Student Drinking Behavior at PSU Paper

Lesson 7: Pharmacology of Alcohol

Overview and Objectives

Overview

In this lesson we will discuss the pharmacology of how alcohol works in the body and brain. We will cover the absorption, distribution, metabolism and elimination of alcohol in the body and the acute physical and psychological effects of alcohol consumption.

Objectives

After completing this lesson, students should be able to:

Explain where alcohol comes from and the differences between fermented beverages and liquors. Explain the mechanism of action of alcohol in the brain. Understand the factors which can affect absorption of alcohol into the bloodstream Explain the metabolic process by which alcohol is broken down and the myths regarding alcohol metabolism. Discuss three factors which impact the absorption of alcohol Explain how alcohol is metabolized in the body. Describe how Antabuse works in terms of metabolism. Define a standard drink. Clarify three myths about sobering up. Describe three acute physiological effects of alcohol Explain why you should not allow a friend to “sleep it off.” List the benefits of moderate alcohol consumption Describe three types of tolerances in terms of alcohol use. Introduction

In 2010, The Lancet, the journal of the British medical association, constructed a list of the most addictive and dangerous drugs, based on three criteria:

How likely users were to become addicted to the drug The harm done to the user directly from the drug The harm done to others because of the users drug use. Based on these criteria, the authors rated alcohol as the most harmful drug in the United Kingdom.

When we talk about alcohol, what we’re referring to is ethanol or ethyl alcohol. Ethanol is the result of the fermentation of sugars or starches in grains, fruits, and vegetables.

Beers, wines, malt beverages and ciders are the result of the fermentation process alone and typically have concentrations of alcohol below 12%.

Liqueurs and distilled spirits (rum, vodka, tequila, etc.) are the result of fermentation and they further distillation to remove water from the fermented liquid. These spirits have concentrated

alcohol contents that can range from approximately 10% up to 100% ethyl alcohol. Liqueurs are spirits that have been distilled with added flavorings (peach, vanilla, cinnamon, etc.).

Absorption of Alcohol

How much you feel the effects of the alcohol you drink, and how quickly you feel those effects, depends on how much of the alcohol is absorbed into the bloodstream and how quickly it is absorbed. There are several factors that will influence the absorption of alcohol into the bloodstream. These factors are discussed below.

Gender Differences

Alcohol is absorbed into the bloodstream primarily in the stomach and small intestines. It is metabolized differently in men and women. Men’s stomachs contain small amounts of alcohol dehydrogenase, the enzyme primarily responsible for metabolizing alcohol, so not all the alcohol is absorbed into the bloodstream. Women, however, have lower levels of alcohol dehydrogenase in their stomachs, so very little of the alcohol is metabolized in the stomach. Instead, more of the alcohol that reaches the stomach and small intestines will be absorbed into the blood stream and will need to be metabolized by the liver. This means that the same amount of alcohol will result in a higher proportion of alcohol in the bloodstream for a woman than it would for a man, even if they were the same size. It also means that women are more likely to feel the effects of the alcohol they drink faster than men will, because more of that alcohol goes directly into the bloodstream to begin having an effect on the body and brain.

Aside from gender differences, a few other factors will influence how quickly the alcohol consumed will reach the bloodstream, including the amount of food in the stomach and the characteristics of the drink.

Amount of Food in Stomach

The amount of food in the stomach will change the time it takes for the alcohol consumed to leave the stomach. This is why it is always better to eat before and/or while you are drinking. This will slow the absorption of the alcohol and help keep the concentration of alcohol in your bloodstream at a more constant level.

A number of myths and urban legends exist claiming that certain foods will help prevent you from getting drunk or from having a hangover. Nearly all of these are untrue. For example, bread will not “absorb” the alcohol in your stomach and milk, butter, or oil will not “coat” the lining of your stomach. Although it is true that complex carbohydrates and proteins take longer to digest and will tend to be present in the stomach longer and may help slow the absorption of alcohol over a longer period of time, having any food in your stomach will lessen the effects of alcohol.

Characteristics of the Drink

The characteristics of the drink will also influence the absorption of the alcohol. Drinks containing higher percentages of alcohol will lead to higher concentrations of alcohol in the bloodstream faster because there is more alcohol in the stomach at one time to move into the bloodstream. Carbonation will help the alcohol be absorbed faster than alcohol in non-

carbonated drinks, so the alcohol in champagne will be absorbed faster than the alcohol in non- carbonated white wine.

Alcohol Metabolism

Alcohol is metabolized by alcohol dehydrogenase. As mentioned in the previous section, some of that metabolism happens in the stomach, before the alcohol ever reaches the blood stream (more so for men than women). The rest of the alcohol consumed reaches the bloodstream and is metabolized in the liver by the alcohol dehydrogenase there.

