is affected early.
Can’t register letters or words shown for only a short time. Reaction time to noise and light
is increased.
Visual acuity is reduced and stronger illumination is needed to distinguish clearly, and
dimly lit objects may not be seen at all.

They take longer to see clearly after being dazzled by strong lights (important in night
driving)
They also have a tendency to Tunnel Vision, which can be detrimental when driving.
Clumsiness and in-coordination in the finer and more skilled movements, i.e. in speech and
finger movements.
Nausea and vomiting are common.

3. Motor and sensory cells are deeply affected.

Prof. Dinesh Fernando. Dept. of Forensic Medicine, Faculty of Medicine, Peradeniya

 Speech is thick and slurring
Coordination is markedly affected - patient becomes giddy may stagger and may even fall.

4. Coma with stertorous breathing - due to paralysis of the respirator centres.

5. Death
Recovery (if it takes place) causes the patient to come out of coma, passing into a deep
sleep from which he awakes in about 8 -10 hours and wakes up with nausea and headache.
Coma of more than 5 hours duration is likely to cause death.

Diagnosis of Acute Drunkenness

There is no single test which can determine drunkenness. All the symptoms and signs must be
taken together, with blood and urine analysis before a diagnosis can be made. In the early stages
some one in daily contact, with the subject may be able to detect the signs, but anyone who sees
him/her for the first time would not be able to do so. Special tests for perception, discrimination
and control will give only guidance in arriving at an accurate assessment. In the more advanced
stage: obvious signs may be present.
Face may be flushed.
Pupils - slightly dilated but reactive to light.
Conjunctivae - congested.
Pulse - rapid and of low tension.
Temperature - usually raised on the surface and reduced internally.
Eye - difficulty in fixation, convergence is limited. Nystagmus or diplopia may occur
Speech - indistinct, slurred
Writing - may show loss of coordination.
Memory - for recent events may be diminished. Knowledge of the passage of time is affected early.
Various pathological or physical conditions would give rise to the signs elicited, and these should
be excluded first or the subject may be re-examined a short time later. Blood & Urine tests must be
done to show intoxication by alcohol irrespective of illness or injury.

Drunkenness by itself is not an offence.

The charge would be; drunk & disorderly.
drunk & incapable
drunk in charge of a vehicle

Legal Limits

 30 mg% - Czechoslovakia, Poland, East Europe

 50 mg% - Austria and Scandinavian countries (Mason 323)
 80 mg% - Britain, Canada and few states of USA, Singapore
 100 mg% - Majority of States in USA
 50 mg% - Australia (Mason pg. 5)
 20mg% - Airline pilots

Prof. Dinesh Fernando. Dept. of Forensic Medicine, Faculty of Medicine, Peradeniya

Drunkenness and the Motor Traffic Act

Motor Traffic (amendment) act No. 31 of 1979

An act to amend the Motor Traffic Act.

Section 151 of the Motor Traffic act is amended as follows:

1. No person shall drive a motor vehicle on a highway after he has consumed alcohol or any
drug.
Regulation made by the Minister of Transport under Section 151 and 237 of the Motor Traffic Act
as amended, by act No. 31 of 1979. Motor Traffic (Alcohol and Drugs) Regulations 1979.

No.7, The concentration of alcohol in a person’s blood at or above which a person shall be
deemed to have consumed alcohol, shall be a concentration of 0.08grams of alcohol per 100
ml. of blood. -

According to these regulations the Police Officer is empowered to carry out a breath test and the
driver of the vehicle is required to submit to it. The level of alcohol reflected on the device must be
made known to the suspect.

Doctors legal duties

The doctor called upon to examine a suspect for alcohol must inform him who he is and the reason
for the examination and tell him that the findings may be used in proceedings against him.

Also tell him that he has the right to refuse and then obtain his consent in the presence of witnesses.
Sometimes the suspect refuses consent, then the doctor may persuade him to do so (but no threat or
promise may be given).
If he continues to refuse then no examination can be made but the demeanour and conduct of a
suspected driver could be recorded and this evidence given.
If he is either too drank or unconscious, and cannot consent recorded for examination arrangement
to have him admitted to hospital must be made for immediate medical attention. Consent to
disclose findings to the Police may be obtained when he recovers and is able to do so (In England
the patient may summon a medical practitioner of his own choice to examine him - he himself
paying for the examination).

