Alcohol-Related Disorders: Epidemiology & Physiology

Alcohol

The active ingredient in beverage alcohol is ethyl alcohol or ethanol. Alcohol's chemical composition is CH3-CH3-OH and C2H5OH. It is produced by the fermentation of fruits or grains. Different compositions or preparations of alcohol have different characteristics, tastes, or flavors. Congeners such as methanol, butanol, aldehydes, phenols, tannins, and metals give different compositions a characteristic taste or flavor. 

Epidemiology of Alcohol-related disorders

• Alcohol use disorder is among the most common psychiatric disorders in the Western world.
• Tobacco is the most abused substance in India.  
• The lifetime prevalence of alcohol use disorder in the male population is 15% or more. 
• While in females, the lifetime prevalence of alcohol use disorder is 10% or more. 
• However, The lifetime prevalence of alcohol use disorder in psychiatric patients is 30%. 
• The highest drinking frequency and quantity usually occur in the late teens to mid-20s and the peak age of onset AUDs is early 20s to 40 years of age. 
• Early onset of AUD is associated with greater severity. There are problems such as conduct disorder, concomitant drug difficulties, and antisocial behavior.
• AUD onset after the age of 40 has less severe social difficulties, more subtle signs and symptoms of AUD, and a greater likelihood of medical problems. 
• According to the National Mental Health Survey 2015-16, the prevalence of alcohol use disorder in India is 4.7%. 

• The prevalence of tobacco use disorder is the highest i.e. 20.9% in India. 
• The prevalence of AUD is more in males than females. The prevalence of AUD in males is 9.1% whereas in females it is 0.5%. 
• According to WHO, alcohol is the 5th leading risk factor for premature death & disability across the world. 
• Alcohol use and alcohol-related disorders are associated with around 25% of all suicides.

Physiology of Alcohol-related disorders

Concentration of Ethyl Alcohol In Various Preparations

• Different preparations of alcohol may have different concentrations of ethanol by volume.
• The concentrations of ethanol by volume are important during the history taking of patients to get an idea about alcohol by volume present in the body and help in management. 
• In standard beer, the concentration of alcohol by volume is 3-4% whereas it is 8-11% in strong beer.
• In wines, the concentration of alcohol by volume is 5-13% while in fortified wines it is 14-20%. 
• In spirits such as whiskey, rum, gin, vodka, brandy, etc, the concentration by volume is 40% and in arrack, it is 33%.   
• 1 standard drink or unit of alcohol corresponds to 10 to 12 grams of ethanol.
• One standard drink is 1 peg i.e. 30ml of spirits.

Absorption of Alcohol

• Most of the alcohol is absorbed in the small intestine. About 10% of alcohol is absorbed from the stomach and the remainder from the small intestine. 
• The most prominent area of the small intestine for the absorption of alcohol is the proximal small intestine. Many vitamins, such as vitamin B, are also absorbed from this site. Hence, the absorption of such vitamins and nutrients is reduced in individuals consuming alcohol. 
• Peak blood alcohol concentration(BAC) usually reaches 30-90 minutes after alcohol consumption.
• It depends on whether alcohol was ingested on an empty stomach or with food. 
• An empty stomach enhances the absorption of alcohol, whereas food delays the absorption.
• Carbonated drinks enhance the absorption of alcohol. 
• The body has protective mechanisms against rapid alcohol intake. When alcohol is increased in the stomach, mucus is secreted, and the pyloric valve closes, preventing the circulation and absorption of alcohol into the small intestine. 
• Nausea and vomiting are experienced by individuals who consume high amounts of alcohol in less time, caused by pylorospasm due to pyloric valve closure.   
• Alcohol uniformly dissolves in the body's water.
• Tissues with a high proportion of water receive a high concentration of alcohol. 

Mellanby Effect of Alcohol

Mellanby effect states that the intoxicating effects of alcohol are more at a given blood alcohol level when BAC is increasing than for the same BAC when blood alcohol level is decreasing. When alcohol is consumed, the blood alcohol level (BAC) rises and reaches its peak, and after stopping alcohol, the blood alcohol level decreases. The blood alcohol concentration at both points A and point B are the same. According to the Mellanby effect, the intoxicating effect at point A will be more than the intoxicating effect at point B. 

