Adapted from Engs, R.C. Alcohol and Other Drugs: Self Responsibility, Tichenor Publishing Company, Bloomington, IN, 1987. (c) Copyright Ruth C. Engs, Bloomington, IN, 1996

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A drug is defined as any substance that can alter the homeostasis of the body. Individuals consuming these substances can be described as using, misusing, or abusing drugs or any other substances. Definitions of Drug Use, Misuse, and Abuse

Drug Use-Drug use is using any substance for its intended purpose. Drug use would include taking an antibiotic or sleeping pill as prescribed, using an occasional antacid, drinking wine with dinner, or a cup of coffee at breakfast.

Drug Misuse-Drug misuse is use of a drug that may result in transient physical, mental, or social problems. Drinking alcoholic beverages or smoking marijuana for improved social skills would be drug misuse. Giving a prescription to a friend or family member because he or she has the same symptoms as you do, or taking more of a medication and at more frequent intervals than prescribed, would also be considered drug misuse.

Drug Abuse-Drug abuse is use of a substance that results in long-term physical, mental, or social problems. Using heroin or barbiturates to get high repeatedly, becoming dependent upon alcohol, or smoking marijuana continuously to escape the realities and responsibilities of life would be examples of drug abuse. Using a laxative every day would also be considered to be drug abuse.

Central Nervous System

Cerebral Cortex. The cerebral cortex is the outer gray matter covering each hemisphere of the brain. The cerebral cortex contains a motor and speech center, visual, olfactory, and auditory parts-along with areas concerned with higher mental activity such as judgement, memory, reasoning, and thought. Drugs that depress the cellular activity in the cerebrum, such as the opiates, barbiturates, and alcohol, may decrease the acuity of perception and sensations, and decrease alertness and concentration. Drugs that increase the cellular activity in the cortex may cause more vivid impulses to be received with greater awareness of surroundings and even hallucinations. Information on the awareness of pleasure or pain and other sensory impulses is received in this area of the brain from the body via the thalamus. Thalamus. The thalamus is the relay center of the brain. All incoming and outgoing signals pass through this area. It can relay signals from the brain stem to all parts of the cerebral cortex and cause a generalized activation of the cerebrum. The thalamus is the center for sensations such as the agreeableness or disagreeableness of a situation. Depression of this part of the brain from depressants such as tranquilizers and opiates may block off unpleasant sensations to the cortex and cause the person to feel good.

Hypothalamus. The hypothalamus lies below the thalamus and is directly connected to it. It contains centers that regulate body temperature, fat and carbohydrate metabolism, water balance, hunger and satiety, and pleasure and pain. There are also pain centers in the limbic system. Depressants acting in this area can cause the person to be sleepy, and substances such as aspirin can affect the heat-regulating center. Natural sleep chemicals produced by the brain, such as delta-sleep-inducing peptides, react in this part of the brain. Amphetamines and other stimulants appear to act on this area to stimulate the satiety and the pleasure centers, causing the person to feel good, alert, and not hungry. The major pleasure center of the brain is thought is to be located in the hypothalamus. Stimulation of this area results in such feelings as orgasm, joy, and extreme pleasure. The positive high and good feeling produced by drugs are also thought to originate here. The hypothalamus is directly linked to the autonomic nervous system. Many psychosomatic illnesses including ulcers and hypertension are thought to result from overstimulation of this center, which in turn activates the autonomic nervous system. It is thought that most drugs used for recreational purposes exert their major effect in this area of the brain.

Limbic System. The limbic system includes the thalamus, hypothalamus and other structures. The limbic system appears to be the memory site of emotions. If a certain drug is associated with pleasure, the emotional content of the experience is stored in this system and may become a stimulus for repeating this experience. The feelings of anger, joy, and remorse are also thought to occur here.

