Transcript File - Ms. Ward`s class!

Introduction to Pharmacology
1
What is Pharmacology?
• The science of pharmacology
involves the action of drugs on
humans and animals.
• The aim of drug therapy is to
diagnose, treat, cure, or lessen
the symptoms of disease.
• The study of pharmacology
applies properties and knowledge
of drugs, mechanism of drug
action, anatomy and physiology,
and pathology,
2
Drug Nomenclature
• All drugs are identified by a
generic name, a chemical
name, and a proprietary
(brand) name.
• The official name of the drug
is the generic name.
• The chemical name
describes the molecular
structure of the drug.
• The proprietary (brand)
name is assigned by the drug
manufacturer.
Prozac
Fluoxetine HCl
N-Methyl-3-phenyl-propylamine
3
Examples of Generic, Chemical, and Brand
Names
Generic Name
Chemical Name
Brand Name
Fluoxetine HCl
N-methyl-3-phenylpropylamine
Prozac
Acetaminophen
4-Hydroxyacetanilide
Tylenol
Ibuprofen
2-p-Isobutylphenylpropionic acid
Motrin
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Comparison Between Brand Name Drugs and
Generic Drugs
• The inventor of a new drug may apply for patent
protection. If awarded, the manufacturer is given up to
20 years exclusive rights to manufacture and distribute
the new drug.
• Once the drug is off the patent, other drug companies
may manufacture a generic equivalent.
• Generic drugs contain the same active ingredients as the
original manufacturer’s drug, in the same strength.
However, generic drugs may contain different inactive
ingredients, which may affect how much of the drug is
available to the body.
5
Comprehensive Drug Abuse Prevention
and Control Act (1970)
• Also known as the Controlled
Substance Act.
• The Act regulates drugs that
have a history for abuse.
• Controlled Substances are
placed in a “schedule” or
category according to their
abuse potential and effects if
abused.
• The “schedules” are
determined by Federal and
State laws.
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Controlled Substance Schedule
Schedule
Classification
Examples
C-I
These drugs have a high
potential for abuse. No medical
uses for treatment
Ecstasy, heroin, LSD,
marijuana, PCP
C-II
High potential for abuse. Has
accepted medical use for
treatment
Morphine, oxycodone,
methamphetamine
C-III
Less abuse potential than C-II
drugs. Accepted medical use.
Anabolic Steroids,
Hydrocodone
C-IV
Less abuse potential than C-III
drugs. Accepted medical use.
Valium, Xanex, Darvon,
Phentermine
C-V
Less abuse potential than C-IV
drugs. Accepted medical use.
Cough medicines with
Codeine
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FDA Pregnancy Safety Classification
• Class A – known to be safe
(Vitamins)
• Class B – probably safe (Penicillin,
Erythromycin)
• Class C – use cautiously if benefits
outweigh risks (heparin, antidepressants)
• Class D – known to cause fetal
problems. Use only if untreated
maternal disease is harmful to fetus
(Lithium, Phenobarbitol, Amiodorone)
• Class E – contradicted in pregnancy
(Coumadin, Methotrexate)
Thalidomide Baby
8
Drug Dosage Forms and Delivery Systems
• Drugs are created for delivery
by mouth (oral), injection
(parenteral), inhalation, or
topical application to the skin
or mucous membranes.
• Oral administration is safe,
easy, and generally more
economical than parenteral
administration.
• Common oral formulations
include: tablets, capsules,
solutions, emulsions,
syrups, suspensions, and
elixirs.
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Tablets
• Tablets are solid forms containing one or more active
ingredients plus binders, which allow the drug to take a
shape.
•
•
•
•
•
Delayed action tablets – slow the release of the drug to avoid destruction
of the drug in the stomach.
Enteric coated tablets – have an acid-resistant coating to prevent
dissolving in the stomach. Release contents into small intestine.
Sustained release (timed release) – deliver their contents over time (ex:
24 hours). Crushing may cause contents to be released immediately.
Chewable tablets – for people who have difficulty swallowing pills. Used
frequently with children.
Sublingual tablets – dissolved in the mouth, where many blood vessels
are located. Gets into bloodstream fast and by-passes stomach.
10
Capsules
• Capsules are solid
dosage forms containing
one or more active
ingredients plus binders
and fillers.
• Formulated to deliver their
ingredients immediately or
over time.
11
Oral Liquids
• Oral Liquids are easy to swallow
and work more rapidly than tablets or
capsules.
•
•
•
•
•
•
Suspensions – contain small drug
particles suspended in a liquid.