Presence of Police

Examination must be carried out in privacy, but the police may be close enough to prevent the
suspect from running away.

Purpose

To decide whether the detained person is suffering from Alcoholic Intoxication or from some
pathological condition which may have caused him to be suspected of being under the influence of
alcohol. To assess how much alcohol has been taken and assess it effects on the individuals
behaviour.

The findings are conveyed to the Police and it may later be necessary to submit the facts to court
and be cross questioned. A full medical examination must therefore be made and full notes be kept
of same.
Any abnormalities noted should be recorded.

Prof. Dinesh Fernando. Dept. of Forensic Medicine, Faculty of Medicine, Peradeniya

Pathological states simulating Alcoholic Intoxication

Those may simulate or exaggerate alcoholic intoxication.

1. Severe Head Injuries.
2. Metabolic disorders: Eg. Hypoglycaemia, Diabetic pre-coma Uraemia Hyperthyroidism
3. Neurological conditions associated with dysarthria, ataxia, tremor, drowsiness, Parkinson’s
disease, intra-cranial tumours
4. Effect of a drug - Insulin, barbiturate, Antistamines

5. Pre-existing Psychological disorders – Hypomania, GPI, acute confusion.

6. Pro-dromata of cerebro vascular emergencies which may manifest as confusional states,
amnesia or aphasia.
7. High fever.
8. Exposure to carbon monoxide sufficient to cause significant Anoxaemia (closed vehicle)

Special Susceptibility to alcohol

The detained person may be suffering from a condition in which even a small quantity of alcohol
would impair him seriously.
1. Extreme cold, exposure, fatigue
2. Pre-existing post concussional states (Punch drunk)
3. Chronic cerebro vascular states with a history of cerebral symptoms – severe hypertension
advanced cerebral athero-sclerosis
4. Cerebral depression - caused by drugs such as barbiturates.
5. Neurological conditions.
6. psychological conditions.

Injuries
Serious injury may be visible externally but internal haemorrhage may not be diagnosable
immediately and may cause slowly progressive surgical shock and cause difficulty in diagnosis.
Nervous shock due to an accident - will pass off with time.

Laboratory Investigations
Sample of blood and /or urine to be taken after consent. Sample of the breath for analysis and
estimation of alcohol.

Second Examination
May be requested to enable a suspected diseased state or abnormalities to be confirmed, and to
notice the extent of its influence.

Information to Examinee
The findings should be communicated to the person. In England he may request another
examination by a doctor of his own choice (whose expenses he will have to pay).

Medical Examination - Scheme

Note date and time of commencement and conclusion of the examination. Obtain consent for
examination in writing after informing him of the complications.

Exclusion of Injuries and Pathological States

Appropriate treatment must be given if discovered.

Prof. Dinesh Fernando. Dept. of Forensic Medicine, Faculty of Medicine, Peradeniya

History
Questions that should be asked.
Do you feel well.
When did you last take food and drink (type and quantity)
Are you subject to fits.
Do you suffer from any disease or disability. if so what?
Are you presently under medical treatment. Have you any medicines or drugs with you.
Do you suffer from diabetes. Do you take insulin. What was the time and quantity of the last dose
(or any other hypoglycaemic drug).

General Behaviour
1. General appearance and behaviour.
2. State of dress: Whether soiled by saliva, vomit or due to incontinence.
3. Speech: whether thick slurred or over precise.
4. Self control - whether he can temporarily pull himself together.

Memory and mental alertness:

1. Ask a few questions to test memory
Name, address, occupation
Day of week, Time of day
Recent events.
2. Signature could be compared.
3. Simple sums (depends on the standard of education)

Writing
Copy out a few lines from a book or newspaper.
Note time taken.

