LECTURE 9 Ethanol: Overview and Pharmacokinetics

  • **Introduction to Ethanol
    **

    • Ethanol, commonly known as alcohol or ethyl alcohol, has a simple chemical structure and various applications.
    • Increased demand observed during the pandemic for hand sanitizers, which primarily contain high concentrations of ethanol.

  • Chemical Properties and Uses

    • Ethanol is toxic and can kill cells and bacteria.
    • Various concentrations of ethanol (70%-95%) are used for cleaning, disinfecting, and in wet labs.

  • Fermentation Process

    • Historical context related to the discovery of fermentation which produces ethyl alcohol as a byproduct when yeast digests sugars.
    • Example: Mixing honey with yeast results in fermented honey with alcohol content.
    • Common alcoholic beverages like wine and beer created via fermentation have natural limits due to yeast toxicity from high alcohol concentrations (around 13-14%).

  • Distillation to Increase Alcohol Concentration

    • Distillation developed to extract higher alcohol concentrations beyond fermentation limits.
    • Alcohol vaporizes at a lower temperature than the liquid, collected and re-condensed to obtain distilled spirits (20% - 70% ethanol).
    • Variations in alcoholic beverages (e.g., wine, beer, whiskey) result from different sugar sources (e.g., malt, grapes, corn).

  • Pharmacokinetics of Ethanol

    • Ethanol is highly soluble in water and fat for easy absorption.
    • Absorbed mostly through the upper intestine rather than the stomach.
    • Blood alcohol concentration (BAC) measures alcohol in blood (grams per 100 ml).
    • Legal limits exist for BAC regarding public intoxication and motor vehicle operation.

  • Effects on Thiamine Absorption

    • Alcohol impairs the thiamine transporter in the intestine, leading to vitamin B1 deficiencies, impacting brain function and potentially causing dementia and memory loss.

  • Ethanol Metabolism

    • Initially broken down by alcohol dehydrogenase into acetaldehyde, which is more toxic than alcohol.
    • Acetaldehyde further metabolized to acetic acid and then eliminated as water and carbon dioxide.
    • Breathalyzer tests detect alcohol through exhalation from lungs; metabolism varies among individuals.

  • Tolerance and Genetic Factors

    • Regular alcohol users may develop tolerance due to increased enzyme production for faster metabolism, influenced by genetics impacting aldehyde dehydrogenase production.
    • Variability in how individuals experience alcohol effects based on genetic makeup and enzyme efficiency.

  • Effects of Ethanol on the CNS

    • Acts primarily on GABAergic, glutamatergic, serotonergic, and other systems affecting neurotransmission.
    • GABA A receptors are positively modulated by ethanol, enhancing inhibitory effects in the CNS and thereby depressing overall neural activity.

  • Dopaminergic System Interaction

    • Alcohol consumption increases dopamine release in the nucleus accumbens, potentially driving addiction through rewarding feeling production.

  • Subjective and Objective Effects of Alcohol Use

    • Early intoxication results in mood improvement, reduced anxieties, and socialization but can lead to impaired motor skills, clearer thinking, and increased urge for alcohol use.
    • Higher levels lead to gross motor impairment, blackouts, and eventual loss of consciousness or death due to vital function impairment.

  • Withdrawal and Addiction

    • Two types of alcohol addiction exist: Type One (low genetic risk, high psychosocial risk) and Type Two (high genetic risk).

    • Withdrawal symptoms include seizures and strong cravings; it manifests over stages with increasing intensity following cessation of use (from mild agitation, cravings, nausea to severe hallucinations and disorientation).

  • Hangover Mechanism and Effects

    • Hangovers are complex with causes including acetaldehyde buildup, dehydration, and sleep disruption leading to headaches, nausea, and fatigue.

    • Alcohol's impairing effects on sleep quality can lead to perceived insufficient rest even after a full night of sleep.

  • Conclusion

    • Overall, the effects of ethanol are multifaceted involving chemical properties, metabolic processes, effects on neurotransmission, and complex interactions with various physiological systems.

  • Important to Note: Consideration of alcohol’s detrimental effects, especially regarding chronic use and addiction, is essential in addressing public health issues.