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Chapter 13

PHAR 100 Chapter Notes - Chapter 13: Acetaldehyde Dehydrogenase, Blood Alcohol Content, Aldehyde Dehydrogenase


Department
Pharmacology and Toxicology
Course Code
PHAR 100
Professor
Bill Racz
Chapter
13

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Lesson B.8 Alcohol (Ethanol)
Objectives:
- State the properties of ethanol in terms of absorption, distribution and biotransformation
- State the effects of various blood alcohol concentrations on central nervous system functions
- State the proposed mechanism of neuronal inhibition of ethonal
- State the effects of ethanol on the central nervous system, cardiovascular system, GI tract and liver
in terms of short-term and chronic use
- List the effects of ethanol on the developing fetus
- List the effects of ethanol on driving
Ethanol
- One of the three most used non-medical drugs in Canada
- Produces more health problems and deaths than all illicit drugs combined
- Was first used as a sedative hypnotic drug
- Fermented beverages can be traced back to 8000 BC (mead was prepared from honey)
- Ten to 13mL of absolute alcohol is the amount metabolized by the liver each hour
- Ethanol is absorbed rapidly from the stomach and upper small intestine
- Rate is influenced by:
o Stomach-emptying time
o Ethanol concentration in the GI tract
- Ethanol distributes throughout the total body water and readily distributes across the blood-brain
barrier
- Approx. 95% of ethanol in the body is eliminated by biotransformation (liver)
- Approx. 5% is excreted in the breath, urine and sweat
- Conversion:
o Aldehyde dehydrogenase (ADH) converts alcohol to acetaldehyde (ALDH)
o Acetaldehyde dehydrogenase converts acetaldehyde to acetic acid
o Acetic acid is metabolized by the tissue
- Disulfiram and calcium carbimide (drugs to treat alcohol abuse) inhibit aldehyde dehydrogenase
causing acetaldehyde to accumulate causing individuals to feel sick
- Metabolism of alcohol occurs at a constant rate, despite the blood alcohol concentration
- ADH is rate-limiting saturated at 20mg of alcohol per 100 mL of blood
- Body rate of ethanol metabolism is about 120 mg ethanol/kg body weight/hour
o Therefore: a 70kg person metabolizes ethanol at a rate of 8.4g ethanol/hour or 10.6
ethanol/hour
- Few medical uses exist:
o Alcohol sponges are applied topically to treat fever, skin disinfectant, aperitif to improve
appetite and digestion
o Antidote to treat methanol poisoning
o Hand sanitizer
- Adverse effects:
o Ethanol is a central nervous system depressant
o Chronic, high-dose use affects many organ systems including the CNS, cardiovascular
systm, GI tract and liver
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