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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 . Depressants. – e.g. Barbituates; benzodiazepines (e.g. Valium); alcohol.

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Psychoactive Drugs

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  1. 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.

  2. 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.

  3. Stimulants • 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.

  4. Opiates • 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)

  5. Hallucinogens – 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

  6. 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

  7. Dependence Psychological Physical

  8. 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

  9. 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

  10. Adaptation of cells • Neurons alter function during drug use. • Lower activity • Greater activity • Function differently

  11. 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.

  12. Sedative drug • Barbiturates or alcohol • Sedation while being used. • Excitability during withdrawal

  13. Stimulant drug • Cocaine or amphetamine • Brain overactive (manic) while drug being used. • Depression during withdrawal

  14. Cross Dependence • If physically dependent on one drug, • Dependence transfers to similar drugs. • Dependent on alcohol • Cross dependent on barbiturates. • Both sedatives

  15. Managed withdrawal • Cross dependence important for treatment. • Dependent on heroin (illegal drug) Withdraw person gradually using morphine (legal).

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

  17. Tolerance Level of adaptation

  18. Tolerance • Loss of responsiveness to something. • Noise; Traffic • Drugs • Takes more to get an effect. • Develop tolerance to any drug.

  19. Mechanisms for tolerance 1 • Pharmacodynamic • Action of drug on neurons • First time, neurons most responsive • With repeated use, tolerance develops.

  20. 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.

  21. 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

  22. Developed Tolerance • Tolerance develops to all drugs taken repeatedly • Doses larger than prescribed Toxic dose Margin of safety Effective dose Initial dose

  23. 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

  24. Reverse Tolerance • Liver enzymes detoxify blood • Break down drugs • Liver damaged • Tolerance lost • More affected by drugs

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