The document discusses several key concepts related to how drugs work in the body including: - Intended effects are the reasons for using a drug while unintended effects are side effects. Common side effects include nausea, changes in alertness, and dependence. - A drug's effects depend on factors like dose, tolerance, potency, route of administration, rate of absorption, distribution and metabolism. Higher doses can produce therapeutic or toxic effects. - Drug interactions can be additive, antagonistic, or synergistic. Pharmacokinetic factors like metabolism and elimination influence drug effects.

1. How and Why Drugs Work Chapter 5

2. Intended and Unintended Effects of Drugs 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.

3. Common Side Effects of Drugs Nausea or vomiting Changes in mental alertness Dependence Withdrawal Allergic reactions Changes in cardiovascular activity © fred goldstein/ShutterStock, Inc.

4. Common Side Effects of Drugs (continued)

5. Dose-Response Many factors can affect the way an individual responds to a drug, including the following: Dose Tolerance Potency

6. Dose-Response (continued) Additional factors Pharmacokinetic properties Rate of absorption Manner distributed throughout the body Rate metabolized and eliminated Form of the drug Manner in which the drug is administrated

7. Dose-Response Curve

8. Margin of Safety The range in dose between the amount of drug necessary to cause a therapeutic effect and a toxic effect

9. Potency vs. Toxicity Toxicity the capacity of a drug to do damage or cause adverse effects in the body Potency the amount of drug necessary to cause an effect

10. Drug Interaction Additive effects Summation of effects of drugs taken concurrently Antagonistic (inhibitory) effects One drug cancels or blocks effects of another Potentiative (synergistic) effects Effect of a drug is enhanced by another drug or substance

11. Pharmacokinetic Factors That Influence Drug Effects Administration Absorption Distribution Activation Biotransformation and elimination

12. Forms and Methods of Taking Drugs oral ingestion inhalation injection topical application © Oscar Knott/FogStock/Alamy Images

13. Distribution Most drugs are distributed throughout the body in the blood. It takes approximately 1 minute for a drug to circulate throughout the body after it enters the bloodstream. Drugs have different patterns of distribution depending on their chemical properties.

14. Required Doses for Effects Threshold dose —the minimum amount of a drug necessary to have an effect Plateau effect —the maximum effect a drug can have regardless of the dose Cumulative effect —the buildup of drug concentration in the body due to multiple doses taken within short intervals

15. Time-Response Factors The closer a drug is placed to the target area, the faster the onset of action. Acute drug response Immediate or short-term effects after a single drug dose Chronic drug response Long-term effects after a single dose

16. Biotransformation Biotransformation —the process of changing the chemical or pharmacological properties of a drug by metabolism. The liver is the major organ that metabolizes drugs in the body. The kidney is the next most important organ for drug elimination.

17. Physiological Variables That Modify Drug Effects Age Gender Pregnancy © Pixtal/SuperStock

18. Adaptive Processes Tolerance – changes causing decreased response to a set dose of a drug Dependence – the physiological and psychological changes or adaptations that occur in response to the frequent administration of a drug Withdrawal

19. Adaptive Processes (continued)

20. Tolerance Reverse tolerance (sensitization) Enhanced response to a given drug dose; opposite of tolerance Cross-tolerance Development of tolerance to one drug causes tolerance to related drugs

21. Drug Dependence Physical dependence Psychological dependence

22. Psychological Factors Affecting Drug Effect Individual’s mental set Placebo effects

23. Addiction and Abuse The term addiction has many meanings. It is often used interchangeably with dependence, either physiological or psychological in nature; other times, it is used synonymously with the term drug abuse.

24. Addiction and Abuse (continued) Factors affecting variability in dependence Hereditary factors Drug craving

25. Addiction and Abuse (continued) Other factors contributing to drug use patterns Positive versus negative effects of drug Peer pressure Home, school, work environment Mental state