and Drugs Behavior
Drugs
How and Why
Drugs Work
PSY 291
PSY
Intended and Unintended Effects of Drugs
Intended
Intended vs. Unintended
Drug Effects
Intended responses:
reason for using the drug
Unintended responses:
side effects
The main distinction
between intended
responses and side
effects depends on the
therapeutic objective.
5 Common side effects
Common
Nausea or vomiting
Nausea
Changes in mental alertness
Changes
Dependence
Dependence
Allergic reactions
Allergic
Changes in cardiovascular activity
Common side effects of drugs
Common
Factors Affecting
Individuals Response
Individuals
Drug concentration
Dose-response
Threshold / Plateau
Potency
Potency
Toxicity
Toxicity
Dose-Response Curve
Dose-Response
Relationship between
amount of drug and
response.
High individual
variability makes it
difficult to predict
precise response to
drug.
Drug Concentration
Drug
Threshold dose
Threshold
minimum amount of a drug necessary to have an
minimum
detectable effect
detectable
Plateau effect
maximum effect a drug can have
Dose-Response Curve
Dose-Response
Relationship between
amount of drug and
response.
High individual
variability makes it
difficult to predict
precise response to
drug.
Potency vs. Toxicity
Potency
the amount of drug necessary
to cause an effect of given intensity
Toxicity
the capacity of a drug to do damage or cause
adverse effects in the body
Toxicity & Potency
Toxicity
Q. What is a margin of safety?
A. The range in dose between the
The
amount of drug necessary to cause a
therapeutic effect and a toxic effect
therapeutic
Drug Interaction
Drug
Additive effects
Additive
Antagonistic effects
Antagonistic
Potentiative effects
Potentiative
Drug Interaction
Drug
Antagonistic (inhibitory) effects
One drug cancels or blocks effects of another
One
(cocaine vs. alcohol); 90% current cocaine
abusers also use alcohol; possibly countering
disruptive effects of alcohol (drowsiness;
slowed motor and thought) with stimulant.
slowed
Drug Interaction
Drug
Additive effects
Summation of effects of similar drugs taken
Summation
concurrently (two pain killers)
concurrently
Potentiative (synergistic) effects
Effect of a drug is enhanced by another drug or
Effect
substance (ex. Alcohol & valium).
substance
Additive effects
Additive
Potentiative (synergistic) effects
Factors affecting
Dose-Response
Dose-Response
Individual differences
Physiological (Constitution)
Physiological
Pathological (Health)
Pathological
Pharmacokinetic factors
Physiological Variables That
Modify Drug Effects
Modify
Age
Age
Gender
Gender
Pregnancy
Pregnancy
Stomach content
Liver enzyme activity
Urine acidity
Time of day
Pathological Variables That
Modify Drug Effects
Modify
Liver hepatitis longer drug action
Kidney diseases diminished excretion
Kidney
capacity
capacity
Cardiovascular diseases vulnerability to
Cardiovascular
many drugs
Pharmacokinetic Factors That
Influence Drug Effects
Influence
Pharmacokinetics study of factors that
influence the distribution and
concentration of drugs in the body.
concentration
Pharmacokinetic factors:
Administration route
Absorption rate
Distribution through body
Site of action
Biotransformation & Elimination
oral ingestion
Administration
&
Absorption
inhalation
injection
topical application
Oral ingestion
enter stomach/intestines bloodstream
target
food in the stomach/intestines may interfere
with the passage of drugs
liver may metabolize the drug very quickly
and reduce its effects (oral cocaine not very
effective)
Inhalation
drug enter body via lungs as smoke;
if cross membranes can act as fast a IV
side effect irritation of mucous
membranes lining the lungs
Injection
intravenous (IV): reaches site of injures action
quickly; vein.
intramuscular (IM): moderate speed;
can injure muscle.
subcutaneous (SC): slowest; can injure
skin.
Topical application
applied to body surfaces such as
the skin or mucous membranes (eyes,
ears, nasal lining, throat, anus,
vagina).
drugs diffuse through surface tissue
into bloodstream.
Distribution - Chemical Properties
Distribution
Ability to cross membranes
Solubility in water or fat
Solubility
Molecular size
Drug quiz- Distribution
Distribution
Q. Name the two biological barriers that
Q.
can prevent drugs from entering a body
structure
structure
A. - blood-brain barrier
Fat-soluble drugs cross BBB
- placental barrier
placental
Molecular size affects crossing
?
Drug quiz- Distribution
Distribution
?
Q. Most drugs are distributed throughout
Q.
the body in the blood. How long does it
take for a drug to circulate throughout the
body (via the bloodstream) ?
body
A. One minute
Time-Response Factors
Time-Response
Acute drug response
Immediate or short-term effects after a single
Immediate
drug dose
drug
Chronic drug response
Long-term effects after repeated doses
Long-term
Cumulative effect
the buildup of drug concentration in the body
the
due to multiple doses taken within short
intervals
intervals
Biotransformation & Elimination
Biotransformation
Biotransformation changing the chemical or
Biotransformation
pharmacological properties of a drug by metabolism
pharmacological
Metabolism chemical alteration of substances by body
Metabolism
processes
processes
Resultant products: metabolites
Liver, then kidney, most important organs for drug
Liver,
elimination
elimination
Drugs eliminated via urine, feces, perspiration and
Drugs
exhalation
exhalation
Half-life time for body to eliminate and/or metabolize
Half-life
HALF of drug dose
HALF
Regular Drug Use Activates
Adaptive Processes
The body is trying to maintain a balance and stability
of mental and physiological function
Tolerance changes causing decreased response to a
set dose of a drug
set
Dependence the physiological and psychological
changes or adaptations that occur in response to the
frequent administration of a drug
frequent
Withdrawal the effects of the bodys compensatory
Withdrawal
processes when the drug is removed;
overcompensation and severe reversal of effects of the
drug
drug
Adaptive Processes
Adaptive
Reverse tolerance
Cross-tolerance
Enhanced response to a given drug
Enhanced
dose; opposite of tolerance
dose;
Development of tolerance to one drug
Development
causes tolerance to related drugs
causes
Cross-dependence
Dependence on a drug can be relieved by
Dependence
other similar drug
other
Nature of Withdrawal Effects
Nature
Physical dependence:
characterized by the adaptive changes that occur
in the body due to the continual presence of a drug.
rebound effects (paradoxical effects) occur when
a drug has been eliminated from the body,
symptoms opposite to the direct effect of the drug.
treated using cross-dependence (alcoholism
treated with barbiturates & depressants).
Nature of Withdrawal Effects
Nature
Psychological dependence:
dependence that results because a drug produces
pleasant mental effect, drug use is rewarding, causing
euphoria, increased energy, relaxation.
even after physical withdrawal was treated, there
may still be serious psychological urge to abuse in the
form of intense cravings.
Psychological factors affecting
drug experience
drug
Mental set
Psychological and environmental factors
Psychological
(LSD use affected by pleasant vs. hostile
environment)
environment)
Placebo effects
Effects caused by suggestion and
Effects
psychological factors independent of the
pharmacological activity of the drug
pharmacological