Principles of Drug Action and
Interaction
Jane Bordner, RN, BSN
Nursing Instructor
HACC
N100
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/sec02/ch011/
ch011a.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
iscoverbio4/animations/main.aspx?chno=ch0
6a01
Pinocytosis
Variables Affecting Rate of
Absorption
• Route of
administration
• Solubility of
drug
• First-pass effect
• Surface area
•
•
•
•
Rate of blood flow
pH
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
–
blood flow =
absorption
Other Variables
• pH
– pH of gastric contents
– pH 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
pH
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
Factors Influencing Drug Response
•
•
•
•
•
•
Age
Weight
Gender/Genetics
Disease/Illness
Route of Administration
Psychological Factors
Infants and Children
• Immature organ systems
– Liver and kidneys
• Smaller doses
• Some drug too toxic