Repetition or omission of words or lines

Ability to keep letters in a line.
Ability to read his own writing.
Consider standard of education, retain original and copy.
His own pen or a pencil or ball point pen should be used.
Pulse: Resting pulse at the beginning and end of the examination. In uncomplicated alcoholic
intoxication the pulse is rapid and usually full and bounding.
Temp: Note axillary temperature
Skin: Dry, moist, flushed, pale
Mouth: General state of mouth and tongue.
Tongue - dry/moist, furred, bitten
Presence of artificial teeth absence of large number of teeth
Deformity - cleft palate
Smell of the breath —fresh or stale alcohol. The smell of alcohol may be masked by garlic
peppermints, deodorants betel, cardamom
Eyes: If he wears glasses, allow him to keep them on.
General appearance: lids - swollen or red.
1. Conjunctivae - suffused.
2. Any abnormalities — contact lens artificial eye
3. Colour of the eye (note)

Prof. Dinesh Fernando. Dept. of Forensic Medicine, Faculty of Medicine, Peradeniya

 Visual acuity - Test with charts.
Intrinsic muscle - pupil - appearance.
reaction to light /ordinary light strong torch light
? brisk slow/absent
Extrinsic muscle: Convergance
Strabismus - squint
Nystagmus - fine lateral Nystagmus

Ears : Examine for - gross impairment of hearing

presence of discharge or wax
abnormality of drums

Gait : Ask him to walk across the room (not straight line)

1. Manner of walking - straight, irregular, over precise, staggering reeling or

with feet wide apart.

2. Reaction time - to a direction to turn

Does he turn at once or go a few steps forwards and
then turn

3. Manner of turning - ? 7 Keeps balance

? Lurches forward
? Reels to a side

Stance: Test ability to stand normally.

1. with eyes open
2. with eyes closed.

Muscular, Coordination

1. Place finger to nose

2. Place finger to finger
3. Picking up medium sized object from the floor
4. Lighting a cigarette with a match
5. Unbuttoning and re-buttoning coat

Reflexes : Knee and ankle jerks.

Pulmonary , Cardiovascular and alimentary systems
Heart, lungs, abdomen, must be examined and any disease noted.
BP taken and recorded.

Laboratory investigations: Blood, Urine, breath.

Post-mortem C2H5OH production can cause ↑ of BAC specially in decomposed bodies.

Usually, does not exceed 100 mg% (max 200mg%) vitreous H: can be used as not affected (0.9 of
BAC). (J.For.Sci -1969, 1970). Problem is to find vitreous.

Prof. Dinesh Fernando. Dept. of Forensic Medicine, Faculty of Medicine, Peradeniya

Blood

Special consent must be obtained to take blood from the detained person. The site must be cleaned
with distilled water or saline (spirits or alcohol must not be used). About 5 - 10ml. of blood must
be withdrawn, and placed in a specially prepared glass bottle containing a small quantity of sodium
fluoride. The bottle should be labeled, with Name, Date and Time of Collection and sent to the
sealed, together with a sealed covering letter bearing the specimen of the seal used. (In England -
The sample is divided into two bottles and one is given to the suspect who is free to have it
examined in a lab of his own choice if he so desires). Analysis should be made within four to five
days.

Urine: About 20 ounces of urine should be collected directly into a “clean” collecting bottle and
three samples of about 6 ounces each should be decanted into specially prepared small
bottles (cleaned with hot chromic acid rinsed several times with distilled water and
sterilized).

Preservative used phenyl mercuric nitrate - 0.17g. in 6 ounces bottles. Final concentration
0.1% Each should be stoppered, sealed, labeled - Analyst, Police, Suspect

Breath: The amount of alcohol in 2,100ml. of alveolar air is the same at 37°C as that in l ml. of
blood.

Collection:
Not less than 15 minutes must be allowed to elapse before a specimen is taken. Then any
alcohol in the mouth or behind a dental plate is washed away by the saliva and cannot
interfere with the test.

60-100 ml. (at a single breath) is received into a dry balloon. This specimen of air is than analyzed
to obtain its alcohol content. Analytical apparatus used Breathalyser

Breath tests are being used as a screening test to detect those who should be produced for further
examination.
In this country, at present the results of a breath test are sufficient to charge the driver in court
under the Motor Traffic Act for having a Blood alcohol of over 80mg.% while in charge of a Motor
vehicle on the road.

Post-Mortem appearances

Death following the acute ingestion of alcohol may result from the complications of vomiting -
inhalation of vomitus and bronchopneumonia and respiratory depression. Or a combination of both
(blood alcohol 300 ml /100 ml or higher, smell of alcohol in the stomach contents may be present
but is sometimes obscured.
Stomach contents, blood and urine must be collected for analysis.