Solutions – drug particles are
completely dissolved in the liquid.
Syrups – contain a high concentration of
sucrose or other sugars.
Elixirs – contain between 5% and 40%
alcohol.
Tinctures – contain between 17% and
80% alcohol.
Emulsions – similar to suspensions.
May be dispersed in oil or water.
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Topical Administration
Ointments – semisolid preparations containing petroleum
or another base. Form a protective barrier between the
skin and harmful substances.
Creams – semisolid emulsions applied directly onto the
skin.
Suppositories – solid or semisolid dosage forms intended
to be inserted into a body orifice. Melt at body
temperature, dispersing the medicine
13
Transdermal Drug Delivery System
Transdermal patches are
controlled-released devices
that deliver medication across
skin membranes into the
general circulation. They
produce both local and
systemic effects.
Examples:
Nitroglycerin for angina
Estrogen for menopause
Fentanyl for pain
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Routes of Administration of Drugs
By Mouth, Oral (PO): The
major benefit of oral
administration is the
convenience to the patient.
-Oral medications are
systemic (work throughout
the body)
-Safer, because they take
time to work and therefore an
antidote can be given if
overdosed.
-However, these drugs do
not work as quickly
15
Routes of Administration of Drugs
Sublingual and Buccal Agents
(SL, Buccal): Few medications
are administered in this form, but
the medications administered in
this manner are very effective.
These medicines by-pass the
digestive system, and are
absorbed directly into the
blooodstream.
-Nitroglycerin is given
sublingually for Angina.
-Parcopa is given sublingually for
Parkinson’s
16
Routes of Administration of Drugs
Rectal Agent (PR): may be
used in patients who are
vomiting and cannot take
oral medications.
Suppositories or rectal
creams may be used.
These agents usually work
locally, not systemically.
-Suppositories for motion
sickness, nausea (systemic
effects)
-Laxatives (work locally)
17
Routes of Administration of Drugs
Topical Agents: topical agents can
have systemic or local effects.
They are popular due to the ease
of application, and the rapid effect
produced.
-Examples include Bacitracin
(antibiotics), Benadryl
(antihistamine), Estrogen patches
(hormonal), some blood pressure
medications, and smoking
cessation agents.
-May cause skin reactions.
-More expensive than oral
medications.
18
Routes of Administration of Drugs
Parenteral (Intravenous,
Intramuscular, Subcutaneous):
given “outside the intestines”.
-Benefits: speed of action, not
inactivated by stomach acids, not
harmful to the stomach.
-Disadvantages: increased risk
of infection, difficult to reverse
toxic or allergic effects, more
expensive, must be given by
trained medical personnel.
-Examples: Insulin, Heparin
(blood thinner), IV antibiotics,
chemotherapy.
19
Routes of Administration of Drugs
Inhalants: primarily used in
patients with respiratory (lung)
diseases. Also used to
anesthetize patients prior to
surgical procedures.
-Benefits: ease of use, quick
onset of action
-Disadvantages: must be used
properly to be effective.
-Examples: Albuterol Inhaler
(Bronchodilator for Asthma),
Nitrous Gas (anesthesia for
dental/surgical procedures).
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Pharmacokinetics
Once a drug is administered to a patient, the drug then undergoes
the 4 phases of Pharmacokinetics. These phases include:
-Drug absorption into the bloodstream
-Drug distribution to their site of action before they produce
their effects.
-Drug metabolism by the body
-Drug elimination from the body
These pharmacokinetic phases control the intensity of a drug’s
effect and the duration of the drug action.
21
Pharmacokinetics
The absorption of a drug is
dependent upon:
-the tissue thickness
-blood flow to the area
-drug concentration
-surface area (ex: microvilli
of the small intestines
-lipid solubility of the drug,
allowing it to pass through
the cell membrane
22
Pharmacokinetics
Drug distribution is the process of
movement of the drug from the
circulatory system, across barrier
membranes, to the site of drug action.
The quantity (volume) of drug distributed
is influenced by:
-the properties of the drug
-the extent of drug binding to blood
proteins
-the blood supply to the region
-the ability of the drug to cross natural
body barriers (ex: blood-brain barrier,
blood-placenta barrier)
23
Pharmacokinetics
Metabolism: most drugs are
transformed by enzymes
(usually in the liver) to a
metabolite that is less active
than the original drug.
Biotransformation is the process
of drug metabolism in the body
that transforms a drug to a
more active, equally active, or
inactive metabolite.