Pathological Intoxication by Alcohol

• In pathological intoxication, there is marked behavioral change, usually aggressiveness due to recent ingestion of an amount of alcohol insufficient to induce intoxication in most people. 
• Trauma and encephalitis may be the predisposing factor to pathological intoxication.   
• Pathological intoxication is also described as Mania a potu.
• In 1979, Coid described pathological intoxication as a condition that follows a variable quantity of alcohol, senseless violent behavior followed by prolonged sleep, or total or partial amnesia. 

Reverse Tolerance of Alcohol

• Reverse tolerance states that the intoxicating effects of alcohol are seen progressively with lower amounts. 
• This is seen in chronic patients who consume alcohol for a long time.
• It is believed to be caused due to Decreasing levels of alcohol metabolizing enzymes and leads to progressive liver dysfunction.

Metabolism of Alcohol in the human body

• About 90% of absorbed alcohol is metabolized through oxidation in the liver. The remaining 10% is excreted unchanged by kidneys and lungs through sweat, and broken lining of the esophagus or stomach, especially in men. 
• For an average 70 kg person with average body fat, 1 drink is likely to raise blood alcohol level by 15-20 mg/dl. 
• Roughly the same amount of alcohol is metabolized in 1 hour i.e. 15 mg/dl/hour. The range can vary from 10-34 mg/dl/hr.  
• Alcohol is metabolized in the liver by an enzyme called alcohol dehydrogenase(ADH) which is mostly present in the cytoplasm. 
• ADH converts alcohol into acetaldehyde. 
• At high BAC, it is also broken down by the microsomal ethanol oxidizing system(MEOS) in the liver. MEOS are present in the microsomes of smooth endoplasmic reticulum. 
• ADH is the rate-limiting metabolic step in the metabolism of alcohol.
• It occurs relatively slowly due to livers' need to handle H+ ions through cofactor NAD (nicotinamide adenine dinucleotide) which is relatively in short supply. 
• Acetaldehyde is further metabolized by the enzyme called aldehyde dehydrogenase(ALDH) which is present in both cytoplasm and mitochondria in liver cells. 
• Acetaldehyde is converted to acetic acid and subsequently metabolized to carbon dioxide and water. 
• This conversion is relatively rapid. So low levels of acetaldehyde are present in the body. 
• Low levels of acetaldehyde can be stimulating and reinforcing.
• While high levels can release histamine, catecholamines cause rapid changes in BP with nausea and vomiting. 
• Disulfiram inhibits ALDH and increases acetaldehyde in the body producing unpleasant symptoms.   
• Some studies suggest that women have lower ADH blood content than men. 
• It may account for women's tendency to become more intoxicated than men with some amount of alcohol.  
• Variants of ALDH and ADH are related to higher reactions to alcohol and lower risk for AUDs, especially in the Asian population. 
• Alcohol in the alveolar air is in equilibrium with alcohol in blood passing through the lungs. The same concentration of alcohol is present in the blood which is passing through the lungs and as well as alveolar air.  
• It helps in determining the alcohol levels in breath by breath analyzer.  
• This method gives a good estimate of blood alcohol levels. 
• Various methods, such as a breath analyzer and the Widmark formula, can be used to measure blood alcohol concentration (BAC).
• The Widmark formula depends on the amount of alcohol consumed and the body weight of the person. 

Percentage of Alcohol In Blood

• Alcohol concentrations are expressed in terms of mg/dl or % wt/vol.  
• A blood alcohol concentration of 100 mg/dl is equivalent to 0.1g/dl or 0.1% wt/vol. 
• At 0.05% BAC, thoughts, judgments, and restraints are loosened and disrupted.
• At 0.1% BAC, the voluntary motor actions become clumsy. 
• In some countries, 0.08% is defined as the legal intoxication level, whereas in India it is 0.03%. 
• With 0.2% BAC, the entire brain motor area is depressed, and emotional areas are also affected. 
• The person appears confused and maybe stuporous at 0.3%.
• 0.4-0.5% of BAC may lead to coma. 
• As the percentage of BAC increases, the breathing and heart rate control centers are affected, which ultimately leads to death due to respiratory depression or aspiration of vomitus.
• Alcohol, benzodiazepines, barbiturates, and other related drugs are depressants.
• They produce similar intoxications, potentially lethal in overdose, especially when taken together, have cross-tolerance with other depressants, and can produce physical dependence with similar withdrawal syndromes.

