Depress the central nervous system by
interfering with the transmission of
neural impulses in the nerve cells
Effects of Depressants
Slow down bodily functions especially
motor activity and mental activity
Low doses
– Feelings of calm and reduced anxiety
– Induced sleep
Large doses
– Loss of consciousness, coma, death
Ethanol is the only common alcohol
that can be consumed. Other
common alcohols such as methanol
and isopropyl are much too toxic
Alcohols are used as antiseptics for
injections and to harden skin
Prolonged consumption of alcohol
leads to both psychological and
physiological dependence
Alcoholism also results in
– Violent antisocial behavior
– Social costs to families
– Safety issues especially road accidents
Alcohol Consumption
Short term effects
– Relaxation, confidence, and increased
– Dialation of blood vessels leads to
feelings of warmth
– Impaired judgment
– Lengthened neural response time
Alcohol consumption
Long term effects of heavy drinking
Cirrhosis of the liver and liver disease
Coronary heart disease
High blood pressure and strokes
Fetal abnormalities and fetal alcohol
Alcohol Withdrawal
Sudden discontinuation of alcohol by
heavy drinkers leads to withdrawal
symptoms including
– Delirium
– Tremors’
Synergistic effects of
increased risk of stomach bleeding
with aspirin
increased risk of heavy sedation with
any drug that has a sedative effect on
the central nervous system.
Legal limits for driving
Most states in the US and many
countries have established 0.08%
blood alcohol as the legal limit for
After drinking the concentration of
alcohol in the blood (BAC) increases as
the alcohol is absorbed and then
gradually declines
Alcohol detection
Breathalyser tests
Reduction of potassium dichromate to
Cr3+ ion
Fuel cell where alcohol is oxidized to
produce an electric current
Gas Chromatography
Infrared spectroscopy- intoximeter
Breathalyzer test
involves a redox reaction in which acidified K2Cr2O7
is used as the oxidizing agent. It oxidizes any
alcohol in the breath to ethanoic acid. The orange
Cr(VI) is reduced to green Cr(III) with the gain of
three electrons per Cr.
The two half reactions and the overall reaction are:
The redox reaction, involving transfer
of electrons generates, an e.m.f. that
is converted to a signal in the
breathalyzer device to indicate the
BAC in the sample of breath.
Such devices generally suffer from
inaccuracy and unreliability when used
in legal cases. More accurate analysis
is carried out by gas liquid
chromatography (glc) and infra-red
Police use the Intoximeter to confirm a road side
breathalyzer test. This is an IR spectrophotometer
in which the IR radiation is passed through the
breath sample. If alcohol is present, the frequencies
are absorbed by the sample depending on the
bands present (such as C–H and O–H) and the rest
of the radiation is transmitted.
The recorder then produces the IR spectrum as %
transmittance against wavenumber.
Intoximeter does not distinguish between ethanol
and propanone which is often present in the
breadth of a diabetic patient.
Gas Liquid Chromatography
• unlike the Intoximeter, gas chromatography is able to distinguish
between ethanol and propanone (found in the breadth of diabetics).
Other Depressants
Certain medicines known as
antidepressants are used to treat
anxiety, stress, and clinical depression
These include
– Diazepam (Valium)
– Nitrazepam
– Fluoxetine hydrochloride (Prozac)
Prozac is an example of
the selective serotonin
reuptake inhibitor (SSRI)
SSRIs work by preventing
neurons (nerve cells) from
pulling in the serotonin that
is floating in the space
between neurons. This
allows more serotonin to
build up and improves
communication between
the neurons.
 Prozac® (Fluoxetine hydrochloride)
is an anti-depressant drug that is used to
treat mental depression and is thought to
work by increasing the activity of serotonin,
a neurotransmitter, in the brain.
The chemical structure of Prozac® is unlike
that of Valium® or Mogadon®. Prozac®
contains the amine group which can react
with HCl to produce fluoxetine hydrochloride
which is water soluble.
Valium is a sedative
It is the most prescribed
drug in the world and is
used in the relief of
anxiety and tension.
It is believed to function
by inhibiting nerve
transmission by
interacting with
(Mogadon®, a
common sleeping pill)
is a hypnotic drug
that induces sleep
and it is also used to
control seizures and
infantile spasms.
 Valium® and Mogadon® are
synthetic drugs known as benzodiazepines.
Both have a common structure consisting of
a phenyl (C6H5) group, a fused benzene ring
with a seven membered heterocyclic ring
consisting of two nitrogen atoms, one of
which is a secondary amine.
On the fused benzene ring, valium contains
Cl whereas Mogadon® contains the NO2
• Barbiturates are short acting, and include
pentobarbital, secobarbital, and amobarbital.
• Affect the cortex and create a state similar to
alcoholic intoxication in large doses.
• Extremely dangerous when mixed with alcohol or
other drugs.
• A person in withdrawal suffers anxiety, agitation,
loss of appetite, nausea and vomiting, sweating, a
fast heartbeat, tremors, and cramps. These
symptoms can escalate to convulsions, delirium,
and hallucinations.
How depressants affect