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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