- They act on the brain and spinal cord, altering concentration and activity of neurotransmitters. Therefore decreases brain activity and causes a 'depression'.
- Includes tranquilizers, sedatives, hypnotics
- Anti-depressants are used to treat clinical depression
D.4.2 Discuss the social and physiological effects of the use and abuse of ethanol.
- Ethanol is in beer, wine, hand liquor; and is a psychoactive drug
Low doses
- mild excitement, more talkative, confident, relaxed
- beneficial to circulation and diminish cardiovascular diseases because of mild anti-clotting effect.
Use:
- antiseptic properties
- can be used in skin before injection, to clean a small wound
Abuse:
- CNS depressant, therefore change in behaviour, which becomes more adverse/negative as dosage increases
- effects multiply by duration which it occurs
D.4.3 Describe and explain the techniques used for the detection of ethanol in the breath, the blood and urine.
Detection by breath
- Ethanol establishes equilibrium between being dissolved in the blood & released into the air in exhaled breath
- equilibrium constant Kc is fixed at a particular temperature (see Ch.7) so ethanol measured in the breath can be used to assess blood alcohol concentration.
Breathalyzer test
- crystals of potassium dichromate (VI) oxidizes ethanol to ethanal & ethanoic acid. Potassium dichromate (VI) reduced to Cr 3+ ions.
- colour change seen from orange to green, is measured by a photocell and determines concentration but it is not very accurate.
A more accurate process: infrared spectroscopy in an intoximeter
- different molecules absorb different wavelengths of an infrared spectrum, because of different bonds and functional groups.
Ethanol has an absorption band at 2950cm^-1 because of its C-H bond, the O-H bond is also present in water vapour, therefore that bond is not used to detect ethanol.
The size of the peak on the graph indicates the ethanol concentration compared to the ambient air.
** people who have diabetes often have propanone vapour in their breath, therefore it can give a positive result in the infrared rest for ethanol even if they did not consume alcohol.
A fuel cell
- a version of the intoximeter where in the presence of a catalyst, ethanol is oxidised in the air into ethanoic acid then to water and carbon dioxide.
- it converts the energy released in oxidation into detectable electrical voltage that cn be used to measure ethanol very accurately.
Detection by blood and urine
Gas-liquid chromatography- blood/urine vapourised and injected into a stream of inert gas (mobile phase) over the surface of a non-volatile liquid (stationary phase)
- vapour components move at different rates depending on boiling point and relative solubility , therefore each leaves the column after a specific time interval - its retention time
- a peak at the retention time corresponding to ethanol can be used to confirm its presence in the vapour, area under peak = measure of ethanol concentration, then it is compared to a known standard mixture of propan-1-ol, therefore an accurate assessment of ethanol levels.
*****vapourised blood/urine injected into inert gas (e.g. helium) then travels through a heated column, which the tube it's traveled through is coated with a non-volatile liquid, which effectively slows down the movement of the gas. This allows them to emerge from the column at different times. The time between injection and emersion is recorded.*****
D.4.4 Describe the synergistic effects of ethanol with other drugs.
Ethanol -OH group forms a hydrogen bond with water, so it's readily soluble in aq. solution.
Able to dissolve in lipids, therefore enables crossing cell membranes easily.
Ethanol passes from gut into blood, usually through stomach wall then circulates to all the tissue around the body - therefore short time interval between ingestion and effects.
~90% of alcohol is processed through the liver, rest is by lungs and kidneys
Ethanol also passes through the placenta to the fetus when consumed during pregnancy, also passes into breast milk and then to nursing infant.
SYNERGY
- potential to increase activity of other drugs when consumed at the same time.**careful when taken with medication - could lead to fatal results.
Examples of synergy
- with aspirin: increased stomach lining bleeding & risk of ulcers
- with other depressants (e.g. barbiturates/ sleeping pills): heavy sedation, possibly coma
- with tobacco: increase incidence of cancers, esp. in intestines & liver
- with many other drugs: interfere with their metabolism by the liver - possibly greater & more prolonged drug effects.
D.4.5 Identify other commonly used depressants and describe their structures.
Benzodiazepines
- depresses brain emotional activity, therefore are tranquilizers for anxiety disorders & related insomnia.
- commonly used as sleeping pills & muscle relaxants
- relatively few side effects, can cause dependence, therefore mostly used in short-term treatments.
- Includes Diazepam (Valium) & Nitrazepam (Mogadon)
They are non-polar & high in lipid solubility, therefore able to cross the blood-brain barrier
Fluoxetine hydrochloride (Prozac)
- anti-depressant drug: increases levels of serotonin (a neurotransmitter)
- treats depression & eating & panic disorders
- does not depress CNS activity, therefore NOT a depressant.
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