This document provides definitions and information about drugs and their effects on the body. It begins by defining a drug as any substance that can alter homeostasis. It then discusses definitions of drug use, misuse, and abuse. The rest of the document covers topics like the central nervous system, factors that affect drug action, psychological effects of drugs, and terminology related to drug action such as tolerance, withdrawal symptoms, addiction, and habituation.

1. PHARMACOLOGY NOTES
DEFINITION OF A DRUG
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,

2. 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

3. 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-

4. 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:
 Alcohol
 Tobacco
 Sedative-hypnotics
 Cocaine
 Heroin
 Tranquilizers
 Narcotic-analgesics other than heroin
 Amphetamines
 PCP
 Volatile Substances
 Hallucinogens
 Marijuana (Cannabis sativa)
 Antihistamines
 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

5. drugs, you may wish to determine your own rank ordering of the danger of various
drugs to the individual and/or to society.
FACTORS THAT AFFECT DRUG ACTION
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.
Dose
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

6. 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.
Time
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.
PSYCHOLOGICAL EFFECTS OF DRUGS
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

7. 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.
Set
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.
Setting
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.
TERMINOLOGY OF DRUG ACTION
TOLERANCE
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

8. 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
Stimulants are a group of drugs that tend to stimulate the central nervous system.
Habituation to these drugs can occur.
Depressants
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

9. 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
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
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
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.

10. Hypersensitivity
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.
Idiosyncrasy
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.