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Chapter 5

Chapter 5

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Wilfrid Laurier University
Bruce Mc Kay

Drugs and Behaviour – Chapter 5  Sources and names of drugs o Most drugs come from plants or derived from plant substances o Names of drugs  Chemical name: name that specifies a complete chemical description of a drug  Generic name: name that specifies a particular chemical but not a particular brand  ibuprofen  Brand name: name that specifies a particular formulation and manufacturer of a drug  Tylenol  Brand names controlled by Health Canada  Categories of drugs o Psychoactive /psychotropic drug has effects on brain that results in temporary changes in thought processes, mood and behaviour  Can be used recreationally to affect a person’s consciousness, entheogen for spiritual purposes and as medication o Amphetamine, cocaine and nicotine are CNS stimulants o Barbiturates and alcohol use are CNS depressants o Morphine and codeine are analgesics (pain relievers) o LSD, ecstacy/MDMA, PCP/angel dust are hallucinogens (psychedelics) o Psychotherapeutics used to treat psychological disorders  Ritalin (treats ADHD) o Moderate doses, stimulant drugs produce wakefulness and sense of energy and well-being o More powerful stimulants can at high doses produce a manic state of excitement combined with paranoia and hallucinations o Regular use of depressant drugs can lead to withdrawal syndrome characterized by restlessness, shakiness, hallucinations and convulsions when intake of drug is reduced o Analgesics include opioid drugs that produce relaxed, dreamlike state  Cause clouding of consciousness  Withdrawal symptoms include : diarrhea, cramps, chills and profuse sweating o Psychotherapeutic drugs used for control of mental health problems  Neuroleptics can calm people experiencing psychosis  Antidepressants help people recover from seriously depressed mood states  Lithium used to control manic episodes and prevent mood swings in bipolars  Pharmacodynamics o Includes drug action and drug effects  Drug action – interaction of drug with receptors  Drug effects – resulting behavioural, cognitive and emotional changes produced following drug action o Drug effects  Drugs can’t have an effect until it is taken  To have a drug effect, drug must be brought together with a living organism  What the drug does to the body is often the reason drug is taken o Nonspecific (placebo) effect  Expectancy, experience and setting important determinants o the drug’s effect  Nonspecific effects – effects that derive from user’s unique background and perception of the world  Placebo effect  Can be produced by inactive chemical that user believes to be drug  Tests for effectiveness of new drug must be done using double-blind procedure  Neither evaluators nor participants know who’s in the control group  Placebo effects have shown in treating pain and treating psychological depression Drugs and Behaviour – Chapter 5  Nonspecific effects not caused by chemicals in drugs, but still real effects that have biological basis o Dose-response relationship  Strongest demonstration of the specific effect of drug is obtained when dose is varied and size of effect varies  Low doses, no-little effects  As dose increases, effect of drugs increase  As dose increases, increasing people show slowing of reaction time  Ataxia – staggering or inability to walk straight  As reaction time slow, ataxia appears  As dosage increases even further, they start to become comatose  Comatose – pass out and cannot be aroused  Estimating safety margin is important for animal testing before it can be tested on humans  Therapeutic index = LD50/ED50  LD50 – effective dose for half of the animals tested  ED50 – lethal dose for half of the animals tested  Lethal dose is larger than effective dose  Difference between doses is the safety margin  Acceptable level of effectiveness and lowest toxic dose  Side effects – unintended effects that accompany therapeutic effects  If number of side effects becomes too great, individual begins to suffer from them o Pharmacokinetics of drug action  Additional factors affect drug action and include pharmacokinetic factors  Pharmacokinetics can be thought of how drugs travel through body  Drug absorption – passage of drug from site of administration to circulatory system  Drug distribution – movement of drugs to and from blood and various body tissues  Drug metabolism – process by which body breaks drugs down  Drug excretion – removal of drugs  Potency  Refers to amount that must be given to obtain particular response  Smaller the amount needed, the more potent drug is  Only refers to relative effective dose (ED50 of potent drug is lower than ED50 of less potent drug)  LSD does not lead to overdose deaths, but very potent  Time-dependent factors in drug actions  Time course of drug’s effect o Time course – timing of the onset, duration and termination of a drug  Time course of drug’s action depends on many things o Administration o Rate of absorption o How it’s excreted  When maximum possible therapeutic effects has been reached, increasing dose increase side effects  Efficacy of a drug – ability to produce a desired behavioural effect  Cumulative effects – taking drugs in intervals will prolong effects  Controlled-release preparations – dosage form for drugs that are released or are activated over time o Made it so release of drugs was over a certain period of time o Mechanisms of drug action: getting the drug to the brain  A little chemistry Drugs and Behaviour – Chapter 5  Most important considerations of whether drug will enter brain is the lipid solubility o Tendency of chemical to dissolve in fat  Most psychoactive drugs dissolve in either water or lipids  Routes of administration  Oral administration o Most drugs enter body through mouth o Most complicated method to enter bloodstream o Chemical in digestive tract must withstand the actions of stomach acid and digestive enzymes and not be deactivated by food before it is absorbed  Drug molecules must get through cells lining wall of the gastrointestinal tract and into blood capillaries  The more material there is in the stomach, the more the drug dilutes and slower it will be absorbed  If taken in pill/capsule form, body must dissolve and then body can absorb it  Liquids are easier for body to absorb o Only lipid-soluble and very small water-soluble molecules are readily absorbed into bloodstream o Body will reject poisons by expelling it out of the body (vomiting)  Dangers still present even once it leaves stomach and enters bloodstream  Veins from gut go to liver first, and if liver metabolizes a large amount, very little goes into circulation  Injection o Can be injected into bloodstream o Intravenous (IV)  Directly into vein  Onset of action much more rapid than any other means of intake  Very high concentrations can be injected directly into body
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