The main site of biotransformation
occurs in the liver.
24
Pharmacokinetics
Factors Influencing
Metabolism:
1. Liver Function: the liver
is the primary site for
metabolism. If the liver
function decreases,
metabolism decreases.
In cases of liver disease,
drug doses should often
be reduced because less
drug is capable of being
broken-down by the liver.
Jaundice –notice yellow sclera
25
Pharmacokinetics
Factors Influencing Metabolism:
2. Effects of Disease: Diseases like hepatitis decrease
the metabolic capacity of the liver. Lung disease and
Kidney disease can also reduce the body’s ability to
metabolize drugs.
3. Effects of Age: Metabolism in the liver is decreased in
both the elderly and in infants. Therefore, infants and
the elderly require lower doses of drug to produce
therapeutic effects.
26
Pharmacokinetics
Factors Influencing Metabolism:
4. Interactions of two or more drugs: Administration of
two or more drugs that both use the same metabolic
pathways can alter the metabolism of eachother.
-Ex: Phenytoin is a drug used to treat epilepsy.
Phenytoin can increase the metabolism of Warfarin, a
drug used to decrease blood clotting. This will make
Warfarin less effective.
-Ex: St. John’s Wart, an herb, can increase the
metabolism of birth control pills, causing a woman to
possibly get pregnant while “on the pill”.
27
Pharmacokinetics
Elimination is the final
pharmacokinetic phase.
Elimination results in the
removal of the drug from the
body, and discontinuation of
drug action.
The three major routes
of drug elimination are:
-kidney
-lung
-bowel
28
Pharmacokinetics
Elimination Half-life (T1/2) – the
time it takes for 50% of the drug to
be cleared (eliminated) from the
bloodstream.
It takes approximately 8 half-lives to
entirely eliminate a drug from the
body.
Every drug has its own unique halflife. It is important to know a
drug’s half-life, because it is an
indicator as to how long a drug will
produce effects in the body.
29
Pharmacokinetics
Bioavailability – the extent to which an administered
amount of drug reaches the site of action and is
available to produce drug effects.
Bioavailability is influenced by drug absorption and
distribution to the site of action.
Bioequivalent drugs – achieve the same maximum blood
concentration, in the same period of time.
30
Pharmacokinetics
The area under the curve (shaded area) is the measure of a drug’s
bioavailability
31
Two dose forms of the same
drug are depicted. These two
dose forms have equal
bioavailability and they are
bioequivalent.
Two dose forms of the same
drug are depicted. These two
dose forms have equal
bioavailability but they are
NOT bioequivalent.
32
Pharmacodynamics
Pharmacodynamics – is the
study of drugs and their
action on the living organism.
-looks at how the body
responds to drugs that are
administered.
Mechanism of Action –
describes how the drug
produces its effects.
33
Pharmacodynamics
Drug-receptor theory – drugs interact or bind with
targeted cells in the body to produce pharmacologic
action.
The location of the drug-cell binding is called the receptor
site.
34
Pharmacodynamics
Drug-receptor binding is similar to the action of a lock and
key. The drug is the key, and the receptor is the lock.
The more similar the drug is to the shape of the receptor
site, the greater the affinity (attraction) that the
receptor site has for the drug.
35
Pharmacodynamics
Types of Drug-Receptor
Interactions:
Drugs are described as agonists,
partial agonists, competitive
antagonists, and non-competitive
antagonists based on their effect
at the receptor site.
36
Pharmacodynamics
Agonist – is a drug that binds
to and activates the receptor
site, eliciting a response.
Partial Agonist – is a drug
that binds to a receptor, but
produces a reduced
(diminished) response,
compared with that of an
agonist.
37
Pharmacodynamics
Antagonist – binds to the receptor site and does not
produce an action. The drug prevents the binding of
agonists.
Competitive Antagonist – drug competes with the agonist
for the binding site of the receptor. If it binds, there is no
response.
Noncompetitive Antagonist – drug binds with an
alternative site on the same receptor (not at the same
site as the agonist), inactivating the receptor site.
38
Pharmacodynamics
Efficacy – describes the
maximum response
produced by a drug. It is a
measure of a drug’s
effectiveness.
-Agonists produce the
maximum drug response.
Which drug has higher efficacy,
Drug A or Drug B?
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Pharmacodynamics
Potency – Efficacy and
potency are related. Drugs
that have high efficacy at
low dose are very potent.
-Drugs that are very potent
require only a small dose to
produce a maximum drug
effect.
Which drug is more potent,
Drug A or Drug B?
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