© 2006 McGraw-Hill Higher Education. All rights reserved. Chapter 5 The Actions of Drugs

© 2006 McGraw-Hill Higher Education. All rights reserved. Names Of Drugs  Chemical Name  Chemical description of the molecule  Generic Name  The legal or official name, listed in the USP  Brand Name  Trademark belongs to the manufacturer  Protected for 20 years

© 2006 McGraw-Hill Higher Education. All rights reserved. Psychoactive Drugs Stimulants Hallucinogens Marijuana Depressants Opioids Psychotherapeutics Nicotine

© 2006 McGraw-Hill Higher Education. All rights reserved. Dose-Response  Many factors can affect the way an individual responds to a drug, including:  Dose  Inherent toxicity  Potency

© 2006 McGraw-Hill Higher Education. All rights reserved. Figure 5.2 Relationship between alcohol dose and multiple response

© 2006 McGraw-Hill Higher Education. All rights reserved. Dose-Response  Additional factors:  Pharmacokinetic properties:  Rate of absorption  Manner distributed throughout the body  Rate of metabolized and eliminated  Form of the drug  Manner in which the drug is administered

© 2006 McGraw-Hill Higher Education. All rights reserved. Toxicity and Effectiveness  Assessing toxicity is calculated by:  LD-50, a statistic determined by animal testing using a wide-range of drug dosages and assessing toxicity (e.g. lethality)  Assessing the margin of safety is determined by:  Calculating the difference between the therapeutically effective dose (ED-50) and LD-50

© 2006 McGraw-Hill Higher Education. All rights reserved. Potency vs. Toxicity Potency The amount of drug necessary to cause an effect. Toxicity The capacity of a drug to do damage or cause adverse effects in the body.

© 2006 McGraw-Hill Higher Education. All rights reserved. Margin of Safety The range in dose between the amount of drug necessary to cause: a therapeutic effect, and a toxic effect

© 2006 McGraw-Hill Higher Education. All rights reserved.  Potency  Toxicity  Margin of safety

© 2006 McGraw-Hill Higher Education. All rights reserved. Figure 5.3 Possible relationship between drug concentration in the body and measured effect of the drug.

© 2006 McGraw-Hill Higher Education. All rights reserved. Forms and methods of taking drugs oral ingestion inhalation injection topical application

© 2006 McGraw-Hill Higher Education. All rights reserved. Figure 5.4 Distribution of drugs through the body

© 2006 McGraw-Hill Higher Education. All rights reserved.  Mechanisms of drug action  Effects on all neurons  Effects on specific neurotransmitter systems  Drug deactivation  Inactivation and elimination of drugs from the body  Metabolism and biotransformation  Half-life of a drug

© 2006 McGraw-Hill Higher Education. All rights reserved. Mechanisms of Tolerance and Withdrawal Symptoms   Drug Disposition Tolerance   Increased metabolism reduces the effect of the subsequent dose   pH of urine

© 2006 McGraw-Hill Higher Education. All rights reserved. Mechanisms of Tolerance and Withdrawal Symptoms  Behavioral tolerance  Reduced effect on behavior  Pharmacodynamic tolerance  Sensitivity of the neurons