lecture_Ch05[1] - Drugs and Behavior Drugs How and Why...

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Unformatted text preview: Drugs and Behavior Drugs How and Why Drugs Work PSY 291 PSY Intended and Unintended Effects of Drugs Intended Intended vs. Unintended Drug Effects Intended responses: reason for using the drug Unintended responses: side effects The main distinction between intended responses and side effects depends on the therapeutic objective. 5 Common side effects Common Nausea or vomiting Nausea Changes in mental alertness Changes Dependence Dependence Allergic reactions Allergic Changes in cardiovascular activity Common side effects of drugs Common Factors Affecting Individual’s Response Individual’s Drug concentration Dose-response Threshold / Plateau Potency Potency Toxicity Toxicity Dose-Response Curve Dose-Response Relationship between amount of drug and response. High individual variability makes it difficult to predict precise response to drug. Drug Concentration Drug Threshold dose Threshold minimum amount of a drug necessary to have an minimum detectable effect detectable Plateau effect maximum effect a drug can have Dose-Response Curve Dose-Response Relationship between amount of drug and response. High individual variability makes it difficult to predict precise response to drug. Potency vs. Toxicity Potency the amount of drug necessary to cause an effect of given intensity Toxicity the capacity of a drug to do damage or cause adverse effects in the body Toxicity & Potency Toxicity Q. What is a “margin of safety”? A. The range in dose between the The amount of drug necessary to cause a therapeutic effect and a toxic effect therapeutic Drug Interaction Drug Additive effects Additive Antagonistic effects Antagonistic Potentiative effects Potentiative Drug Interaction Drug Antagonistic (inhibitory) effects One drug cancels or blocks effects of another One (cocaine vs. alcohol); 90% current cocaine abusers also use alcohol; possibly countering disruptive effects of alcohol (drowsiness; slowed motor and thought) with stimulant. slowed Drug Interaction Drug Additive effects Summation of effects of similar drugs taken Summation concurrently (two pain killers) concurrently Potentiative (synergistic) effects Effect of a drug is enhanced by another drug or Effect substance (ex. Alcohol & valium). substance Additive effects Additive Potentiative (synergistic) effects Factors affecting Dose-Response Dose-Response Individual differences Physiological (Constitution) Physiological Pathological (Health) Pathological Pharmacokinetic factors Physiological Variables That Modify Drug Effects Modify Age Age Gender Gender Pregnancy Pregnancy Stomach content Liver enzyme activity Urine acidity Time of day Pathological Variables That Modify Drug Effects Modify Liver hepatitis – longer drug action Kidney diseases – diminished excretion Kidney capacity capacity Cardiovascular diseases – vulnerability to Cardiovascular many drugs Pharmacokinetic Factors That Influence Drug Effects Influence Pharmacokinetics – study of factors that influence the distribution and concentration of drugs in the body. concentration Pharmacokinetic factors: Administration route Absorption rate Distribution through body Site of action Biotransformation & Elimination oral ingestion Administration & Absorption inhalation injection topical application Oral ingestion enter stomach/intestines bloodstream target food in the stomach/intestines may interfere with the passage of drugs liver may metabolize the drug very quickly and reduce its effects (oral cocaine not very effective) Inhalation drug enter body via lungs as smoke; if cross membranes can act as fast a IV side effect – irritation of mucous membranes lining the lungs Injection intravenous (IV): reaches site of action quickly; injures vein. intramuscular (IM): moderate speed; can injure muscle. subcutaneous (SC): slowest; can injure skin. Topical application applied to body surfaces such as the skin or mucous membranes (eyes, ears, nasal lining, throat, anus, vagina). drugs diffuse through surface tissue into bloodstream. Distribution - Chemical Properties Distribution Ability to cross membranes Solubility in water or fat Solubility Molecular size Drug quiz- Distribution Distribution Q. Name the two biological barriers that Q. can prevent drugs from entering a body structure structure A. - blood-brain barrier Fat-soluble drugs cross BBB - placental barrier placental Molecular size affects crossing ? Drug quiz- Distribution Distribution ? Q. Most drugs are distributed throughout Q. the body in the blood. How long does it take for a drug to circulate throughout the body (via the bloodstream) ? body A. One minute Time-Response Factors Time-Response Acute drug response Immediate or short-term effects after a single Immediate drug dose drug Chronic drug response Long-term effects after repeated doses Long-term Cumulative effect the buildup of drug concentration in the body the due to multiple doses taken within short intervals intervals Biotransformation & Elimination Biotransformation Biotransformation – changing the chemical or Biotransformation pharmacological properties of a drug by metabolism pharmacological Metabolism – chemical alteration of substances by body Metabolism processes processes Resultant products: metabolites Liver, then kidney, most important organs for drug Liver, elimination elimination Drugs eliminated via urine, feces, perspiration and Drugs exhalation exhalation Half-life – time for body to eliminate and/or metabolize Half-life HALF of drug dose HALF Regular Drug Use Activates Adaptive Processes The body is trying to maintain a balance and stability of mental and physiological function Tolerance – changes causing decreased response to a set dose of a drug set Dependence – the physiological and psychological changes or adaptations that occur in response to the frequent administration of a drug frequent Withdrawal – the effects of the body’s compensatory Withdrawal processes when the drug is removed; overcompensation and severe reversal of effects of the drug drug Adaptive Processes Adaptive Reverse tolerance Cross-tolerance Enhanced response to a given drug Enhanced dose; opposite of tolerance dose; Development of tolerance to one drug Development causes tolerance to related drugs causes Cross-dependence Dependence on a drug can be relieved by Dependence other similar drug other Nature of Withdrawal Effects Nature Physical dependence: characterized by the adaptive changes that occur in the body due to the continual presence of a drug. rebound effects (paradoxical effects) occur when a drug has been eliminated from the body, symptoms opposite to the direct effect of the drug. treated using cross-dependence (alcoholism treated with barbiturates & depressants). Nature of Withdrawal Effects Nature Psychological dependence: dependence that results because a drug produces pleasant mental effect, drug use is rewarding, causing euphoria, increased energy, relaxation. even after physical withdrawal was treated, there may still be serious psychological urge to abuse in the form of intense cravings. Psychological factors affecting drug experience drug Mental set Psychological and environmental factors Psychological (LSD use affected by pleasant vs. hostile environment) environment) Placebo effects Effects caused by suggestion and Effects psychological factors independent of the pharmacological activity of the drug pharmacological ...
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