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1. CNS Pharmacology-
Introduction to Drugs of Abuse I
Clinical:
E-Medicine Article
Injecting Drug Use
Prepared and Presented by:
Marc Imhotep Cray, M.D.
Professor Pharmacology

2. Definitions
I. Drug abuse
II. Drug dependence
A) Psychological dependence
B) Physiological dependence
III. Drug addiction
IV. Drug tolerance
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3. I. Drug abuse
Inappropriate and usually excessive, self-
administration of a drug for non-medical purposes
 Almost all abused drugs exert their effects in the CNS
 Drugs with high abuse potential have a tendency to
induce compulsive drug-seeking behavior
 Preoccupation with the procurement and use of the drug
may be so demanding as to decrease the users
productivity.
 In addition, prolonged abuse may cause chronic toxicity
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4. II. Drug dependence
Repetitive use of substances that produce
an optimal state of well being because of
their positive reinforcing effects in the
CNS
A) Psychological dependence.
B) Physical dependence.
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5. II. Drug dependence
A) Psychological Dependence
 Motivational component: great subjective need,
compulsion, drive to get the drug
 Will take drug periodically
 Although physical dependence for a drug may
not occur, “drug-seeking behavior” is present
 Habituation; Just "like" the drug; Drug effects
serve as “positive reinforcers”
No tolerance increase
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6. II. Drug dependence
B) Physiological Dependence
 The body needs the drug for normal
physiological function
 Tend to increase dose because of tolerance.
 Physical withdrawal symptoms (negative
reinforcement)
 Predictable group of signs and symptoms
resulting from abrupt removal of a drug
 Psychological dependence is also present
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7. III. Drug addiction
 The drug-use and drug-seeking behavior of
dependent individuals is maintained by the
reinforcing central activity of the drug despite
its negative social, psychological and physical
consequences
 Physiological effects, including negative
reinforcers such as symptoms of withdrawal may
also be involve.
 High tendency to relapse
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8. IV. Drug tolerance
 After chronic use, the
same amount of drug
is insufficient to cause
the desired effect and
thus, more drug is
used
 A compensatory
responseDrug Dose
Normal
Tolerance
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9. IV. Drug tolerance cont.
A) Innate Tolerance
1. Sensitivity
2. Insensitivity
B) Acquired Tolerance
1. Pharmacokinetic or metabolic
2. Pharmacodynamic or functional
3. Learned or behavioral
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10. V. Cross-dependence
 When a drug is administered to achieve
the same outcome as that of another
drug
 i.e. heroin  methadone
In a heroin user, methadone can be
substituted for heroin in preventing
the withdrawal syndrome
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11. VI. Cross-tolerance
 When an individual has become tolerant to
a drug and requires higher than normal
doses of a second drug to have its effects
i.e. Barbiturates  BDZ
Amphetamine  Cocaine
BARBs  Anesthetics
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12. VI. Cross-tolerance
 In general there is cross-dependence and cross-tolerance
between drugs of the same class, but not between drugs in
different classes
There is some cross-tolerance btw sedative-hypnotics and
volatile intoxicants; thus a person tolerant to barbiturates will
require more anesthesia than a non-tolerant person
 LSD type drugs (tryptamine group) and phenylethylamines
have cross-tolerance for each other but not with other
hallucinogens
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13. VII. Co-administration/Co-abuse
 Drugs of abuse are used in combination with
other drugs from one or more categories
 Alcohol is used, for example, with almost
everything else
 Smoking (nicotine intake) is prevalent in
patients using other drugs
 Be aware of the possibility of combination
of drugs when treating intoxication,
withdrawal or overdose, each drug will
require a specific treatment
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14. Take home Point
Because of the diverse character of these drugs,
there is no “single reason” for their use, nor is
there an “addictive personality".
IT IS NOT NECESSARY TO HAVE A PREEXISTING
EMOTIONAL OR PSYCHIATRIC PROBLEM TO
BECOME DRUG DEPENDENT!!!
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15. VIII. Toxicology
A) Tissue and organ toxicity
- Usual dose vs overdose
- Acute use (respiratory depression -
narcotics, coma-barbiturates;
cardiovascular effects and seizures-
cocaine;arrhythmias-volatile intoxicants)
- Chronic use (alcohol, tobacco)
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16. VIII. Toxicology
B) Psychic toxicity
- Acute use (bad trips, flashbacks -
hallucinogens; CNS stimulants).
- Chronic use (alcohol,
hallucinogens, stimulants =>
reality distortion).
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17. VIII. Toxicology
C) Behavioral toxicity
- Amotivational syndrome, loss of
productivity loss of psychomotor control,
accidents, violence
- Acute use (alcohol, stimulants, PCP)
- Chronic use (alcohol, CNS depressants,
stimulants, hallucinogens, PCP)
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18. VIII. Toxicology
D) Associated Diseases
- Infections, AIDS, venereal diseases,
tobacco-related fires, toxicity due to bad
batches of drug (MPTP, PCP congeners),
car accidents, big machinery accidents,
other accidents, violent death
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19. Also see:
Mouse Party University of
Utah, Genetic Science
Learning Center
The Science of Addiction
University of Utah, Genetic
Science Learning
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47. Drugs and Neurotransmitters & Mental
Disorders Interactive Tutorials and
Animation Learning Tools
 Psychotropic Medications and Neurotransmitters
Wisconsin Online
 Alcohol and the brain from PBS
 The Effect of Drugs and Disease on Snaptic
Transmission Harvard Education
 Nicotine Patch by Nucleus Communications
 GABA Inhibition of Glutamate Bay Area Pain Medical
Associates
 Acute Pain Bay Area Pain Medical Associates
 How Drugs Affect Neurotransmitters INMHA
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48. Drugs and Neurotransmitters & Mental
Disorders Interactive Tutorials and
Animation Learning Tools
 Schizophrehia UNIVERSITY OF CENTRAL LANCASHIRE
 Epilepsy UNIVERSITY OF CENTRAL LANCASHIRE
 Pharmacologic Action of Meth RnCeus.com
 How is Pain Produced University of Edinburgh
 How Much Alcohol can YOU TAke BBC
 The Brain: Understanding Neurobiology Through the Study of Addiction
National Institutes of Health
 The Science of Addiction University of Utah, Genetic Science Learning
Center
 Stimulants and Antidepressants Dr. Ian Winship of the University of
Alberta
 Tranquilizers and CNS Depressants Dr.Ian Winship of the University of
Alberta
 Genetics of Addiction Genetics Science Learning Center
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49. eMedicine Articles on Addiction
 Alcohol-Related Psychosis
 Alcoholism
 Amphetamine-Related
Psychiatric Disorders
 Caffeine-Related Psychiatric
Disorders
 Cannabis Compound Abuse
 Cocaine-Related Psychiatric
Disorders
 Hallucinogens
 Inhalant-Related Psychiatric
Disorders
 Injecting Drug Use
 Nicotine Addiction
 Opioid Abuse
 Phencyclidine (PCP)-Related
Psychiatric Disorders
 Sedative, Hypnotic,
Anxiolytic Use Disorders
 Stimulants
 Substance-Induced Mood
Disorders: Depression and
Mania
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