Antabuse (generic name: disulfram) is a drug that is sometimes used to treat severe alcoholism and uses this toxin to form a negative association with drinking. Antabuse blocks the activity of acetaldehyde dehydrogenase so that levels of acetaldehyde build up in the body, causing the drinker to quickly become violently ill. Each time the alcoholic being treated has even the smallest amount of alcohol, their inability to metabolize the acetaldehyde in their system makes them sick. Eventually the alcoholic learns to associate alcohol consumption with being very sick and vomiting and stops drinking.

What Constitutes a "Drink"

Your liver is able to metabolize roughly ½ oz of ethanol per hour. This is equivalent to one standard drink per hour. A standard drink is:

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Myths About Alcohol Metabolism

The rate at which the alcohol consumed is then metabolized is influenced by the health of the liver, the volume of enzymes produced by the liver, and the amount of alcohol to be metabolized at one time. No other external factors will speed up the process and allow you to metabolize more alcohol in a shorter time span, nor are there any successful means of sobering someone up quickly once they have consumed too much alcohol.

There are a number of commonly believed myths, however, about ways to help someone who is intoxicated sober up quickly.

Acute Physiological Effects of Alcohol

Once alcohol enters the bloodstream, it begins to exert effects on the body and brain. Alcohol has several acute (immediate) physical effects on the body. We will look at three here.

Dilation of Peripheral Arteries

Alcohol causes dilation of the peripheral arteries, causing the warm, flushed feeling that people often have when they have been drinking. It is the vasodilation that causes a person’s face to become flushed while they are drinking, too. This flushed, warm feeling often leads people to feel as though alcohol warms them up. The image of St. Bernard rescue dogs carrying small casks of brandy on their collars to warm up avalanche victims persists because of this belief, and many people still carry flasks of whiskey or brandy during cold weather activities, also believing that this will keep them warm.

In reality, drinking alcohol has exactly the opposite effect. Because alcohol causes the blood vessels close to the skin to dilate, it facilitates cooling the body’s temperature (this peripheral vasodilation is the same process that happens during warm weather). The increased blood flow close to the surface of the skin allows heat to radiate out through the skin and the blood to cool. This is why you may feel warmer, but your core body temperature is actually dropping. Additionally, because alcohol inhibits sensory perception in the brain, you may not realize that your body temperature is dropping. This means that if you are drinking and spending time outdoors during cold weather, you increase your risk of developing hypothermia.

Suppression of Vassopressin

Alcohol also suppresses a hormone called vasopressin. Vassopressin is the hormone responsible for helping to regulate blood volume by controlling water content and urine output. It is known as the antidiuretic hormone. By suppressing vasopressin, alcohol acts as a diuretic and increases urine output. Consuming large amounts of alcohol can lead to dehydration, particularly during warm weather, in hot and crowded rooms, or during physical activity (sports, exercise, or dancing). Alcohol’s diuretic effects begin once the alcohol reaches the bloodstream and continues until all of the alcohol consumed is metabolized and eliminated.

The myth about “breaking the seal” is true only in that once you need to go to the bathroom, you have consumed enough alcohol for enough of it to have reached your bloodstream and begin having a diuretic effect. From that point until at least an hour after you stop drinking, you will have alcohol actively working in your bloodstream continuing that effect. Once you stop drinking, it will take at least an hour for the last drink you consume to be metabolized (longer if you have been drinking large amounts of alcohol in a short time frame). For most people, this is the end of their social evening and an hour after that time you are probably home for the night— so it seems as though once you start going to the bathroom, you have to continually go all night.

Irritation of Stomach Lining

Alcohol has one other significant physiological effect in that it irritates the lining of the stomach. This irritation makes the stomach walls more vulnerable to the stomach acid being released to attempt to digest whatever you’ve been drinking. This irritation is partially responsible for the upset stomach and vomiting that often accompanies heavy drinking and hangovers. This irritation is also why alcohol consumption is discouraged for those people who suffer from gastric ulcers or acid reflux.

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Mechanism of Action/Acute Cognitive and Psychological Effects

Alcohol exerts its effects by binding to receptors for GABA. GABA is an inhibitory neurotransmitter that functions similarly to adenosine in that it helps slow down the flow of other neurotransmitters and, thus, lowers activity levels in the brain. When alcohol binds to receptors for GABA, it increases the activity of GABA and by doing so decreases activity levels in the brain. Decreasing activity in various areas of the brain provokes the characteristic effects of alcohol consumption.

