Introduction to Pharmacology

Nurses plays an Integral role in administering

medication to patients, and depending on the
environment in which they work, could be
doing so as often as needed. As a result, it’s
imperative that nurses have a solid
understanding of pharmacology, and
potentially fatal drug interactions.
The nurse’s understanding of pharmacology is
important in her role of educating patients
about medications, dosages, and possible
side effects. A nurse who is not knowledgeable
about pharmacology can put patients at risk.

Terminologies
 Pharmakon - greek work for drugs.
 Logos - means study.
 Pharmacology - is a science that deals with
the study of drugs and their actions on living
organisms.
 Therapeutic Methods
- are the approaches to drug therapy.

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Drug Therapy
1. Treatment with drugs
2. Treatment by diet (ex. Low salt)
3. Physiotherapy (Treatment with natural or
physical forces such as light, water and heat)
4. Psychological therapy (identification of
stressors and methods to reduce stress and/or
use of drugs)

Drugs
- droog (dutch) means dry
- are chemical substances that have an effect on
living organisms
- Therapeutic drugs are often called medicines,
are those drugs used in the prevention or
treatment of diseases

Subdivisions of Pharmacology
 Pharmacognosy - concerned with the
botanical sources of drugs.
 Pharmacy - body of techniques involved in
the preparation, compounding, and dispensing
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 of drugs for medical use. Also, preservation
and storage of drugs.
 Pharmacodynamics - is the study of action
of drugs living tissues. It is concerned with
the response of the tissues to the chemical
agent used with the absorption to excretion
and fate of the chemical agent in the body.
 Pharmacotherapeutics - is the study of uses
of drugs in the treatment of the sick.
 Toxicology – is the study of the poisonous
effects that may be produced by drugs. It
deals with the symptoms of poisoning, with
the treatment and identification of poison

10 Rights of Drug Administration

1. Right Dose
2. Right Route
3. Right Time
4. Right Patient
5. Right Drug/Medication
6. Right Evaluation
7. Right Education
8. Right Assessment
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 9. Right Refuse
10. Right Documentation

Classification
- each drug can be categorized under a broad
subcategory/ies
- Example: Aspirin can relieve pain
(analgesic) and reduce fever (antipyretic)
- Other Classification: Adrenergic, Diuretics,
Emetics, Hypnotics and etc.
- the general information associated with each
drugs therapeutic uses, most common side
effects, precautions, contraindications,
interaction, drug names, dosage, and nursing
management.

Identifying Names
 Generic Name - common or general name
assigned to the drug differentiated from trade
name by initial lowercase letter never
capitalized.
 Prototype Drugs

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 -individual drugs that represent groups of
drugs
-may be the first drugs of this group to be
developed (e.g., penicillin for antibiotics,
morphine for opioid analgesics)
 Trade Name - the name which the
pharmaceutical company identifies its
product; copyrighted and used exclusively by
that company; can be distinguished from
generic name by Capitalized fist letter and
often shown on labels and references with the
symbol after the name (for registered
trademark)
 Chemical Name - the exact molecular
formula of the drug; usually a long, very
difficult name to pronounce and of little
concern to the health care worker.
 Official Name - name of the drug as it
appears in the official reference, the USP/NF;
generally, the same as the generic name.

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Legally Accessibility of the Drug
a. Over the counter (OTC) - no purchasing
restrictions
b. Legally Drugs - prescription drug;
determined unsafe for OTC purchase because
of possible side effects it takes
indiscriminately; includes birth control pills,
antibiotics, cardiac drugs, hormones etc.
indicated in the Physician’s desk reference by
the symbol to the far right of the trade name.
c. Controlled Substance - drug controlled by
prescription requirement because of the danger
of addiction or abuse; indicated by schedule
of numbers C-I to C-V

Categories of Controlled Substances

 Schedule I: Drugs with no current medical
use with high potential for abuse and/or
addiction.
Ex: LSD, heroin, peyote, marijuana, ecstasy
(3,4 methyenedioxy - methamphetamine)
 Schedule II: Drugs with some medically
acceptable uses, but with high potential for
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 abuse and/or addiction. These drugs can be
obtained through prescription.
Ex. (methadone, meperidine, cocaine,
pentobarbital, tylox)
 Schedule III: Drugs with low to moderate
potential for abuse and/or addiction, but
less dangerous than Schedule I or II. These
drugs can be obtained through prescription,
but generally are not available over the
counter.
Ex. (Vicodin, Tylenol with codeine)
 Schedule IV: Drugs with viable medical use
and low probability of use or misuse.
Ex. (Valium, Dalmane, Klonopin)
 Schedule V: Drugs with low potential for
abuse (lower than Schedule IV).
Ex. (atropine and dipheoxylate)

Pregnancy Categories
Category A - studies in pregnant women failed
to show risk to the fetus.