The stomach lining is usually hyperaemic and may on occasion show characteristic manifestation
of acute gastritis.
There may be mucosal tears with or without bleeding as result of violent vomiting.

Lungs - evidence of aspiration of food or gastric contents.

Liver - cells may show increased fat content (Following several days excessive drinking).
Brain - may be oedematous.

Prof. Dinesh Fernando. Dept. of Forensic Medicine, Faculty of Medicine, Peradeniya

Methyl alcohol (Methanol)

Methyl alcohol is not produced by fermentation but by distillation. Distillation produces crude
“pyroligenous acid” consisting of Acetic acid, wood alcohol, ethers, ketones etc.
Acetic acid is separated out as a salt. The alcohol is separated by fractional distillation and yields
“denaturing wood alcohol” which is used for the denaturing of ethyl alcohol (methylated spirits’-
90” ethyl alcohol 10% methyl alcohol.

1. Mineralized methylated spirits (CH3 OH + rectified spirits)

2. Industrial methylated spirits
3. Industrial methylatcd spirits (pyridinized)
4. Power methylated spirits

Pure methyl alcohol

Made synthetically or by refining wood I alcohol. It is a colourless fluid with an odour similar to
ethyl alcohol and a burning taste. Does not affect BAC values.

Uses : For denaturing ethyl alcohol, as a solvent for fats and nail varnishes, paints.
For cinematograph films
For the production of formalin and other chemicals and other trade processes - antifreeze in
automobiles (not now)
Also used in the adulteration of alcoholic beverage (Methyl alcohol is cheap because it is
not subject to tax by Govt.)

Fatal dose: 60-250 ml. Blindness may be caused by only 15 ml. Entry is usually by ingestion but
rarely inhalation and skin absorption. in workers. Absorption is quick and action resembles that of
ethyl alcohol. Methyl alcohol is oxidized in the body to formaldehyde and formic acid and these
are toxic. . CH3OH and metabolites have direct toxic effect and cause severe acidosis.
Metabolised 10 times slower than C2H2OH. C2H5OH has 10 times the attimb to alcohol
dehydrogenase, ∴ metabolism of CH3OH is delayed.
Methyl alcohol is also excreted unchanged in the urine

Symptoms

It injested large amount  severe toxicity  coma  death. If small amount ingested the
symptoms are sometimes delayed, several hours or even days sp. If taken with C2H5OH- Headache,
nausea, vomiting, abdominal pain and cramps, drowsy blurred vision altered behaviour.
Marked muscular weakness and depressed cardiac functions (↓HR and ↓BP). Action on the CNS is
more intense and more persistent than with ethyl alcohol. Delirium and coma may occur – lasting
2-3 days. Toxic effects on liver, kidney and highly specialized nerve elements. Severe metabolic
acidosis fairly sudden failure of vision and complete blindness is a known sequel.

Acute poisoning may result from industrial exposure to inhalation of vapours or from absorption
through the skin or from ingestion Metabolism is slow and about a third of the ingested dose may
still be detected after 48 hours. Therefore, damage is continuous. It may take about a week to
eliminate one large dose from the body.

Signs

Odour of C2H5OH, acidotic breathing, engorgement of optic disc, central scotoma, progressive
visual loss, dark urine which is acidotic, convulsion, coma death due to respiratory failure.

Prof. Dinesh Fernando. Dept. of Forensic Medicine, Faculty of Medicine, Peradeniya

Diagnosis

 History
 S&S
 Urine for formic acid
 Blood CH3OH

Treatment
If early gasteric lavage with 5% N.HCO3
Antidote Ethyl alcohol - 50% 0.7m1. per Kg. for 3-4 days to block metabolism of methyl
alcohol.
1.5% NaHCO3 - to counteract thacidosis
Barbitone - may be needed to block delirium
5% Dextrose + Vitamins (Folic acid)
Cover eyes and keep in dark room to prevent optic atrophy

Prognosis - if moderate dose and early treatment  can live but may have blindness or
impairment of insion
- if delay in treatment. or very high dose  death
lethal Dose is > 2 mg / dl (blood level)

Autopsy 1. Well marked cyanosis

2. Odour
3. Small haemorrhages in stomach, serous memebrain and bladder mucosa
4. Gross oedema of brain

Ix – blood and urine for CH3OH, formic acid and formaldehyde. Even traces are
significant as not found normally.

