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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.

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psychoactive drugs
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.
  • – 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– 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.
  • 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)

– e.g. LSD; mescaline; psilocybin.

  • – Altered states of perception & mood
  • nausea; increased body temperature; insomnia; weakness; tremors.
  • risk of chronic mental and perception disorders.

Peyote: source of mescaline

  • – 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



psychological dependence
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
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
Adaptation of cells
  • Neurons alter function during drug use.
  • Lower activity
  • Greater activity
  • Function differently
  • 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
Sedative drug
  • Barbiturates or alcohol
  • Sedation while being used.
  • Excitability during withdrawal
stimulant drug
Stimulant drug
  • Cocaine or amphetamine
  • Brain overactive (manic) while drug being used.
  • Depression during withdrawal
cross dependence
Cross Dependence
  • If physically dependent on one drug,
  • Dependence transfers to similar drugs.
  • Dependent on alcohol
  • Cross dependent on barbiturates.
  • Both sedatives
managed withdrawal
Managed withdrawal
  • Cross dependence important for treatment.
  • Dependent on heroin

(illegal drug)

Withdraw person gradually using morphine (legal).

psychological dependence16
Psychological Dependence
  • Craving for repeated use because of drug’s rewarding effect.
  • Learning.
  • Pleasure circuits.
  • Even psychological dependence has physical basis.


Level of adaptation

  • Loss of responsiveness to something.
  • Noise; Traffic
  • Drugs
  • Takes more to get an effect.
  • Develop tolerance to any drug.
mechanisms for tolerance 1
Mechanisms for tolerance 1
  • Pharmacodynamic
  • Action of drug on neurons
  • First time, neurons most responsive
  • With repeated use, tolerance develops.
mechanisms for tolerance 2
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
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
Developed Tolerance
  • Tolerance develops to all drugs taken repeatedly
  • Doses larger than prescribed

Toxic dose

Margin of safety

Effective dose

Initial dose

cross tolerance
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
Reverse Tolerance
  • Liver enzymes detoxify blood
  • Break down drugs
  • Liver damaged
  • Tolerance lost
  • More affected by drugs