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Category B - animal studies have failed to
show a risk to the fetus and there are no
adequate studies in women.
Category C - animal studies have shown an
adverse effect on the fetus, no adequate human
studies, benefits may outweigh risks.
Category D - positive evidence of human fetal
risk.
Category X animal or human studies have
shown fetal abnormalities or toxicity.

Drug Addiction
Indications - a list of medical conditions or
diseases for which the drug is meant to be used.
Actions - a description of the cellular changes
that occur as a result of the drug.
Contraindication - a list of conditions for
which the drug should not be given.
Cautions - a list of conditions or types of
patients that warrant closer observation for the
specific side effects when given drug.

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Side effects and adverse reaction – a list of
possible unpleasant or dangerous secondary
effect, other than desired effect. EX. Benadryl
(SE: dizziness, sedation, epigastric distress,
disturbed coordination, anorexia and thickening
bronchial secretions)

3 Side Effects Associated with Antibiotics

 Ototoxicity – causes damage to the 8th
Cranial nerve. Damage maybe
reversible or permanent.
 Nephrotoxicity - damage to the
kidneys, resulting to impaired kidney
function, decreased output and renal
failure.
 Photosensitivity - increased reaction to
sunlight with the danger of intense
sunburn
Interactions - A lists of drugs or foods that
may alter the effect of the drug and usually
should not be given during the same course
of therapy. Ex. MAO inhibitors intensify
effect of Benadryl causing serious BP
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 changes and death when taken with other
drugs and some food.

Sources of Drugs
 Plants
 Minerals
 Animals
 Synthetic

Effects of Drugs
 Systemic - reaches widespread area of
the body
 Local - is limited to area of the body
where it administered
PHARMACOKINETICS - the study of how
the body interacts with administered substances
for the entire duration of exposure
LADME- describes the pharmacokinetic
processes which follow a given dosage
regimen.
 L = Liberation, the release of the drug
from its dosage form. It is the first step in

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 the process by which medication enters
the body and liberates the active
ingredient that has been administered.
 A = Absorption, the movement of drug
from the site of administration to the
blood circulation.
- Factors affecting absorption include:
dosage form, route of administration,
blood flow to the site of
administration, gastrointestinal
function, presence of food or other
drugs
- For many medications, food in the
stomach slows absorption

 BIOAVAILABILITY- Is the portion of

a dose that reaches the systemic
circulation and is available to act on
body cells. EX. IV administration
(100%), Subcutaneous, Oral route.
- Mucous membranes allow for rapid and
direct absorption into the bloodstream

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 HALF LIFE- refers to the
measurement of the time it takes the
body to break down and excrete one
half of the drug.
- varies from person to person, based on a
person’s weight, gender, health, and
many other factors

 D = Distribution, the process by which

drug diffuses or is transferred from
intravascular space to extravascular space
(body tissues).
- Protein binding is an important factor
in drug distribution
- allows a part of a drug dose to be stored
and released as needed (plasma
proteins(albumin): carrier)
- Drug distribution into the CNS is
limited because of the blood-brain
barrier
 Blood-brain barrier - is composed of
capillaries with tight walls which limits

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 movement of drug molecules into brain
tissue. (Drugs that are lipid soluble)
 Drug distribution during pregnancy and
lactation is unique as most drugs cross
the placenta or in the case of lactation,
pass into breast milk

 M = Metabolism, the chemical

conversion or transformation of drugs
into compounds which are easier to
eliminate.
- Most drugs are metabolized by the
cytochrome P450 enzymes in the liver
- Liver contains complex system of
enzymes, three of which are key in the
metabolism of medications/drugs
 Cytochrome p450 - enzymes catalyze
the chemical reactions which ultimately
metabolize the medications
 Enzyme
 First Pass Effect – (also known
as first-pass metabolism or pre-
systemic metabolism) is a phenomenon
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 of drug metabolism whereby the
concentration of a drug, specifically
when administered orally, is greatly
reduced before it reaches the systemic
circulation.
 Serum Drug Levels- Lab measurement
of the amount of a drug in the blood at a
particular time

 Minimum effective concentration

(MEC)- must be present before a drug
exerts its pharmacologic action on body
cells
 Duration of action-time- during which
serum drug levels are at or above the
MEC (may measure serum drug levels
when the drugs have a low therapeutic
index)

