General Properties of Drugs

1
General Properties of Drugs
Source Essentials of Paramedic Care
2
Objectives

• Pharmaceutical phase
• Pharmacokinetic phase
• Absorption
• Distribution
• Biotransformation
• Excretion
• Pharmacodynamics
• Considerations

3
Pharmaceutical Phase

• Science of dispensing drugs

4
Pharmacokinetics

• Study of how the body handles a drug over a
  period of time
• 4 Components
• Absorption
• Distribution
• Biotransformation
• Excretion / Elimination

5
Review

• Diffusion
• Osmosis
• Facilitated diffusion (carrier mediated)
• Active transport

6
Drug Absorption

• From point of entry to general circulation
• Factors that affect absorption
• Nature of cell membrane
• Blood flow to target site
• Solubility of drug
• pH of drug environment
• Drug concentration
• Form of drug dosage (coating)

7
The pH of the Drug Environment

• Form of drug in solution
• Ionized (charged) Lipid insoluble
• Nonionized (uncharged) Lipid soluble readily
  diffuses

ASA
Non-ionized therefore readily diffuses Across
membranes into circulation.
8
Drug Concentration

• Loading Dose
• Maintenance Dose

9
Drug Distribution

• Transport of a drug through blood stream to
  target
• Key Points
• Drug reservoirs
• Barriers to distribution

10
Drug Reservoirs

• Protein Binding
• Drug bound to plasma may dissociate when free
  drug is excreted
• Fat Tissue / Bone Storage

11
Drug Barriers

• Placental Barrier
• Blood Brain Barrier

12
Biotransformation

• Metabolism
• Break down detoxify
• First pass metabolism
• Enter GI tract travel to liver before entering
  circulation

13
Excretion

• Elimination of toxic or inactive metabolites
• Kidneys
• Passive glomerular filtration
• Active tubular secretion
• Partial re-absorption

14
Excretion

• Intestines (Bile)
• Lungs
• Sweat Salivary Glands
• Mammary Glands

15
Biological Half Life

• Time to metabolize ½ the total amount of drug in
  body
• Drug considered completely removed from body
  after five half lives

16
Pharmacodynamics

• How the drug ACTS on body
• Affinity
• Efficacy
• Agonist
• Antagonist
• Therapeutic Index LD 50
• ED 50

17
Factors Affecting Drugs

• Age
• Body Mass
• Gender
• Environment
• Time (Presence of food)
• Pathologies
• Genetics
• Psychological

18
Pregnancy

• Cat A Controlled tests on women with no risks
• Cat B Animal tests no problem but
• No Human study info
• Cat C Studies in women animals not
  available
• Cat D Positive evidence of human fetal risk,
  but benefits may be acceptable despite risk
• Cat X Studies in animal humans show fetal
  abnormalities

19
Terminology

• Teratogenic drug Medication that may deform or
  kill the fetus

20
Review

• Pharmaceutical phase
• Pharmacokinetic phase
• Absorption
• Distribution
• Biotransformation
• Excretion
• Pharmacodynamics
• Considerations