The document discusses how drugs interact with the human body. It describes how drugs are administered, absorbed, distributed, metabolized and excreted through the process of pharmacology. It then explains how drugs act on various systems in the body like the nervous system, which consists of the central nervous system (CNS), autonomic nervous system (ANS), and peripheral nervous system (PNS). The CNS is made up of the brain and spinal cord. Drugs can affect neurotransmitters like dopamine, serotonin and GABA in the brain. Different parts of the brain are also discussed like the hypothalamus, limbic system, and basal ganglia. The document concludes by explaining how drugs interact with major body systems such

1. Albia Dugger • Miami Dade College
Chapter 5
The Pharmacology
and Physiology
of Drug Use

2. Pharmacology
• Different drugs produce different effects within the psyche
and soma
• The interaction between drugs and living organisms is called
pharmacology
• Drug pharmacology relates to the way it is administered,
absorbed, distributed, metabolized, and excreted
• Drugs that act quickly and produce intense effects are more
likely to be abused than are drugs that act slowly

3. Injected drugs reach the brain quickly

4. Drug Actions
• Drugs affect various organs, including the nervous system.
• The nervous system consists of the central nervous system
(CNS), the autonomic nervous system (ANS), and the
peripheral nervous system (PNS)
• The CNS consists of the brain and spinal cord, and is
composed of nerve cells (neurons)
• Information is transmitted electrically within the neuron, and
chemically between neurons

5. The Neuron
• Dendrites transmit nerve impulses to the nerve’s cell body
(soma)
• Axons send impulses away from the cell body
• Electrical impulses (action potentials) originate in the
dendrite and pass through the cell body via the axon
• Between the axon of one neuron and the dendrite of another
neuron is a space called a synapse

6. Neurons in the Brain

7. The Neuron
• At the ends of axons are saclike vesicles containing
neurotransmitters which cross the synapse to receptor sites
• Chemicals in the receptor sites generate electrical impulses
• Drugs that influencing the release, storage, and synthesis of
neurotransmitters are classified as presynaptic
• Drugs affecting neurotransmitters after they cross the
synapse are classified as postsynaptic

8. Synaptic Transmission

9. Drugs and Synaptic Transmission
• Neurotransmitters linked to addiction include dopamine,
norepinephrine, GABA, and serotonin
• Some drugs increase activity and excitation nerve cells (e.g.
caffeine)
• Sedative-hypnotic drugs make nerve cells less sensitive
• Many nerve cells contain autoreceptors that alter the
synthesis of neurotransmitters (e.g. LSD)

10. Neurotransmitters
• Most drugs affect brain activity by increasing or decreasing
the activity of various neurotransmitters
• Neurotransmitters enable the brain to receive, process, and
respond to information by carrying impulses from one neuron
to the next

11. Acetylcholine
• Acetylcholine (ACH)
• Synthesized from choline and acetyl coenzyme A
• Cholinergic neurons are linked to specific behaviors
• Excitatory neurotransmitter in skeletal muscles
• Inhibitory neurotransmitter in heart muscle
• Reduced ACH receptors associated with Alzheimer’s
• Anticholinergic hallucinogens interfere with ACH
• Cholinesterase inhibitors such as nerve gas

12. Serotonin
• Serotonin
• Inhibitory neurotransmitter in the upper brain stem
(tryptaminergic neurons)
• Helps regulate pain, sensory perception, eating, sleep,
and body temperature
• Excessive reabsorption results in depression
(antidepressant drugs SSRIs)
• Related to hallucinations, psychosis, obsessive-
compulsive disorder, aggression or violence
• Amino acid tryptophan is needed to synthesize serotonin
in tryptaminergic neurons

13. How Drugs Work

14. Gamma-aminobutyric Acid (GABA)
• Gamma-aminobutyric acid (GABA)
• Inhibits nerve impulses from being sent from one neuron
to another
• Alcohol stimulates GABA, producing relaxation and
feelings of decreased inhibition
• Barbiturates and minor tranquilizers also increase the
action of GABA

15. Catecholamines
• Catecholamines
• Epinephrine, dopamine, and norepinephrine
• Reabsorbed by the neuron that makes them (reuptake)
• Increase causes stimulation; decrease causes depression
• Amphetamines and cocaine initially increase
catecholamines, followed by depletion
• Dopamine levels are influenced by marijuana, nicotine,
heroin, and amphetamines
• Epinephrine released in fight-flight-fright syndrome
• Mescaline and MDMA (Ecstasy) reduce norepinephrine

16. Fight-Flight-Fright Mechanism

17. Peptides
• Peptides
• Substances in which amino acid sequences are linked
• Modulate the activity of transmitters
• Natural endorphins have opiate-like properties
• High levels of endorphins in the brain (enkaphalins) could
be a factor in morphine dependency
• Chronic alcohol use impairs endorphin production

18. Effects of Selected Neurotransmitters

19. Central Nervous System (CNS)
• The CNS consists of the brain and spinal cord
• Messages are transmitted from the brain to the muscles and
organs and back to the brain through the spinal cord
• The type of message depends on which part of the brain is
sending it