Certification of drivers for consumption of alcohol under the amended Motor Traffic Act and
regulations

As a result of Motor Traffic Amendment Pct No.40 of 1984 in conjunction with motor traffic
(amendment) act No. 31 of 1979 and the regulations made by the Minister of Transport, published
in gazette No. 45 of 13.07.79, the duties of a doctor are as follows:

(1) If a person, said to be a driver of a motor vehicle is produced for examination of

consumption of alcohol or drugs, the doctor should examine such person after obtaining his
consent, preferably in writing.
If consent is refused, the doctor should converse with him and make as many observations
in respect of his behaviour, state of dress, odour of his breath, gait, whether conjunctiva is
suffused or not, colour of the skin of face, whether he is sweating etc. From such
observations it may be possible to issue a report useful to Court pertaining to whether he
had consumed alcohol and was intoxicated.

If consent is obtained, the doctor should examine the person to ascertain whether he has
consumed alcohol or drugs, and if so, whether he is under the influence of same.
If he refuses to submit to examination by a medical officer, the law at present presumes that
such person has consumed alcohol unless evidence to the contrary has been adduced.

Prof. Dinesh Fernando. Dept. of Forensic Medicine, Faculty of Medicine, Peradeniya

 If a blood sample is to be taken by a doctor to examine whether he has consumed alcohol or
drugs, then the purpose for which the blood is being obtained must be clearly explained to
the person concerned. Consent should be obtained in writing stating the purpose as well as
indicating that the results of the examination will be communicated to the Police, Courts or
in the case of an employee, being examined at the request of the employer, to the employer
concerned.

Alan Wayne Jones. Evidence-based survey of the elimination rates of ethanol from blood with applications in forensic
casework. Forensic Science International. 2010;200:1-20

Reliable information about the elimination rate of alcohol (ethanol) from blood is often needed in forensic
science and legal medicine when alcohol-related crimes, such as drunken driving or drug-related sexual
assault are investigated. A blood sample for forensic analysis might not be taken until several hours after an
offence was committed. The courts usually want to know the suspect's blood-alcohol concentration (BAC) at
some earlier time, such as the time of driving. Making these back calculations or retrograde extrapolations of
BAC in criminal cases has many proponents and critics. Ethanol is eliminated from the body mainly by
oxidative metabolism in the liver by Class I isoenzymes of alcohol dehydrogenase (ADH). Ethanol is an
example of a drug for which the Michaelis–Menten pharmacokinetic model applies and the Michaelis
constant (km) for Class I ADH is at a BAC of 2–10 mg/100 mL. This means that the enzyme is saturated with
substrate after the first few drinks and that zero-order kinetics is adequate to describe the declining phase of
the BAC profile in most forensic situations (BAC > 20 mg/100 mL). After drinking on an empty stomach, the
elimination rate of ethanol from blood falls within the range 10–15 mg/100 mL/h. In non-fasted subjects the
rate of elimination tends to be in the range 15–20 mg/100 mL/h. In alcoholics during detoxification, because
activity of microsomal enzyme (CYP2E1) is boosted, the ethanol elimination rate might be 25–
35 mg/100 mL/h. The slope of the BAC declining phase is slightly steeper in women compared with men,
which seems to be related to gender differences in liver weight in relation to lean body mass. The present
evidence-based review suggests that the physiological range of ethanol elimination rates from blood is from
10 to 35 mg/100 mL/h. In moderate drinkers 15 mg/100 mL/h remains a good average value for the
population, whereas in apprehended drivers 19 mg/100 mL/h is more appropriate, since many of these
individuals are binge drinkers or alcoholics. In preparing this article, a large number of peer-reviewed
publications were scrutinized. Only those meeting certain standards in experimental design, dose of alcohol
and blood-sampling protocol were used. The results presented can hopefully serve as best-practice
guidelines when questions arise in criminal and civil litigation about the elimination rate of ethanol from blood
in humans.

Prof. Dinesh Fernando. Dept. of Forensic Medicine, Faculty of Medicine, Peradeniya