Reticular Activating System. The reticular activating system receives input from all parts of the sensory system as well as the cerebrum. The major function of this system is to control the arousal level of the brain. This system secretes norepinephrine and dampens the many stimuli coming through it, so new and different stimuli can be recognized by the rest of the brain. If the stimulus is new it will be selected out; if it is not new or is routine it is usually ignored. As an example, if while you are sleeping you are getting cold because you do not have enough covers over you, this system will stimulate the cortex and wake you up. It is thought that in hyperactive children all incoming signals are sent into the rest of the brain for attention and that stimulants, such as Ritalin(R), given to these children stimulate underworking cells to produce this selectivity effect. Depressants such as barbiturates depress this system and produce sedation and loss of consciousness. Stimulation of this part of the brain with amphetamines, caffeine and other stimulants can cause a person to feel alert, awake, and very good. Such stimulation can also cause the distortion of sensations. LSD and Cannabis sativa are thought to affect this part of the brain by creating changes in sensory feelings.

Cerebellum. The cerebellum controls balance and coordination of various body movements. It is also the center for muscle coordination and tone and equilibrium. The cerebellum receives incoming messages from the cortex, spinal sensory nerves, and balance system in the ear, and from the auditory and visual system. Depressant drugs such as barbiturates and alcohol can depress the cells in this center and cause incoordination in body movement and balance. Stimulants can cause tremors.

Medulla Oblongata. The medulla oblongata in the brain stem is the center for such vital functions as respiration, coughing, vomiting, and cardiac and vasomotor control. If overdoses of depressants, such as alcohol and barbiturates, are taken together, this center may cease to function, and the individual could die of suffocation and heart stoppage. Stimulation of this area can cause vomiting.

Harm to the individual and Society

Drugs can be classified or rank ordered according to their hazard potential to the individual and/or society. Harm to the individual would include-

significant organ or tissue damage potential for tolerance physiological or psychological addiction harm to an unborn child increased death rate from use or abuse of the substance Harm to the society would include-

increased rates of death of others (i.e. drunk driving) increased insurance rates loss of working days crimes of violence disability payments family breakdown and mental, physical, or sexual abuse from the use or abuse of the substance

Current research has led to the formulation of the following rank ordering of drugs, in terms of degree of harm to the individual and to society:

1. Alcohol

2. Tobacco 3. Sedative-hypnotics 4. Cocaine 5. Heroin 6. Tranquilizers 7. Narcotic-analgesics other than heroin 8. Amphetamines 9. PCP 10. Volatile Substances 11. Hallucinogens 12. Marijuana (Cannabis sativa) 13. Antihistamines 14. Xanthines

It should be noted that this rank ordering of drugs, is, of course, open to debate, as there are many opinions as to what might or might not be harmful to the individual and to the society. As an example, is it worse for a pregnant woman to drink heavily during pregnancy, producing a mentally and physically handicapped baby, or for someone to rob and maim a person to obtain money for heroin, or for a bright student to neglect family, friends, studies, and possible future by heavily using and selling marijuana and hallucinogens? The potential debate in the rank ordering and classification of drugs by their harmful effect or legality suggests that all classifications and rank ordering are open to criticism and are dependent upon varied opinions, values, and ways of looking at drugs and their use in a society. It also suggests that even though some substances may be legal for consumption in our culture, they may cause serious harm to the individual and to society. Therefore, after studying information in this text and other references concerning drugs, you may wish to determine your own rank ordering of the danger of various drugs to the individual and/or to society.


Many factors must be considered relative to the effect of drug action on the body. First, different drugs exert different effects on various body cells, and unless a substance is able to exert an influence on some body cell or process, no reaction to the substance will take place. Second, before a drug enters the body, three important factors will affect the response of the person to the drug, namely its dose the time it takes it to be effective, and the route of administration. Other factors, such as the individual's psychological environment, metabolism rate, excretion route, age, weight, sex, and hereditary influences, can also affect the action of any drug on the individual. The effect of a drug on the body depends upon (1) its interaction with a body cell and (2) the function of that cell in the body. In most cases, the drug must bond with the cell membrane in order for any action to take place. The point on the cell where the interaction takes place is called the receptor site. The drug-receptor site interaction has often been described as a "lock and key" relationship. The specificity of the drug action among chemically related drugs usually depends upon the degree of fit between the drug and its receptor molecule. The exact mechanism of how this works in the case of many drugs still is not known. Some drugs, however, act on the cell from the point of the receptor site in the following ways:

1. Increase activity of cell. 2. Decrease activity of cell. 3. Block activity of cell. 4. Replace missing component needed by cell. 5. Aid in transferring substance through cell membrane.