Tolerance of Alcohol

• Tolerance is the ability to tolerate higher doses of substance.
• There are 3 processes of tolerance.
• Behavioral tolerance is when the person learns through practice how to perform tasks effectively while under alcohol.   
• Pharmacokinetic tolerance is the adaptation of alcohol metabolizing systems to remove alcohol from the body rapidly.
• Pharmacodynamic or cellular tolerance is the adaptation of the nervous system so that it can function despite high blood alcohol concentrations by resisting the actions of alcohol on cells.  

Cross tolerance Of Alcohol

• Cross tolerance is once tolerance has developed to one depressant person is likely to show a similar reaction to another drug of that class.
• For example, if a person has developed a tolerance for alcohol and he stops taking alcohol and starts taking a benzodiazepine, he will be also tolerant to benzodiazepines. 
• A higher amount of benzodiazepine will be required to achieve normal effects in a person tolerant to alcohol. 

Also Read: Treatment of Alcohol-Related Disorder

Frequently Asked Questions

Question: Which of the following is a congener that contributes to the characteristic taste or flavor of different alcohol compositions?

A. Ethanol

B. Butanol

C. Methanol

D. Acetone

Answer: B. Butanol

Question: What is the lifetime prevalence of alcohol use disorder in psychiatric patients?

A. 20%

B. 25%

C. 30%

D. 35%

Answer: C. 30% 

Question: In strong beer, what is the approximate concentration of alcohol by volume?

A. 1-2%

B. 3-4%

C. 8-11%

D. 14-20%

Answer: C. 8-11%

Question: Where is the most prominent area in the small intestine for the absorption of alcohol?

A. Distal small intestine

B. Proximal small intestine

C. Ileum

D. Duodenum

Answer: B. Proximal Small Intestines

Question: According to the Mellanby effect, when is the intoxicating effect of alcohol more pronounced?

A. During increasing blood alcohol levels

B. During decreasing blood alcohol levels

C. Constant throughout

D. At peak blood alcohol concentration

Answer: A. During increasing blood alcohol levels

Question: What is described as the predisposing factor to pathological intoxication?

A. Trauma

B. Vitamin deficiency

C. Genetic predisposition

D. Respiratory depression

Answer: A. Trauma

Question: Which enzyme in the liver converts alcohol into acetaldehyde?

A. Alcohol dehydrogenase (ADH)

B. Aldehyde dehydrogenase (ALDH)

C. Microsomal ethanol oxidizing system (MEOS)

D. Pyloric valve

Answer: A. Alcohol Dehydrogenase (ADH)

Question: Which neurotransmitter system is most significantly affected by alcohol, especially the GABA-A receptor?

A. Dopamine

B. Serotonin

C. Glutamate

D. Acetylcholine

Answer: C. Glutamate 

Question: At what Blood Alcohol Concentration (BAC) level do voluntary motor actions become clumsy?

A. 0.05%

B. 0.1%

C. 0.2%

D. 0.3%

Answer: B. 0.1%

Question: What does pharmacodynamic or cellular tolerance involve in the context of alcohol?

A. Adaptation of alcohol metabolizing systems

B. Adaptation of the nervous system to resist alcohol's actions on cells

C. Learning to perform tasks effectively under alcohol influence

D. Adaptation of neurotransmitter receptors

Answer: B. Adaptation of the nervous system to resist alcohol's actions on cells

Also Read: Nymphomania: Causes, Symptoms, Risk Factors, Diagnosis, Treatment

Hope you found this blog helpful for your Psychiatric Theory and Specialities Preparation. For more informative and interesting posts like these, keep reading PrepLadder’s blogs.