20. Cross Section of the Human Brain

21. Reticular Activating System (RAS)
• Reticular Activating System (RAS)
• Part of the central nervous system
• Affects sleep, attention, and arousal
• Shuts down during sleep
• Many drugs, including barbiturates, LSD, alcohol, and
amphetamines, affect the RAS extensively
• Stimulants activate the RAS

22. Hypothalamus
• Hypothalamus
• Gland situated near the base of the brain
• Maintains homeostasis
• Controls the pituitary gland, which regulates hormones
that affect stress, aggressiveness, heart rate, hunger,
thirst, consciousness, body temperature, blood pressure,
and sexual behavior
• Linked to behavioral and chemical dependencies from
alcohol to gambling to obesity

23. Cerebral Cortex
• Cerebral cortex
• Part of the cerebrum involved in intellectual functioning
• Affects speech, motor movement, sensory perception,
hearing, vision, sensory discrimination, memory,
language, reasoning, abstract reasoning, and personality
• Affected by almost all psychoactive drugs

24. Limbic System
• Limbic system
• Part of the central nervous system that plays a key role in
memory and emotion
• Consists of many diverse structures in the cerebral
hemispheres
• Cocaine affects neurotransmitters in the limbic system,
creating intense feelings of excitement and joy
• Depressants reduce electrical activity in the limbic system,
producing feelings of tranquility and relaxation

25. Limbic system Regulates Anger
and Hostile Behaviors

26. Medial Forebrain Bundle
• Medial forebrain bundle (MFB)
• Serves as a communication route between the limbic
system and the brain stem
• Affects pleasure and reward
• Sensation of orgasm originates here
• Amphetamines and cocaine produce intense euphoria

27. Basal Ganglia
• Basal ganglia
• Part of the central nervous system which maintains
involuntary motor control
• Regulates abilities to stand, walk, run, carry, throw, and lift
• Parkinson’s disease destroys the basal ganglia
• Drugs prescribed for schizophrenia can precipitate
Parkinson’s-like behavior
• China white (fentanyl) has been linked to brain damage
similar to Parkinson’s disease

28. Periventricular System
• Periventricular System
• Composed of nerve cells above and to either side of the
hypothalamus
• Implicated in punishment or avoidance behavior
• Coupled with the MBF in that stimulation of one inhibits the
other

29. Brain Stem
• The brain stem is located at the point where the brain and
spinal cord join
• It consists of the medulla oblongata, pons, and midbrain
• Regulates functions such as breathing, heartbeat, dilation of
the pupil of the eye, blood pressure, and the vomiting reflex
• Drugs affecting the brain stem include alcohol and opiates

30. Actions of Various Parts of the Brain

31. Peripheral Nervous System
• Peripheral nervous system (PNS)
• Consists of the somatic and autonomic nervous systems
• Somatic nervous system
• Part of the nervous system that controls movement of the
skeletal muscles
• Autonomic nervous system (ANS)
• Part of the peripheral nervous system that is automatic
and involuntary

32. Autonomic Nervous System
• The autonomic nervous system (ANS) regulates blood
pressure, gastrointestinal and urinary functioning, body
temperature, sweating, and other involuntary bodily functions
• Divided into two branches which work in opposition:
• Sympathetic nervous system reacts to situations that
require fighting or fleeing (fight-flight-fright syndrome)
• Parasympathetic nervous system allows the body to
achieve a resting state

33. Comparison of Sympathetic and
Parasympathetic Systems

34. Autonomic Nervous System
• Drugs that mimic actions of the sympathetic system are called
sympathomimetics
• Examples: Amphetamines, cocaine, and caffeine
• Drugs that mimic actions of the parasympathetic system are
called parasympathomimetics
• Examples: Nicotine and the hallucinogen Amanita muscaria

35. Drugs and Major Body Systems
• Endocrine System
• Hormones stimulate growth of new tissues, store nutrients,
maintain homeostasis, and affect metabolism and sexual
behavior
• The hypothalamus controls the endocrine system and the
pituitary gland
• The adrenal glands, secrete adrenaline and cortisol
• Many synthetic hormones are used as drugs

36. Drugs and Major Body Systems
• Cardiovascular System
• Drugs that interfere with the heart’s ability to contract
present a danger
• Alcohol can cause the heart muscle to degenerate, induce
cardiac arrhythmia, and increase blood pressure
• Cocaine increases heart rate and blood pressure, and is a
vasoconstrictor
• Cigarettes raise blood pressure and reduce oxygen
• Marijuana causes tachycardia

37. Drugs and Major Body Systems
• Respiratory System
• Depressant drugs such as barbiturates, minor
tranquilizers, alcohol, and narcotics slow respiration
• Combining depressants with other drugs can have a
synergistic effect
• Stimulants such as amphetamines and cocaine increase
respiratory rate
• Cigarette smoke impedes cilia from removing mucus and
other foreign matter from the lungs

