Let's not make them depressing to learn about!

By: Karen Lazo

What are Depressants?
  • Depressants are drugs (like tranquilizers, sedatives, and hypnotics) that calm and relax (depress) the central nervous system (CNS) by altering the concentration/activity of chemicals called neurotransmitters.
  • Depressants are sometimes described as anti-depressants because they relieve depression.

Examples of Depressants: Tranquilizers, Sedatives, Hypnotics, and Benzodiazepines


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low to moderate
extremely high/lethal
  • calmness
  • relief from anxiety
  • very relaxed muscles
  • slurred speech
  • staggering gait
  • altered perception
  • sleep induced
  • coma/death
  • respiratory depression

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Market Name
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  • Tranquilizers for anxiety disorder treatments
and related insomnia
  • Sleeping pills and muscle relaxants
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  • Benzodiazepines depress activity in the
part of the brain that controls emotion.

  • Danger: Dependence

Another Example: Ethanol

  • Some antiseptic properties
- clean a small wound
- on the skin before an injection
  • Hardens the skin
- rubbed on feet to prevent blisters
  • Alcoholic drinks
  • Low doses
- creates mild excitement
- helps circulation
- reduces cardio-vascular diseases

An obvious ethanol use!
An obvious ethanol use!

Ethanol Abuse
Ethanol structual formula
Ethanol structual formula
Short-term Effects
Long-term Effects
  • loss of self-restraint, balance, and judgment
  • memory, concentration, and insight are impaired
  • violent behavior associated with domestic
abuse and family breakdown
  • dangerous risk-taking behavior leading to many
accidents involving motor vehicles and machinery
  • dehydration caused by increased urine output leading to
'hangover' and loss of productivity
  • at high doses, can cause vomiting, loss of consciousness,
  • dependence/alcoholism, associated with
withdrawal symptoms
  • liver disease, e.g. cirrhosis, liver cancer
  • coronary heart disease
  • high blood pressure
  • fetal alcohol syndrome
  • permanent brain damage

Metabolism of Ethanol
  • So, let's go back to the structure of ethanol, let's especially notice the polar -OH group that lets it form
H-bonds with H2O. Since it's a small organic molecule it can dissolve in lipids and cross cell membranes easily. After
being consumed, ethanol passed from the gut into the blood, through the stomach wall, and then to all the tissues of the
  • 90% of ethanol is broken down in the liver, the rest by the kidneys and lungs.

Ethanol Analyses

  • Breathalyzer Test
The breathalyzer contains crystals of potassium dichromate (VI) which are orange, but are changed to
green chromium (III) ions as they oxidize the ethanol to ethanal and ethanoic acid.


  • Infrared Spectroscopy
Note: Exact wording from the Bubble book!

- The principle here is that different molecules cause different absorption bands in the infrared spectrum, due to
the vibrations of their particular bonds and functional groups.
-The size of the peak can be used to measure ethanol concentration when compared with a reference from the ambient air.

  • Blood and Urine Analysis
Gas-liquid chromatography:
Note- I'm using exact wording from the Bubble book! I can't summarize this that well on my own!
  1. Blood or urine is vaporized and injected into a stream of an inert gas (the mobile phase) over the surface of a
non-volatile liquid (the stationary phase).

2. The components of the vapour, including ethanol gas, will move at different rates due to their boiling points and relative
solubility in the two phases.

3. Each leaves the column holding the liquid phase after a specific time interval (retention time).

*A peak at the retention time of ethanol can confirm its presence in the vapor.
*The area under the peak is a measure of ethanol concentration relative to a known standard in the mixture such as 1-propanol.

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What is it? No, it isn't a type of energy or new strange brand-name by Colgate or something!
Synergy, specifically for ethanol, is the potential to increase the activity of other drugs when taken at the same time.

Ethanol + alcohol (or medications) ---------→ serious/fatal results

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Ethanol + aspirin
---------→ stomach-lining bleeding + increased risk of ulcers
Stomach ulcers- something you really don't want!
Stomach ulcers- something you really don't want!
Ethanol + other depressants ---------→ heavy sedation
---------→ coma (possibly)

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Ethanol + tobacco
---------→ seems to increase the incidence of cancers (esp. intestines and liver)

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Ethanol + many other drugs
---------→ interferes with metabolism through the liver
---------→ greater and more prolonged drug effects

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Any Questions?

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IB Study Guide: Chemistry
3rd Edition Chemistry by: John Green & Sadru Damji
Pearson Baccalaureate HL Chemistry
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