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Acute Danger of Heavy Drinking

The danger here is that the alcohol you are consuming in one moment is not immediately available in your blood stream. It takes some time for that alcohol to reach your blood stream and then your brain. The alcohol that may be making you feel sleepy, dizzy, and sick now is alcohol you have already consumed. If someone drinks a lot in a short amount of time, they may pass out or go to sleep with alcohol they have just consumed still entering their blood stream and making its way to their brain. This means that your blood alcohol concentration (BAC) will continue to rise even after you become unconscious. If your BAC rises to a level high enough to begin suppressing life support functioning, that person is in serious danger of dying from alcohol poisoning in their sleep.

NEVER put someone who has been drinking up until they passed out to bed to “sleep it off.” Someone who has been drinking up until they pass out or begin to fall asleep should be awakened and kept awake until they have had time to metabolize most of the alcohol in their bloodstream. If they cannot be kept awake, they should be taken to an emergency room for treatment.

Keeping an individual awake for at least an hour means that all of the alcohol they have consumed has had time to reach their bloodstream and their BAC is unlikely to rise any more from that point.

Benefits of Moderate Alcohol Consumption

Moderate alcohol consumption (an average of approximately 1 standard drink per day) does appear to convey some positive health effects. These positive effects seem to be protective to the cardiovascular system.

Moderate alcohol consumptions is associated with the following:

increased levels of HDLs. decreased levels of LDLs. decreased blood clotting activity. These effects together can help reduce the risk of atherosclerosis or plaque buildup in the arteries.

While alcohol in any drink will produce these effects, they appear to be more pronounced with red wine consumption, possibly because of the other antioxidants in red wine.

Tolerance

We defined tolerance, described the three different types and provided examples in Week 2. Please review this material to refresh your memory. We will now look at tolerance in terms of alcohol use.

Metabolic Tolerance

In metabolic tolerance, your body may build up the enzymes needed to metabolize a drug with continued use. In this case, your body would begin to “stockpile” alcohol dehydrogenase in the liver in order to metabolize the alcohol more quickly when it is present.

Receptor Tolerance

Receptor tolerance means that the receptors in the brain adjust to the presence of the drug in the brain so that the receptors are less sensitive to binding by the drug. In the case of alcohol, receptor tolerance would mean that receptors meant to bind GABA downregulate, or become less available for alcohol binding. This happens in order to protect the receptors from overstimulation and burning out. If fewer receptors are available to bind the drug, the drug will have a diminished effect in the brain.

Behavior Tolerance

Alcohol seems to be particularly associated with behavioral tolerance. Behavioral tolerance is the effect in which you adapt your behaviors, unconsciously, to the presence of a drug under certain conditions.

For example, if you always go to the same bar with the same friends and sit in the same area, you will quickly learn to adapt your behaviors to account for the alcohol you drink under those conditions. This means that you will be able to get up and walk to the bathroom and may not show any signs of impairment because you have adjusted your behaviors to account for the layout of the room, the lighting, the distance, etc. while adapting to the presence of the alcohol in your system. If you decided to go to another bar and had the same amount to drink, you (or your friends) might notice that your behaviors look a lot more like you are intoxicated, even if you haven’t had any more to drink than you normally do. You have lost that behavioral tolerance. Behavioral tolerance is not an adaptation of your body, but rather an unconscious adjustment of behavior to account for the effects of the alcohol.

As was noted in earlier an earlier lesson, behavioral tolerance can occur within a single episode of drinking. Evidence from animal studies suggests that we can unconsciously learn to adapt our behaviors in the period of a few hours to accommodate the effects of alcohol on our behaviors. Again, the danger in the phenomenon is that you may learn to adapt your driving behaviors to account for the presence of alcohol in your system and with the impairment in

areas of the brain responsible for judgment, you may feel as though your driving is not impaired at all. If all goes exactly as it always has while you are driving the familiar route home, you may very well make it without an incident. However, even the smallest deviation from your normal routine—rain, a detour, a bike suddenly crossing your path—and that adaptation will vanish. Because you have not physically adapted to the presence of the alcohol, your reactions and motor coordination are still impaired and you will be unable to react in time to the shift in the environment.

Conclusion

Ethyl alcohol is the drug commonly referred to as simply alcohol and comes from the fermentation of grains or fruits.

Alcohol is a depressant drug that exerts its effects by acting on the GABA system of receptors. By amplifying the effects of GABA, alcohol slows down activity of other neurotransmitters, including those that activate fear, anxiety and embarrassment. This effect is what accounts for many of the behavioral effects we associate with alcohol.

The dose of alcohol consumed is measured by the concentration of alcohol in the bloodstream or BAC. Consumption of alcohol can eventually induce metabolic, receptor, and behavioral tolerance.