38. Drugs and Major Body Systems
• Gastrointestinal System
• Antacids containing sodium bicarbonate, calcium
carbonate, aluminum hydroxide, or magnesium salts are
used to neutralize stomach acid
• Laxatives are used to relieve constipation
• Alcohol causes diarrhea and irritates the stomach, small
intestine, esophagus, and pancreas

39. Factors Influencing the Effects of Drugs
• Age
• Infants and the elderly are more sensitive to the effects of
drugs than people between these two life stages
• Drug actions are prolonged because they are less able to
metabolize and excrete drugs
• Tolerance for alcohol lessens as people age
• Some drugs accumulate in adipose tissue, increasing
sensitivity and the possibility of a toxic reaction
• Elementary-age children respond differently to drugs

40. Elderly use the most prescription drugs

41. Factors Influencing the Effects of Drugs
• Gender:
• Women are more sensitive to drugs because fat stores
drugs and water dilutes drugs in the bloodstream
• Females are especially affected by drugs during the
premenstrual phase of the menstrual cycle and pregnancy
• Teratogenic drugs damage the developing fetus
• Use of tobacco, coffee, and alcohol during pregnancy
increases the risk of miscarriages

42. Emergency Department Visits by Gender
Males Females
All illicit drugs 640,704 352,136
Cocaine 306,651 175,465
Heroin 138,607 62,018
Marijuana 245,553 128,435
Stimulants 52,189 39,744
MDMA 9,439 8,425

43. Factors Influencing the Effects of Drugs
• Dosage
• The smallest amount of a drug required to produce an
effect is the threshold dose
• The amount necessary to achieve a specific response is
the effective dose (ED)
• The quantity required to cause death is the lethal dose
(LD)
• A dose-response curve represents the effects of drugs at
various levels

44. Dose-Response Curve

45. Purity and Potency
• Many problems arise from impurities rather than from the
drugs themselves
• The purity of drugs varies greatly among illegal drugs –
heroin has varied from 4% to 69%
• Potency refers to a drug’s ability to produce an effect relative
to other drugs – some drugs vary naturally in potency

46. Drug Interactions
• An estimated 25% of admissions to emergency rooms result
from interactions between alcohol and medications
• The effects of combining drugs and food can be additive,
antagonistic, or synergistic
• Taking certain antidepressants with certain foods can result in
hemorrhaging and stroke
• More than 150 prescription and over-the counter medications
interact negatively with alcohol

47. Drug Interactions with Alcohol

48. Drug Interactions with Alcohol

49. Tolerance
• Tolerance
• Progressively decreasing responsiveness to a drug
• Pharmacological tolerance
• Adjustment or compensation of the body to the presence
of a given drug
• Behavioral tolerance
• Adjustment or behaviors learned by an individual to
compensate for the presence of drugs

50. Tolerance
• Cross-tolerance
• Transference of tolerance to a drug to chemically similar
drugs
• Reverse tolerance
• A drug user’s experiencing of the desired effects from
lesser amounts of the same drug

51. Set and Setting
• The effects of drugs on behavior depend on one’s attitudes
toward drugs, emotional state, and previous experiences
• Set
• The psychological state, personality, and expectations of
an individual while using drugs (internal environment)
• Setting
• The physical and social environment in which drugs are
used (external environment)

52. Set and Setting
• Placebos are inert substances capable of producing
psychological and physiological reactions
• Placebo prescriptions are effective because of expectations
for the drug
• The notion of a drug being euphoric or dysphoric depends a
great deal on set
• To a large extent, setting determines set

53. Methods of Administration
• Oral Ingestion
• Drugs can be consumed in the form of pills, liquids,
tablets, or capsules
• Convenient and safe
• Not appropriate in emergencies
• Slow absorption rate may reduce the amount of the drug
to an insufficient level
• Can choke on a drug if not conscious
• Some ingested drugs cause nausea and vomiting
• Because conditions in the gastrointestinal tract change
constantly, drug absorption is variable

54. Methods of Administration
• Injection (parenteral drug use)
• Reach the brain quickly but carry many risks
• In intravenous injection, or mainlining, drugs are
administered directly into the bloodstream
• In intramuscular injection, drugs are injected into muscle
tissue
• Injecting drugs just below the layers of the skin is called
subcutaneous injection
• Unsterile needles pose risk for infectious diseases such as
AIDS

55. AIDS Cases by Transmission Category

56. Risks associated with injected drug use

57. Methods of Administration
• Topical application (transdermal method)
• Drugs applied to the skin and absorbed into the
bloodstream by placing small disks or patches behind the
ear or on the arm or chest
• Introduces drugs into the body slowly
• Drugs are absorbed directly into the bloodstream at
programmed rates
• Used to relieve motion sickness, angina pectoris, and
nicotine dependency

58. Methods of Administration
• Inhalation
• Drugs absorbed into the bloodstream via the lungs
• Fast and efficient
• Irritates the lungs
• Inhaled drugs include volatile anesthetics such as glue,
paint thinner, and gasoline, in addition to cigarettes,
marijuana, and crack cocaine