In some cases, after a drug enters the body, it must be chemically altered before it is able to exert any effect on the body cells. This can occur at the cellular receptor site or in the stomach or intestines.


The response differs for all drugs in the intensity and types of effects according to the dose (amount) of the drug given. Most drugs do not show an effect until a certain minimal level of dosage is reached. The smallest dosage of the drug to show an effect is the threshold of the drug. As the result of heredity, different people respond in a different manner to the same dosage of a drug. The dose of a drug required to produce an effective response in 50 percent of the people tested is called the median lethal dose. Obviously, this latter dosage is only given to experimental animals when testing drug safety. In most cases, the more of a drug one takes, the stronger effect of the drug. However, the increased dosage is often detrimental to the individual, as a lethal dosage may be reached. For example, if one wishes to get slightly high, to feel relaxed, and still remain in control, one might drink a glass of wine during one hour before dinner with a friend. This could be called the effective dose of the alcohol if this were the purpose of using this drug. To increase the dosage to three or six glasses of wine in an hour would probably result in such effects as decreased reaction time, slurring of speech, sleepiness, uncoordinated movements, difficulty in speaking, and a bad hangover the next day. A still greater number of glasses of wine in an hour could result in a coma or even in death. In the case of alcohol, an increase in the dose intensifies the reaction of the drug but does not increase the desired effect sought by the drug user. This would also be true of other drugs. For example, an increase in the dosage of penicillin for a "strep" sore throat will not cure the problem any faster.


The time that it takes for a drug to exert its desired effect once it has entered the body is also important. Some drugs act immediately upon entering the circulatory system, and other drugs take hours and sometimes even days to exert their desired effects. Drugs that act immediately are termed short-term and often require only single doses, whereas other drugs must be given in repeated dosages to be effective and are often called long-term effect drugs. As an example, adrenalin (epinephrine) will act immediately upon inhalation or injection, whereas an antibiotic such as penicillin may take hours or even a day or so for it to be effective, no matter if it is given by injection or by mouth.

Route of Administration

A very important factor influencing the reaction of drugs in the body is the method by which it is administered.

Oral. Perhaps the most common way of taking drugs is orally (by mouth). This is the most convenient method for most people to take drugs and permits digestion to modify drugs that might be too powerful or too fast acting if administered directly into the bloodstream. Once in the stomach, some drugs, such as alcohol, can go directly into the bloodstream without further digestion. However, most drugs are absorbed into the circulatory system along with glucose, amino acids, minerals, and vitamins, after being passed into the large or small intestine. Drugs that are soluble in lipids (fats), such as barbiturates, vitamins D and E, and THC, the active principle in marijuana, tend to remain longer in the body. Water-soluble drugs , such as vitamin C, alcohol, and antibiotics used for urinary tract infections, tends to be excreted rapidly by the kidneys. The major detoxification organ of the body is the liver, which removes chemicals and toxins from the blood and renders them harmless and easier to excrete. The elimination of most substances takes place in the urinary tract and the anal canal. However, excretion of some drugs can also take place through the respiratory system and skin.

Inhalation. Some drugs, such as anesthetics, nicotine in cigarettes, solvents, marijuana, and drugs for treating lung disorders, are inhaled through the mouth. Cocaine and some forms of amphetamine are usually inhaled through the nose, where it is absorbed through the mucous membrane in the nostrils. Because the lungs have large beds of capillaries, inhaled chemicals are capable of crossing the membranes to enter the blood fairly rapidly. A problem with inhaling drugs such as tobacco, marijuana, and cocaine, is that they irritate the mucous membrane lining found in the respiratory tract.

