Psychoactive Drugs
Drugs that affect the brain, changing
mood or behavior.
• 80-90% of adults in North America use
some kind of drug on a daily basis.
• The study of psychoactive drugs is
called psychopharmacology.
Depressants
• – e.g. Barbituates; benzodiazepines (e.g.
Valium); alcohol.
• Reduced anxiety; feeling of well- being and
lowered inhibitions;
• slowed pulse & breathing;
• lowered blood pressure;
• Poor concentration/ confusion or fatigue;
impaired coordination, memory or judgment;
• respiratory depression or arrest.
Stimulants
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Stimulants– e.g. ephedra;
amphetamine; MDMA;
methylphenidate (Ritalin); cocaine
nicotine; caffeine.
Increased heart rate and blood pressure.
Increased metabolism; reduced appetite;
feelings of exhilaration, increased mental
alertness;
• irritability/ anxiousness.
Opiates
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Opiate and Morphine derivatives
– e.g. opium; morphine; codeine; thebaine.
heroin, oxycodone (OxyContin)
– Pain relief; euphoria; drowsiness; respiratory
depression & arrest; nausea; confusion;
sedation (unconsciousness, coma)
Hallucinogens
– e.g. LSD; mescaline;
psilocybin.
• – Altered states of perception
& mood
• nausea; increased body
temperature; insomnia;
Peyote: source of mescaline
weakness; tremors.
• risk of chronic mental and
perception disorders.
Cannabinoids
• – e.g. hashish & marijuana
• Euphoria; slowed thinking and
reaction time;
• confusion; impaired balance and
coordination;
• Impaired memory or learning
• increased heart rate
• anxiety; panic attacks
Dependence
Psychological
Physical
Psychological Dependence
• Craving for the repeated or compulsive
use of a drug because its effects are
deemed pleasurable
• Rewarded by effects
• Positive reinforcement
• Behavior shaped by seeking pleasure
• Activating reward circuits in brain
Physical Dependence
• Dependence of the body tissues
• Revealed by life threatening
withdrawal symptoms
• Degree of dependence unknown while
drug use continues
• Magnitude of withdrawal related to
amount of previous drug use
Adaptation of cells
• Neurons alter
function during
drug use.
• Lower activity
• Greater activity
• Function differently
Withdrawal
• Stop taking drug.
• Brain rebounds.
• If brain sedated by
drug, withdrawing
brain will be
overexcited.
• If brain excited by
drug, withdrawing
brain will be
sedated.
Sedative drug
• Barbiturates or
alcohol
• Sedation while
being used.
• Excitability during
withdrawal
Stimulant drug
• Cocaine or
amphetamine
• Brain overactive
(manic) while drug
being used.
• Depression during
withdrawal
Cross Dependence
• If physically dependent
on one drug,
• Dependence transfers
to similar drugs.
• Dependent on alcohol
• Cross dependent on
barbiturates.
• Both sedatives
Managed withdrawal
• Cross dependence
important for
treatment.
• Dependent on
heroin
(illegal drug)
Withdraw person
gradually using
morphine (legal).
Psychological Dependence
• Craving for
repeated use
because of drug’s
rewarding effect.
• Learning.
• Pleasure circuits.
• Even psychological
dependence has
physical basis.
Tolerance
Level of adaptation
Tolerance
• Loss of responsiveness to
something.
• Noise; Traffic
• Drugs
• Takes more to get an effect.
• Develop tolerance to any
drug.
Mechanisms for tolerance 1
• Pharmacodynamic
• Action of drug on
neurons
• First time, neurons
most responsive
• With repeated use,
tolerance develops.
Mechanisms for tolerance 2
• Drug disposition
• Breakdown of drug by
liver.
• Liver has enzymes to
detoxify blood.
• More drug use leads to
increase in production of
enzymes.
• Increase drug use to stay
ahead of enzymes.
Initial Tolerance
• We all begin live
with certain level of
tolerance.
• Initial tolerance
• Differs from person
to person.
• High initial
tolerance is warning
sign for addiction
Developed Tolerance
• Tolerance develops to all drugs taken
repeatedly
• Doses larger than prescribed
Toxic dose
Margin of
safety
Effective dose
Initial dose
Cross Tolerance
• If tolerance develops
to one substance in a
class of drugs
• Tolerance will
transfer to other
substances in that
same class
• Barbiturates and
alcohol
Reverse Tolerance
• Liver enzymes
detoxify blood
• Break down drugs
• Liver damaged
• Tolerance lost
• More affected by
drugs