RSPT 1213 – Respiratory Care Pharmacology
Principles of Pharmacology
Lecture Notes
I. The entire course of a drug’s action from dose to effect is seen in three phases:
a. Drug Administration
b. Pharmacokinetic phase
c. Pharmacodynamic phase
II. Systemic vs. local effect
a. Systemic – whole body, target of drug is not local; possible side effects
b. Local – limited to area of treatment
III. Drug Administration Phase
a. Method by which a drug dose is made available to the body
b. Two key topics:
 Drug dosage form – physical state of a drug along with other nondrug
components (tablets, capsules, injectable solution)
Route of administration – portal of entry for the drug into the body
(oral, inhalation, injection)
IV. Routes of Administration
a. Enteral – intended for drugs for absorption anywhere along the GI tract
b. Parenteral – any route other than enteral (injection)
IV
IM
SC
c. Transdermal – application to skin; long-term
d. Inhalation – can be intended for systemic or local effect
Systemic – anesthesia gases
Local – respiratory drugs
General rationale for aerosolized drugs is to target organ with reduced
or minimal body exposure to the drug with intention to reduce
prevalence or severity of possible side effects
V. Pharmacokinetic phase – the time course and disposition of a drug in the body based on
its:
a. Absorption – When a drug is administered there are barriers to drug absorption
In the lower respiratory tract the mucosal barrier has 5 elements:
1. Airway surface liquid
2. Epithelial cells
3. Basement membrane
4. Interstitium
5. Capillary vasculature
A drug must be sufficiently water soluble (aqueous diffusion) to reach a
cell (lipid) membrane [epithelial cells] and sufficiently lipid soluble to
diffuse across the cell barrier
b. Distribution – the process by which a drug is transported to the site of action,
eliminate or stored. Determines concentration in the system
Partially dependant on rate/extent of absorption vs. rate of elimination
for a certain dose
Also determined by volume of drug given
Inhaled can be swallowed (local vs. systemic effect)
c. Metabolism – drug molecules are metabolized in the liver and placed in the
system via inferior vena cava
d. Elimination – kidneys are the primary site of excretion of a drug
Pharmacokinetics describes what the body does to a drug
VI. Drug Half-life: The half-life of a drug is the time required for plasma concentration of a
drug to decrease by one-half
Indicates how quickly a drug can accumulate and reach steady level
Drugs with a short half life reach steady states quickly  must be given
more often
Drugs with a long half life take longer  don’t have to be given that
often
VII. Pharmacodynamics – mechanisms of drug action where a drug molecule causes its effect
on the body.
a. Most drugs have affect by binding to protein targets and inducing physiological
changes affects tissues and organs
Protein targets include: receptors, enzymes, ion channels and carrier
molecules
b. Receptors – once a drug reaches the target organ and before it is metabolized
& eliminated, it meets the receptor which creates a chemical action or
response to the drug
Pharmacodynamics describe what the drugs does to the body
VIII. Receptor Agonists vs. Antagonists
a. Agonist – drug or chemical that binds to a corresponding receptor (affinity) and
intitiates a chemical effect/response (efficacy)
b. Antagonist – drug or chemical that is able to bind to a receptor (affinity) that
causes no effect (zero efficacy)
IX. Dose-Response relationships
a. The response of a drug is proportional to the drug concentration
b. Drug effect increases to a maximal point
Maximal effect – greatest response that can be produced by a drug – any
dose above will provide no further response
Potency – refers to concentration or dose producing 50% of drug
maximal response.
c. Therapeutic index – represents the safety margin of a drug
It is the ratio of the dose that is toxic to 50% of test subjects to the
dose that provides relief to 50% of the subjects
The smaller the TI the greater the possibility of crossing from
therapeutic effect to toxic effect.