Basics
An Introduction to
PHARMACOLOGY
• A drug is a chemical substance that alters a body
function,
• Drugs work at the cellular level,
• Drugs are distributed to ALL parts of the body via
blood, not just the to target organ, therefore,
• All drugs have side effects
Categorizing Drugs
Birth control
• Drugs can be categorized by
– 1. body system,
– 2. effect,
– 3. composition
Estrogen
Naming Drugs
• Chemical Name ( ie, proprionic acid)
• Proprietary, brand, trade name (Motrin)
– Protected for 17 years
• Generic Name (ibuprofen)
– Name given by U.S. Adopted Names Council
genitourinary
Questions
Controlling Drugs
• Below is the brand name and the generic name for
the same drug. Which is which and how do you
know?
Tequin ®
gatifloxacin
• FDA (Federal Drug Administration) measures
safety and effectiveness, determines if OTC
or prescribed, how to advertise
• DEA (drug enforcement agency) controls drugs
have abuse potential,
1
Scheduled Drugs
HEADING
superscription
BODY
Amoxicillin 500 mg.
Inscription
PRESCRIBING
DRUGS
Subscription
Disp: 4 tabs
Sig: Take all tabs 1 hr before dental appt.
Transcription
• Drugs are categorized 1,2,3,4 or 5, with 1
having most abuse potential, 5 least
• 1=no medical use
• 2 =written Rx needed, no refills
• 3 and 4=verbal Rx OK, 5 refills allowed
• 5=OTC in some states
CLOSING
Pharmocokinetics
Intraveneous
(Quickest route)
• Absorption – getting drug into
bloodstream
• Distribution – getting drug to
target organs and other sites
• Effect (stimulate or inhibit cells)
• Metabolism (biotransformation)changing drug for elimination
• Elimination – removal of drug
from body
Questions
Oral
(easy)
Intramuscular
(modifies irritating drugs)
-Absorption-Sublingual
(quick and easy)
Topical
(ControlledRoutes
effects)
(locally
effective)
of
Administration
Inhalation
-absorptionDrug must pass thru biologic membrane
to reach circulation
• Which of the previous routes are parenteral?
• Which of the previous routes bypass
absorption?
2
-absorptionDrug must pass thru biologic membrane
to reach circulation
Lipid soluble
water soluble
Mostly lipid
Mostly lipid
_
_
nonionized
_
_
Water pour
Water pour
ionized
Biologic Membrane
The pH of the water and whether the drug is
an acid or a base
What determines the amount of ionized vs nonionized drug?
Oral Administration
LIVER
• If drug is an acid,
– More drug is
nonionized when water
is acidic,(pH < 7.0)
– More drug is ionized
when water is basic
– Therefore acidic drugs
work better in an acidic
environment
• If drug is a base,
– More drug is
nonionized when water
is basic (pH > 7.0)
– More drug is ionized
when water is acidic
– Therefore more basic
drugs work better in a
basic environment
Nontarget organ
Target organ
First Pass Effect
• Oral medications pass
through liver first,
• Certain amount
metabolized and is
ineffective,
• Therefore some drugs
not given orally
(morphine)
-Distribution –
Protein Binding
Blood Vessel
LIVER
Drug A
Drug A
protein
Unbound drug effective
Why are some people more effected by a drug than others?
3
-Effect –
Potency
-Effect –
Efficacy
Drug A
Drug A
Target cell
Target cell
Drug B
Drug A
Drug B
Drug A
More potent
(Smaller doses needed)
-Effect –
Drug Interactions
Drug A more effective because
it attaches to more sites
Metabolism (biotransformation)
Drug A
nontarget
Drug A
Drug A
Target cell
Drug B
Target cell
Target cell
Drug A
• Most drugs metabolized in liver by
cytochrome P450 enzymes
• Some drugs metabolized by enzymes in
plasma
• Oral administered experience first pass
effect
• Rate of metabolism measured in half lives
Drug A
A drug’s Half Life
• The time it takes for half of the drug in the
circulation system to be metabilized
• Half life varies, long acting drug has a
longer half life
• After 5 half lives, drug is considered
ineffective
• 100% -50% - 25% - 12.5% - 6.25% - 3%
Excretion
• Most drugs excreted by kidneys, but also in
feces, saliva, sweat
• Kidney disease can lead to toxic amounts of
drug retained
4
Toxic Reaction
Adverse Reactions
• Side effects
– Predictable
• Toxic reaction ( target organ overreaction)
• Idiocyncratic reaction (genetic related
abnormal reaction)
• Allergic reaction
• If liver busy
metabolizing drug A
and drug B
metabolized by same
process, toxic levels
of drug B may
develop
LIVER
B A
Allergic Response
Allergic Response
Type I – anaphylaxis
(histamine release)
Type II – Cytotoxic
(Rh factor)
Common side effects with oral
implications
•
•
•
•
•
•
Xerostomia
Gingival hyperplasia
Bleeding
Nausea, vomiting,
Mucositis
Dysgeusia
Type III – immune complex
(Serum sickness)
Type VI – (cell mediated)
(contact dermatitis)
Therapeutic Index
• Measures the safety of a drug
• Numerator is the dose that kills 50% of test
animals - LD50 (lethal dose for 50%)
• Denominator is dose that produces desired
effect in 50% of test animals - ED50 (effective
dose in 50%)
• Drugs with index less than 10 are dangerous
• Ex. - LD50 of 100 mg / ED50 of 5 mg =TI of 20
5
-SummaryDrug Effectiveness
• Patient size - Redistribution and binding to non
target tissue decreases effect
• Liver function – Oral drugs pass thru liver before
target organ (first pass effect),
• Nutrition – Drug binds to protein in blood
• Acidity – If tissue acidic, drug will be ionized,
won’t pass cell membrane easily
6