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 E = Excretion, the elimination of
unchanged drug or metabolite from the
body via renal, biliary, or pulmonary
processes
 Hepatic drug metabolism- or
clearance is a major mechanism for
terminating drug action and
eliminating drug molecules from the
body

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PHARMACODYNAMICS – the response of
the body to the drug. (receptors)

Drug-receptor complex initiates

physiochemical reactions that stimulate or
inhibit cellular functions
 Receptors vary in type, location,
number and functional capacity
 Agonists - is a drug that combines
with a receptor to bring about an
action. Examples of Opioid
agonists: Morphine, Hydrocodone
(pain relief /euphoria)

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  Antagonists- combines with a
receptor and blocks the action.
Examples include: antacids,
osmotic diuretics,
chelators(Naloxone (Narcan),
Naltrexone and Nalmefene)
 Antidote - is a drug, chelating substance,
or a chemical that counteracts (neutralizes)
the effects of another drug or a poison.

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DRUG INTERACTIONS
 Synergism - the action of 2 drugs working
together in which one helps the other
simultaneously for an effect that neither
could produce alone. Drugs that work
together are synergistic. EX. Morphine and
oxycodone
 Desirable synergism- giving small amounts
can relieve pain safely ex. Promethazine
(phenergan) and meperidine (demerol).
Large amounts could be addictive.
 Undesirable synergism- sedatives and
barbiturates given in combination can
depress CNS to dangerous levels depending
on the strength of each
 Potentiation- the action of 2 drugs in which
one prolongs or multiplies the effect of the
other.
 Desirable potentiation- when one drug
does not elicit a response on its own but
enhances the response to another drug.

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 Undesirable potentiation- toxic effect may
result

Variables that Affect Drug Actions

 Dosage
 Route
 Drug-diet interactions
 Antidote
 Age
 Pregnancy
 Body weight
 Gender-hormonal effects
 Pathologic condition
 Placebo response
DOSAGE- amount of drug given for a
particular therapeutic or desired effect.
1. Minimum dose- smallest amount of
drug that produce therapeutic effect

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2. Maximum dose – largest amount of
drugs that will produce desired effect
without producing symptoms of toxicity
3. Loading dose – initial high dose (Max.
dose) uses to quickly elevate the level
of drug in the blood followed by a series
of low maintenance doses.
4. Maintenance dose- dose required to
keep the blood level at a steady state in
order to maintain the desired effect
5. Toxic dose- amount that will produce
harmful side effects or symptoms of
poisoning
6. Lethal dose- dose that causes death
7. Therapeutic dose- customarily given
(ave. adult dose based on body weight
of 150lbs; adjusted according to
variations from the norm

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ROUTE
2 Category
1. GI routes
 Oral (PO)
 Nasogastric (NG)
 Rectal (R)
2. Parenteral
 Sublingual( SL) or buccal
 Injection routes
 Intravenous (IV)
 Intramuscular (IM)
 Subcutaneous (subQ)
 Intradermal (ID)
 Intracardiac, intraspinal,
intracapular
 Topical (T)
 Dermal (D)
 Mucosal
 Inhalation

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Oral route –easiest
IV route – fastest administered by IV push or
bolus (Concentrated drug solution)or diluted
infused slowly by IVdrip
-administered by physician, RN or paramedic
-best route for emergency treatment
Parenteral routes- are choice if NPO status or
drug not suitable for GI absorption
IM route – is fairly rapid because muscles are
highly vascular, desirable to retard the speed of
absorption, can be added to oily base drugs
UNEXPECTED RESPONSES TO DRUGS
TERATOGENIC – causes development of
physical defects to fetus in vitro
IDIOSYNCRACY – unique, unusual response
to a drug. Ex. Tranquilizer causes agitation and
excitement rather than tranquility
PARAXODICAL- Opposite effect from that
expected

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TOLERANCE – decreased response to a drug
that develops after repeated doses. To achieve
desired effect dosage is increased or replaced.
DEPENDENCE- Acquired need for a drug
that may produce psychological or physical
symptoms of withdrawal when drug is
discontinued.
Psychological-craving, no physical symptoms
of withdrawal other than anxiety
Physical – cells actually have need of the drug
like retching, nausea, pain tremors or sweating
HYPERSENSITIVITY –immune response
(allergy) to a drug in varying degrees
-rash, hives after 3-4 days of drug therapy

ANAPHYLACTIC REACTION – severe,

possibly fatal. Allergic (hypersensitivity)
response. Signs are itching, urticarial(hives),
hyperemia (reddened warm skin) vascular

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collapse, shock, cyanosis, laryngeal edema,
dyspnea.

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