Principles of Drug Action and Interaction Jane Bordner

Principles of Drug Action and Interaction Jane Bordner, RN, BSN Nursing Instructor HACC N 100 Spring 2015

Drug Names • Chemical name/Scientific name – Exact chemical make up of drug

Drug Names • Generic – Name as designated by US Adopted Names Council of Federal Government (FDA) – Based on chemical compound of drug – Not capitalized – Example = ibuprofen

Drug Names • Trade – Brand name given to drug by pharmacological company that developed and patented drug – Patent by US patent office and approved by FDA – Always capitalized – Example = Motrin and Advil

Sources of New Drug Information • • • Nursing Drug Reference Books Physician’s Desk Reference (PDR) Package inserts National Formulary On-line resource: – http: //www. nlm. nih. gov/medlineplus/dr uginformation. html – http: //www. drugguide. com/ddo/ub

Drug Categories • • Prescription Nonprescription (OTC) Controlled substances Herbal and dietary suppliments

Controlled Substance Act • 5 Schedules or levels of drugs – Classification related to potential for abuse and severity of dependence – Schedule 1 has highest potential for abuse – Schedule 5 lowest

Herbal and Dietary Suppliments • 80% of world’s population relies on herbs • Not without adverse effects • Can be toxic especially in combination with another medication

Legal Regulations and Standards R/T Medication Adm. • The Controlled Substance Act designates categories or schedules, that classify controlled drugs according to their potential for abuse. • Department of State and State Board of Nursing delineates the scope of practice for nurses in each state.

State Board of Nursing • Board that is charged with regulating nursing practice • Very fluid • Scope of practice may be different in each state

Practical Nurse and Medication Administration • May administer PO, IM and SQ • May perform intradermal skin testing • May administer premixed IV drugs • May monitor IV fluids

Practical Nurse and Medication Administration • MAY NOT administer certain IV medications – Antineoplastic agents – Blood and blood products – Total Parenteral Nutrition – IV push medications – Titrated medications

Drug Classifications • Drugs classified by – Body system – Therapeutic use – Clinical indication – Physiologic or chemical action

Phases of Pharmacology • Pharmaceutic • Pharmacokinetic • Pharmacodynamic

I. Pharmaceutic Phase • • • Dissolution of drug How drug becomes soluble Drug must be soluble to be absorbed Dependent on dosage form Occurs in GI tract Enteric coated/time-release meds

II. Pharmacokinetic • Movement of drug through body – Includes: • Absorption • Distribution • Metabolism • Excretion • http: //www. merck. com/mmhe/sec 02/ch 011/ ch 011 a. html

Absorption • Drug made available for use in body • How drug is transferred from site of entry into body fluids – Route of administration – Solubility of drug – Blood flow in tissue

Absorption • Active transport • Passive transport • Pinocytosis

• http: //www. wwnorton. com/college/biology/d iscoverbio 4/animations/main. aspx? chno=ch 0 6 a 01

Pinocytosis

Variables Affecting Rate of Absorption • Route of administration • Solubility of drug • First-pass effect • Surface area • • Rate of blood flow p. H GI motility Drug interactions

Route of Administration • Enteral • Parenteral • Percutaneous

Solubility of Drug • Dissolve in water or fat • Blood brain barrier General body cells Brain Cells

First Pass Effect • Liver changes drugs before they pass into general circulation • PO dose vs. IV dose

Surface Area • Related to site of administration • How much medication is available to site of absorption? • Oral medications = mucosal lining of small intestine

Blood Flow • Absorption depends on blood flow – blood flow = absorption

Other Variables • p. H – p. H of gastric contents – p. H of blood • GI motility – Enteral route only – Fat content of food • Drug interactions

Distribution • How drug is carried from site of absorption to site of action • Drug storage

Factors That Influence Distribution • Blood flow • Drug Solubility • Protein binding – Plasma carrier proteins – Storage tissue proteins – Receptor proteins • Inactive drug • Active drug

Plasma Carrier Proteins

Storage Tissue Proteins

Receptor Proteins

Receptor Protein Storage Tissue Protein Plasma Carrier Protein

Metabolism/Biotranformation • Process by which body changes drugs • Metabolites • Liver is primary site for most drugs

Excretion • Metabolites and/or active drug is removed from body • Primary routes of excretion

Half-life • Time required for 50% of a drug to be eliminated from body • Determine dosage regimen of drug

Half-Life # 4 hour intervals 0 Time in hours Dosage in mg. 0 1 4 2 8 3 12 4 16

Half-Life # 6 hour intervals 0 Time in hours 1 6 2 12 3 18 4 24 0 Dosage in mg.

Half-Life

Onset, Peak, and Duration • ONSET – Drug is sufficiently absorbed to reach effective level • PEAK – Maximum blood level for dose • DURATION – Length of time drug concentration is sufficient to produce a therapeutic response

Peak Duration Onset

III. Pharmacodynamic Phase • Mechanism by which drug produces biochemical or physiological changes • Drug action and effect on body tissues • Occurs with Pharmacokinetics

Drug Action • Interaction at cellular level between a drug and cellular components • Therapeutic action – Target sites • Secondary actions

Alteration in Cellular Function • Receptor-mediated • Mimic or block regular cell function • Number of receptors influences drug effect

Receptor-Mediated

Alteration in Cellular Environment • Drug changes cellular environment – Physically and Chemically • • • Osmotic pressure Drug – Enzyme Antimetabolites Absorption/Chelating Agents p. H Changes in Cell Membranes

Drug Effect • Response resulting from a drug action • Example: Insulin – Drug Action = Transport of glucose across the cell membrane – Drug Effect = Lowering of blood glucose level