Injection. Injection is a common way of administering drugs, particularly in a hospital or medical setting. Injection is also used on the street with opiates and sometimes with cocaine and heroin. Drugs taken by injection can be intravenously, intramuscularly, or subcutaneously administered. In intravenous injections, the drug can go directly into the circulatory system and act immediately. Drugs such as heparin (reduces clotting of blood), some antibiotics, glucose and salt solutions, and drugs given to cancer and heart attack patients and in emergency situations are often given intravenously. Intravenous injections can be dangerous because of impurities found in many street drugs, errors in dosage, bubbles in the syringe, and infection from puncturing the skin and vein. Intramuscular injections are given in the large muscles of the buttocks, upper leg, or arm and are used for drugs that need to be fairly rapidly absorbed into the circulatory system, such as antibiotics and narcotic-analgesics. Subcutaneous injections are given right beneath the skin and are used for drugs that are rendered inactive by the digestive system, such as heparin, and insulin and for drugs that need to be absorbed more slowly into the circulatory system.

Rectally or Vaginally. The rectum will absorb many drugs. Suppositories containing sleeping aids, such as chloral hydrate, tranquilizers, such as Thyroxin(R), and antinausea medication, such as Compazine(R), are commonly given to elderly or extremely sick people who are unable to swallow medications. Vaginal medication is usually used to cure local infections caused by various organisms. Cutaneously. Some drugs and substances can be absorbed directly through the skin. Various "sore ligament" preparations would be an example of these, along with cortisone in the treatment of poison ivy. The absorption, of course, is usually very slow.


The psychological setting or frame of mind is important in the effect of many drugs, particularly with psychotropics. Psychological effects are also important for other medications and treatments and often result in cures or symptomatic relief when no drugs has actually been given. There are several psychological aspects of drug use, including the placebo effect, set and setting, which are discussed below.

Placebo Effect

If a person thinks that he or she is taking a certain drug that is supposed to have a certain effect, and it does (whether or not it contains any active ingredients designed to produce the desired results), this is the placebo effect. This effect can happen with any substance; it is important in medicine and probably has resulted in many "cures" of a variety of ailments. An example of the placebo effect is chicken soup taking away the symptoms of a cold, or hot lemon tea eliminating a headache.


Psychological or mental set is the frame of mind a person is in when he or she takes a drug. It is also considered to be an unconscious expectation and is a factor in the placebo effect. If a person does not think that a certain medication will work, it often does not.


The actual physical, social and cultural environment in which a person finds him/herself when a substance is consumed can determine how that person reacts to a drug. As an example, a glass of wine in a fine crystal wine glass, sipped in a candlelit restaurant with music playing in the background will have a different effect than the same wine drank from a paper cup in a classroom.



Tolerance to a drug develops when the response to the same dose of the drug decreases with repeated use. As an example, if you are an occasional drinker, you may become intoxicated after drinking three beers. However, after drinking every night for a week, you may find that it takes five beers to get that same feeling. This would indicate a developing tolerance to alcohol. The rate at which an individual develops tolerance to a drug depends upon that individual's heredity, the dose of the drug, the size of the person, and the frequency of drug administration. Tolerance usually occurs with depressants, which include alcohol, opiates, synthetic narcotics, barbiturates, some minor tranquilizers, and volatile substances such as ether and glue. Tolerance to amphetamines when used in large doses has also been found.

Withdrawal Symptoms

When one has become physically dependent upon a drug and abruptly abstains from the substance, a psychological and/or physiological reaction occurs. The reaction is the opposite of the effect of the drug. In withdrawal from a depressant drug, restlessness, irritability, nausea, tremors, inability to sleep, and sometimes, in the case of alcohol and barbiturates, convulsions that may lead to death may occur.

Addiction (Physical Dependence)

Addiction has often been considered to be physical dependence upon a drug. This generally occurs with depressant drugs, which include alcohol, barbiturates, tranquilizers, and opiates. Increased tolerance to the substance and withdrawal symptoms upon cessation of use are usually present. However, according to L.J. Hatterer, "we now extend addiction to relate to almost any substance, activity or interaction, as well as to drugs". The individual has an overpowering need for the substance, object, or activity that produces a psychological and/or physiological high. The desire or need is repetitive, impulsive, and compulsive in nature. If the person ceases the activity or abstains from the substance, withdrawal symptoms usually occur.

