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Pharmacology For The
Physical Therapy Clinician
Basic Principles
Pharmacology
can be broadly
defined as the science dealing
with interactions between living
systems and molecules
Throughout
the ages, drugs have
been produced using natural
plant and animal products by
native people. This practice has
been part of every culture and
society in every corner of the
world.
Some Examples…….
Hollyhock
Tea - made from the
leaf and root of the Hollyhock
plant.
Used For : sore throats, duodenal
ulcers, GI tract infections
Echinacea
- the roots, seed heads
& petals can be used to make an
Echinacea tincture and salve
Uses : stimulates immune
defense, speeds healing, limits
edema & swelling.
Jojoba
- the beans and the leaves
are used to make a variety of oil,
soap & shampoo products.
Uses : Soaps, shampoos, oil
lubricants - often used for a
remedy for asthma, dandruff,
and as an anti-inflammatory
Advantages Of Synthetic
Drugs
Improved
purity
Improved action due to an
altered chemical structure
Longer biological half-life
Improved fat solubility
Greater
drug concentration
Longer shelf life
Preserve the environment
Less costly to produce
Drug Interactions With A
Biological System
Pharmacodynamic
Interactions
Pharmacokinetic Interactions
Pharmacodyamic
Interactions
The mechanism of action - the
the drug works on the body
Pharmacokinetic
Interactions
The way in which the body absorbs,
distributes and eliminates the drug
Drug Nomenclature
Chemical
Name
The chemical name describes the
chemical structure of a drug.
Used by pharmacists &
researchers all over the world
Examples…….
Tylenol
(Acetaminophen)
N-acetyl-para-aminophenol
Phenobarbitol
5,5-phenylethylbarbituric acid
Generic
Name
It is generally derived from the
chemical name but is shorter
It is also known as the official or
non-proprietary name
Examples…….
Dextromethorphan
Dextromethorphan is the generic
name for the drug with the chemical
name of :
d-3-methoxy-N-methylmorphinan
Dantrolene
Sodium
Dantrolene is the generic name for
the drug with the chemical name of :
1-[[[5-(4-nitrophenol)-2furanyl]methylene]amino]-2-4imidazolidinedione
Trade
Name
This is the name the manufacturer
gives to the drug that distinguishes
it from the same drug made by
other drug companies
Examples…….
Flecanide Acetate
is the generic
name for a drug with the trade
name of :
Tambocor
Digoxin
is the generic name for
the drug with the trade name of :
Lanoxin
Bepridil
HCl is the generic name
for a drug with the trade name of :
Vascor
The
FDA catalogs the drug by its
generic name
The manufacturer catalogs the drug
by its trade name
The research pharmaceutical chemists
know the drug by its chemical name
Routes of Administration
Enteral
Routes
Parenteral Routes
Enteral Routes
Drugs
that are administered
through the alimentary canal via
the sublingual, oral or rectal
routes
Advantages Of The Enteral
Route
It
is not invasive
Ease of drug administration
The mouth and the GI tract
have a rich blood supply for
pancorporeal dispersal of the
medication
The
enteral route avoids large
fluctuations in drug delivery
Patients are familiar with the
oral delivery route
The GI tract has a massive
surface area for absorption
Disadvantages of the
Enteral Route
Drugs
must be lipid soluble
Drugs can be irritating to the
mucosa of the mouth and the gut
First
Pass Effect
The presence of diseases like
Crohn’s Disease is a problem
pH of the GI tract
Parenteral Routes
Drugs
administered through nonalimentary pathways such as :
inhalation, intravenous, intraarterial, subcutaneous,
intramuscular, intrathecal, ocular,
topical, and transdermal
Advantages of Parenteral
Routes
Fast
delivery of the medications (IV,
inhalation, and intra-arterial routes)
Efficient maintenance of therapeutic
ranges (IV and intra-arterial routes)
Ease
of self administration (topical,
inhalation, rectal, & subcutaneous
routes)
Can give large quantities of
medication (IV, intra-arterial)
First Pass Effect
When
an enterally administered
drug passes for the first time
from the gut into the hepatic
portal system and enters the
liver, it can undergo First Pass
Effect
During
First Pass Effect, a certain
percentage of the drug is changed
from the original mother compound
into some intermediate metabolite.
All of the drug then passes out into
the systemic circulation as 1) the
intact drug plus its 2) changed
intermediates.
For
some drugs, like sublingual
nitroglycerin, if it were swallowed, it
would be totally inactivated by the
liver. So, its first pass effect is
complete or 100%
For
other drugs that are not as easily
cleaved, the First Pass Effect might
only be 10%. This means that 90%
of the mother compound enters the
systemic circulation with only 10%
that has been changed into an
intermediate.
The
intermediate compounds after
First Pass Effect may be biologically
inactive or they might be extremely
active in the body. Many cancer
drugs are designed to have
intermediates that are just as
biologically active against the tumor
as the mother compound.
Some
medications are designed to be
inactive in the pill form. Once these
medications pass into the liver (First
Pass Effect) they are cleaved into
their biologically active intermediate
forms. In the pill form, these drugs
are called Pre-Drugs.
Bioavailability
Bioavailability
is defined as the
amount of drug that actually makes
it to the intended downstream target.
Bioavailability is influenced by a
number of factors.
Factors Influencing
Bioavailability
First
Pass Effect
Route of administration
Lipid solubility of the drug
Blood flow at the administration
site
Blood
flow at the intended target
organ or site
Absorptivity of the gut
How easily the drug is changed or
metabolized
Drug Elimination
The
liver and the kidneys are the
major detoxification organs in
the body
The blood, muscles and the lungs
are secondary areas where
detoxification occurs
Biotransformation
The
body detoxifies itself through
inducing chemical changes in the
drugs that have been ingested
The body biochemically alters the
drugs through biochemical processes
like hydrolysis, oxidation, reduction,
conjugation
Enzyme Induction
Long
term use of medications
stimulates enzymatic pathways
in the body to more vigorously
breakdown the medication into
intermediates that can be easily
excreted in the feces or urine
There are many stimuli that cause enzyme
induction to be turned on such as :
tobacco use
alcohol use
drug abuse
environmental wastes and toxins
Why Do Humans Respond
Differently To Medications ?
Genetic
Factors
Diet, Age, & Adiposity
Alcohol & Tobacco Use
Disease State