Transcript What is a drug?

Basic Pharmacology
What is a drug?
- any chemical agent which
effects any biological process
What is pharmacology ?
- the
study of how drugs
effect biological systems
Introduction

A. Physical Nature of Drugs
 Solid drugs -> oral route
aspirin or atropine
 Liquid drugs -> oral route, IM, SC
nicotine or ethanol
 Gaseous drugs -> inhalation
nitrous oxide, halothane, amylnitrite
Many drugs are weak acids or bases
pH differences in the body may alter the degree of
ionization of drug

What is Pharmacology ?
Pharmacokinetics
Pharmacodynamics
What the body does to drug
What the drug does to body
Pharmacology
Pharmacotherapeutics
The study of the use of drugs
Pharmacocognosy
Identifying crude materials as drugs
Toxicology
Pharmacokinetics
What the body does to the
drug
- Absorption
- Distribution
- Metabolism (Biotransformation)
- Excretion
Half-life (t1/2)
- the time required for the plasma
concentration of a drug to be reduced by 50
Pharmacodynamics
What the drug does to the body
- Drug receptors
- Effects of drug
- Responses to drugs
- Toxicity and adverse effects of
drugs
Sources of Drugs
Pharmacocognosy
Animals
Plants
Minerals
Synthetic
Microbes
Many of these old sources are
still in use today
 Foxglove
plant
 Meadow
flower
Colchicum autumnale
 Beef
or pork pancreas
 Digitalis
comes from the
foxglove plant and is used
in the treatment of CHF
 Colchicine
is the drug of
choice for treatment of
gout
 Insulin
is used today to
treat diabetes and is
derived from the pancreas
of beef or pork or may be
synthetically produced as
Drugs Derived from Plants
 Ephedrine
is present in the leaves of a bushy
shrub (species name Ephedra), which, when
burned were used by the ancient Chinese to treat
respiratory ailments. Today, it is a
bronchodilator.
 Many estrogen hormone replacement therapy
drugs are derived from yams.
 The belladonna plant – source of atropine, which
is still used to dilate the pupils.
DRUG CLASSIFICATION
- Based on the chemical structure
- Based on the main effect (e.g.
analgesics).
- Based on the therapeutic use (e.g.
antipsychotic).
-Based on mechanism of action (e.g.
serotonin agonist).
Drug Nomenclature
mical name
- *Generic name
- Trade
Chemical Name: 2-(4-isobutylphenyl)-propionic acid
Generic Name: ibuprofen
Trade Names: Advil, Aches-N-Pain,
Brufen,
Emodin, Haltran, Medipren,
Midol 200, Motrin, Nuprin,
Rufen, Trendar, Wal-Profen
*preclinical nomenclature =
company abbrev-123456 (e.g. WAY-100635, MK-869)
Routes of Administration

Critical to efficacy
 Rapidity
of onset
 Duration of effects
 Magnitude of effects

Systemic administration
 Drug
into circulatory system via ...
 Enteral routes
 Parenteral routes
 Drug effects throughout body ~
Routes of Drug
Administration

Enteral
 within


Oral (PO), rectal, sublingual
Parenteral
 Not


or by way of the GI tract
within the alimentary canal
Inhalation, IM, SC, IP, topical
Central


Into the brain or spinal cord
Intrathecal, ICV
Routes of Drug Administration
common abbreviations…
PO = per os = oral
IV = intravenous = into the vein
IM = intramuscular = into the muscle
SC = subcutaneous = between the skin and muscle
IP = intraperitoneal = within the peritoneal cavity
icv = intracerebroventricular =
directly into the ventricle of the brain
Oral

Per Os (PO)

by mouth
 absorption
across
membrane in GI
 most common
 most variable
 1st pass metabolism
Cooperation required
 Can recall ~

Oral

Sublingual
 Absorption:


mucous membrane
salivary glands
 e.g.,
nitroglycerin,
buprenorphine

Chewing
 absorbed
mouth ~
across lining of
Injection

Intravenous (iv)
 directly
into vein
 rapid onset of effects


Fastest ~ Intramuscular (im)
Location important
 Deltoid
- rapid
 Thigh - moderate
 Buttocks - slowest
 Difference in blood
supply & distance
Routes of Drug Administration and Absorption.

Injecting
(Intravenous):
 Puts
drugs directly
into a vein
 Put drugs into
muscles or under
skin
Intravenous (IV)
Intramuscular (IM)
Subcutaneous
15 – 30 seconds
3 – 5 minutes
3 – 5 minutes
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Inc.
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Injection

Subcutaneous (sc)
 under
skin
 slow, steady absorption

Disadvantages
 Variable
absorption
 limited volume
 skin irritations ~
Injection

Intrathecal
 under
sheath of nerve fibers,
cord, or brain

spinal
Mostly as local anesthesia
 little
~
importance for most psychoactive drugs
Inhalation
Smoking
 Lungs

 gases
or vapors
 densely lined with capillaries
 large surface area

Fast absorption
 Similar
to iv ~
Routes of Drug Administration and Absorption.

Inhaling:
 Allows
the vaporized
drug to enter the
lungs, the heart and
then the brain in about
7-10 seconds (Most
rapid)


Inhaling: 7 to 10 seconds
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(Pictures)
Marijuana inhaling tent used
by the Scythians, c. 500 B.C.
Man in India smokes ganja
(marijuana) in a “chillum”
pipe.
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Inc.
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Other routes

Transdermal patches
 absorbed
by skin
 slow continuous release


also liposomes: via injection
Suppositories - rectal or vaginal
 absorption
incomplete & unpredictable
Pellets - Norplant
 Microcatheter & pump ~

Routes of Drug Administration and
Absorption
Contact or Transdermal
Absorption
Absorption through the
skin is the slowest
method of drug use. It
often takes 1–2 days
for effects to begin and
the absorption can
continue for about 7
days. Nicotine,
fentanyl, and heart
medications can also
be absorbed this way
Skin creams & ointments
absorbed through skin
Contact or
Transdermal:
1 to 2 days
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Inc.
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Toxicity
Toxicity is the ability of a chemical to
damage an organ system, to disrupt a
biochemical process, or to disturb an
enzyme system.
Drug Formulation
Dosage = the amount of drug to be administered
usually based on weight
Example: mg/kg
Concentration = how the drug is formulated
Example: mg/ml
Injection Volume = a liquid measurement
based on weight
Example: ml/kg
Factors Affecting Response to Drugs
Dosage
Route of Administration
IV IH
subling IM, SC
IP
PO
topical
Rate of Absorption
Rate of Elimination
Physiochemical properties of the drug
age, sex, species, metabolism, etc…
Drug-Receptor Interactions




Agonists
activates or enhances
cellular activity.
triggers a series of
biochemical events
alteration in function
second messengers:
biochemicals that
initiate these changes



Antagonists
do not initiate a change
in cellular function.
prevent the binding and
the action of agonists
“blockers”
Drug-Receptor Interactions
Factors Governing Drug Action

1. Affinity: measure of the tightness
that a drug binds to the receptor

2. Intrinsic activity: measure of the
ability of a drug to generate an effect,
producing a change in cellular activity
Binding of a drug

drug must interact with complementary
surfaces on the receptor.
Antagonist



exhibit affinity for the receptor
do not have intrinsic activity at the receptor
competitive antagonist: binds to the receptor
in a reversible mass-action manner
-agonists given in high concentrations  can
displace the antagonist from the receptor
-agonist can then produce its effect