Interactions, Chronic Effects & Nonspecific Factors
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Transcript Interactions, Chronic Effects & Nonspecific Factors
Interactions,
Chronic Effects, &
Nonspecific Factors
Lesson 7
Drug Interactions
Single drug
Cumulative
2 different drugs
Additive
physiological antagonism
potentiation ~
Drug Interactions
Cumulative
single drug
Additive
2 different drugs
as if adding individual drug effects
Potentiation
2 different drugs
combined effect greatly enhanced
as if multiplying individual effects ~
Single Drug
Cumulative
repeated administration
before drug completely eliminated
blood concentration
Timing
half-life important
Time course different
Subjective effects
blood concentrtions ~
Cumulative Effects
Hi
Response
Lo
Time
Multiple Drug Interactions
Physiological antagonism
drugs have opposing effects
Additive effects
drugs have same effects
Potentiation
synergistic
greater than expected by individual
drug effects ~
Physiological Antagonism
Hi
A+B
A
Drug Effect
B
Lo
Additive Effects
A+B
A
Drug Effect
B
Potentiation
A+B
Drug Effect
A
B
Chronic Use: Tolerance
After repeated use
Decreased response to the same dose
Compensatory responses
Not at a uniform rate
different for each drug effect ~
Tolerance
A
B
100
% population 50
0
0
DRUG DOSE
X
Types of Tolerance
Tachyphylaxis
rapid & transient
st 2 doses
usually between 1
NT depletion, receptors occupied
Drug Disposition Tolerance
enzyme induction ~
Types of Tolerance
Pharmacodynamic Tolerance
decreased NT synthesis
Down-regulation of receptors
Behavioral Tolerance
Volitional vs. Associative
Cross Tolerance
tolerance to 1 drug also to a 2d
e.g., alcohol & phenobarbitol ~
Chronic Use: Tolerance
Repeated use: response to same dose
Compensatory responses
Not at a uniform rate
Tachyphylaxis
Drug disposition
Pharmacodynamic
Behavioral
Cross-tolerance~
Chronic Use: Sensitization
Increased response to a repeated dose
Reverse tolerance
Cocaine & amphetamine
motor activation
Don’t know mechanism
conditioning involved
increased NT & receptor synthesis? ~
Tolerance / Sensitization
Tolerance for CNS depressants?
Sensitization for CNS stimulants?
It depends!
Alcohol: both
Cocaine: both
Chronic Cocaine in Chicks
Which curve shows sensitization?
A
B
100
% population 50
0
0
DRUG DOSE
X
Other Sources of Variability
Nonspecific factors
Organism
Psychological
Environmental
Task ~
Organism Variables
Weight
Sex & Hormonal states
Interspecies differences
Intraspecies differences
codeine analgesia
Asian
men < European
metabolism
& clearance ~
Organism Variables
Age
Disease
Nutrition
Biological rhythms ~
Other Nonspecific Variables
Psychological
Expectations
set
Placebo effects
Environmental
Setting
Task
Rate-dependent effects ~
Rate Dependency
Interaction of drug...
& baseline rate of behavior
ADHD & ritalin
stimulant to treat hyperactivity? ~
Different Effects, Same Dose
Why?
initial activity of system
Low activity in system
drug increases effects
High activity in system
drug may decrease effects ~
drug dose
max
drug dose
x
Behavior
x
x
x
min
lo
Drug amount (dose)
Difference in baseline activity.
hi
Should you take a drug?
Rational judgment process
But often not
Many factors involved
Learning:
Classical & Operant Conditioning ~