Chapter 2 Principles of Drug Action and Drug Interactions Jeanelle F. Jimenez RN, BSN, CCRN Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.

Objectives Identify five basic principles of drug action. List three categories of drug administration and state the routes of administration for each category Describe nursing interventions that can enhance drug absorption Differentiate between general and selective types of drug distribution mechanisms Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.

Objectives (cont’d) Explain nursing assessments necessary to evaluate potential problems associated with the absorption of medications Name the process that inactivates drugs Identify the meaning and significance to the nurse of the term half-life when used in relation to drug therapy Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.

Objectives Compare and contrast the following terms used in relationship to medications Desired action Side effects Adverse effects Allergic reactions Idiosyncratic reactions State the mechanisms whereby drug interactions may occur Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.

Objectives (cont’d) Differentiate among the following terms used in relationship to medications Additive effect Synergistic effect Antagonistic effect Displacement Interference Incompatibility Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.

Principles of Drug Action and Drug Interactions Basic principles An understanding of the human body’s processes is important to grasp drug actions and drug interactions in the body A B C D Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.

5 Stages of Drug Administration Liberation Absorption Distribution Metabolism Excretion Mosby items and derived items © 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.

Liberation The release of a drug from the dosage form (liberation) and dissolved in body fluids before it can be absorbed into body tissues Parenteral administration Percutaneous administration Mosby items and derived items © 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.

Drug Stages After Administration ADME Absorption – depends on route of administration Distribution – depends on circulation to be transported throughout body Metabolism – depends on enzyme systems Excretion – depends on GI tract and kidneys Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.

Half-life of Drugs Factors modifying the quantity of drug reaching a site of action after a single oral dose Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.

Factors Affecting Drug Response Age Body weight Metabolic rate Illness Psychological aspects Tolerance of the medication Dependence developed from the medication Cumulative effect of the medication Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.

Responses to Drugs Desired effect Side effects Adverse effects Idiosyncratic effects Allergic reactions Teratogen Carcinogen Mosby items and derived items © 2010, 2007, 2004 by Mosby, Inc., an affiliate of Elsevier Inc.