ethanol Instructor

Ethanol has been a part of human culture for approximately 5,000 years.
An archaeological site excavated by the Smithsonian Institution revealed a brewery operating 5,000 years ago capable of producing 5,900 gallons of beer, likely used for funeral rites of nobility.
The intriguing question arises regarding human brains' ability to process ethanol, which remains relatively unchanged over evolutionary timescales despite some genetic changes occurring in these 5,000 years.

According to Dudley (2000), the "Drunken Monkey Hypothesis" suggests that approximately 10 million years ago, tree-dwelling primates began to spend more time on the ground, shifting their diets to include overripe fruit that had fallen from trees.
Overripe fruits, due to decomposition, contain ethanol as a result of fermentation.
An enzyme known as ADH4 in primates mutated to metabolize ethanol more effectively, allowing these primates to capitalize on this food source with reduced adverse effects.
Reference: Dudley, Robert (2000). "Evolutionary Origins of Human Alcoholism in Primate Frugivory". Quarterly Review of Biology. 75 (1): 3–15.

Ethanol experiences first pass metabolism, which is the process by which the concentration of a drug is significantly reduced before it reaches systemic circulation.
In men, about 15% of ethanol undergoes first pass metabolism via the enzyme alcohol dehydrogenase in the stomach.
In women, this rate is lower, at approximately 8% first pass metabolism via the same enzyme.

Ethanol crosses cell membranes with ease, displaying an absorption pattern similar to that of water.
Gastric absorption of ethanol is rapid and nearly complete after first pass metabolism, and it also crosses the blood-brain barrier (BBB) readily.

Ethanol is characterized by zero-order pharmacokinetics, meaning it is metabolized at a constant rate that is independent of concentration in the blood plasma.
The metabolic pathway involves:
- Step 1: Ethanol + NAD + alcohol dehydrogenase → Acetaldehyde
- Step 2: Acetaldehyde + aldehyde dehydrogenase → Acetic acid
- Step 3: Acetic acid → ATP + ADP + CO2 + H2O
NAD acts as a co-enzyme, crucial for the conversion of ethanol to acetaldehyde, indicating that the metabolism of ethanol is contingent on NAD levels.
One standard drink contains 14 g of ethanol, and the body can metabolize approximately 170 g within 24 hours.

Antabuse interferes with the alcohol metabolism pathway by blocking aldehyde dehydrogenase, leading to accumulation of acetaldehyde, which causes unpleasant symptoms known as acetaldehyde syndrome.

The metabolic pathway confirms that the final step releases energy in the form of ATP and ADP, hence ethanol contributes calories.
These calories lack nutritional value and excessive consumption can lead to weight gain, while heavy drinkers often exhibit signs of malnutrition despite calorie intake.

Agonism: An agonist is a substance that enhances or increases the effect of another substance.
Antagonism: An antagonist diminishes or reduces the effect of another substance.
Example of agonism: Physostigmine is an acetylcholine agonist that inhibits acetylcholinesterase, preventing acetylcholine breakdown.
Example of antagonism: THC acts as a glutamate antagonist by binding to anandamide receptors, inhibiting glutamate release.

Ethanol consumption is associated with feelings of pleasure due to dopamine (DA) release, which reinforces drinking behavior.
Chronic intake of ethanol may lead to diminished DA synthesis and release, making individuals more prone to seek ethanol to regain lost pleasure from rewards.
The relationship between ethanol and neurotransmitters is complex and includes effects on serotonin (5-HT), opioid systems, and cannabinoid receptors, each contributing to the substance's varying effects.

Ethanol depresses central nervous system (CNS) activity by:
1. Antagonizing glutamate receptors.
2. Agonizing GABA receptors, which enhances inhibitory neurotransmission, leading to sedation.
The development of tolerance often results in increased receptor numbers (upregulation of glutamate and calcium receptors), producing withdrawal symptoms upon cessation.

Ethanol activates the brain's reward pathway via dopamine system stimulation, resulting in reinforcement and cravings when ethanol intake ceases.
Chronic ethanol use leads to a downregulation of DA pathways, thus reducing the pleasurable effects over time.

Ethanol increases consumption when serotonin levels are suppressed; interestingly, treating with SSRIs like fluoxetine has shown to reduce ethanol intake, suggesting a compensatory mechanism involving serotonin.

Ethanol has been shown to stimulate the release of endogenous opioids, enhancing its rewarding effects; blocking opioid receptors (e.g., with naloxone) diminishes ethanol consumption, indicating an opioid-mediated reward pathway.

Chronic use of ethanol alters cannabinoid metabolic processes, activating the reward response via cannabinoid receptors, reinforcing its addictive potential.

Blood Alcohol Concentration (BAC) serves as a measure of alcohol's effects, calculated as follows:
BAC = rac{(grams ext{ of alcohol consumed})}{(bodyweight ext{ in grams} imes r)} imes 100
where r is the gender constant (0.55 for women, 0.68 for men).
The pleasurable effects of alcohol are typically experienced at BACs between 0.03-0.12%.

Tolerance can appear both acutely and chronically. Studies show that chronic exposure can lead to significant increases in BAC without the expected behavioral signs of intoxication.
Maximum pharmacokinetic tolerance may increase metabolism to a capacity of 1.5 drinks per hour without showing clear intoxication signs.

Moral Model: Views alcoholism as a moral failing; alcoholics are responsible and must develop self-control.
Disease Model: Suggests alcoholism is a permanent condition based on pre-existing factors, asserting individuals are not responsible for their behavior.
Behavioral Model: Focuses on immediate consequences of alcohol use influencing consumption patterns; positive immediate effects increase ethanol use, while delayed negative consequences may deter use.

Gender plays a role in drinking behaviors; studies indicate that women experience adverse effects from lower BACs. The shift to non-traditional gender roles influences drinking patterns and align them more closely with men.

Addressing ethanol dependence involves:
1. Managing acute effects.
2. Managing withdrawal symptoms, which may require medications like Valium and Tegretol for anxiety and seizure prevention, respectively.
3. Preventing relapse typically through treatments like Antabuse, naltrexone (which reduces ethanol's rewarding effects), and acamprosate (a GABA agonist that calms hyperexcitability).
4. Treating co-occurring disorders that may exacerbate ethanol dependence.
Acknowledgment of the comorbid nature of alcoholism with other psychological conditions highlights the complexity of treatment and the necessity of dual diagnosis.