Habituation (Psychological Dependence)

Habituation was at one point considered to be psychological dependency upon a substance or activity. However, with the expanded definition of addiction to include the addictive behaviors or the addictive process, which can apply to any activity, interaction or object, this term is not used as frequently as it was in the past. Psychological withdrawal symptoms, including irritability, depression, and sleep disturbances often accompany habituation.


Stimulants are a group of drugs that tend to stimulate the central nervous system. Habituation to these drugs can occur.


Depressants are a group of drugs that depress the central nervous system. Tolerance and physical dependency are common with them. More information about depressants is given in later chapters.

Cross Tolerance and Cross Dependence

Cross tolerance refers to the fact that if a person has developed a tolerance to a drug in a certain classification, such as the depressants, that person is more likely to develop tolerance with another drug in that classification. As an example, people who are dependent upon alcohol show an increased tolerance to barbiturates, synthetic and natural opiate narcotics, and anesthetics. This, of course, means that the person must have a higher dose of the new drug for it to be effective. In cross dependence, the withdrawal symptoms from one drug in a classification can be relieved by another. As an example, many alcoholics are given barbiturates and tranquilizers to prevent withdrawal symptoms. However, the person may soon develop a dependency on the other drug as well.


Potentiation occurs when two drugs are taken together and one of them intensifies the action of the other. This could be expressed by a +b= B. As an example, Phenergan(R), an antihistamine, when given with a painkilling narcotic such as Demerol(R) intensifies its effect, there by cutting down on the amount of the narcotic needed.


Synergism is similar to potentiation. If two drugs are taken together that are similar in action, such as barbiturates and alcohol, which are both depressants, an effect exaggerated out of proportion to that of each drug taken separately at the given dose may occur. This could be expressed by 1+1= 5. An example might be a person taking a dose of alcohol and a dose of a barbiturate. Normally, taken alone, neither substance would cause serious harm, but if taken together, the combination could cause coma or death.

Additive Effect

Additive effect is the term used when two or more drugs are taken at the same time and the action of one plus the action of the other results in an action as if just one drug had been given. This could be represented by 1+1= 2. An example would be a barbiturate and a tranquilizer given together before surgery to relax the patient.


Antagonism is action in which two drugs given together will have an opposite effect on the body. This could be expressed by 1+1=0. An example might be the use of a tranquilizer to stop the action of LSD. Some stimulants will counteract the effects of depressants and thus are used to treat overdoses of barbiturates and narcotics.


One of the biggest problems with many drugs, especially antibiotics, is an allergic or hypersensitive reaction. An allergic reaction can range from hives, itching, and nausea to a shock in which the person can die. The allergic reaction occurs after the first time the person has been exposed to the drug, not the first time the drug is taken. It should be noted that a person can use a drug for years without any adverse reaction and then become hypersensitive to it. This sometimes occurs to individuals handling drugs, such as nurses, pharmacists, and veterinarians.


When a person exhibits an abnormal or peculiar response to a drug, it is called an idiosyncratic response to that drug. An example would be a person who becomes nervous or excited after being administered a sleeping medication such as a barbiturate.

Side Effects

Most substances have side effects that may or may not be harmful to the individual. A side effect is an effect of the drug other than the one for which it was administered. The main effect and side effects of a drug sometimes depend upon the purpose of its administration. As an example, antihistamines are often given to dry and reduce swollen nasal passages caused by allergies. However, antihistamines can also cause sleepiness, which would be the side effect. The main effect of sleepiness is used by manufacturers of over-the-counter sleep aids to produce drowsiness and promote sleep. In this case, a side effect of the medication would be the drying of the nasal passages. Some side effects can cause serious problems, such as abnormal production of red blood cells called aplastic anemia, or stomach bleeding from the consumption of too much aspirin. These more serious side effects are called untoward actions.