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Introduction to Pharmacology for Nursing Students
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The word Pharmacology is derived from Greek – pharmacon means drug and logos mean study
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PHARMACOKINETICS: Pharmacokinetics is the study of the absorption distribution, metabolism, and
excretion of drugs,i
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INTRODUCTION TO PHARMACOLOGY DEFINITION: PHARMACODYNAMICS: Pharmacodynamics is the
study of the effect of the drugs on the body and their mechanism of action,i
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THERAPEUTICS: Therapeutics deals with the use of drugs in the prevention and treatment of
disease
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e detection, prevention, and treatment of poisoning
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the term now also includes the
use of chemicals to create malignancies
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It also includes collection, isolation, purification, synthesis, and
Standardization of medical substances
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SOURCES OF DRUGS

The sources of drugs could be natural or synthetic, NATURAL SOURCES: 1
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g Atropine,
Morphine, Quinine,digoxin,pilocarpine, physostigmine
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ANIMALS e
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Insulin, heparin,
gonadotrophins, and antitoxic sera
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MINERALS, Magnesium sulfate, Aluminium hydroxide, iron,
sulfur, and radioactive isotopes
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MICROORGANISMS, Antibacterial agents are obtained from some
bacteria and fungi
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g Immunoglobulin from blood, growth hormone from
the anterior pituitary, and chorionic gonadotrophins from the urine of pregnant women
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e
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Many drugs are obtained from cell culture,e
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some are now
produced by recombinant DNA technology,e
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g monoclonal antibodies
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Knowledge of the advantages and
disadvantages of the routes of drug administration is essential
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ENTERAL ROUTE (ORAL INGESTION )
This is the most common, oldest, and safest route of drug administration
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ADVANTAGES: 1
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Most convenient 3
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Drugs can be self-administered 5
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Onset of action is slower as absorption needs time
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Irritant and unpalatable drugs cannot be administered
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Some drugs may not be absorbed due to certain physical characteristics, e
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e
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8
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ENTERIC COATED TABLET
Some tablets are coated with substances like cellulose- acetate, phthalate, gluten, etc
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This will 1
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2
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3
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4
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Therapeutic concentration may be
maintained for a long time especially when nocturnal symptoms are to be treated
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There may be releases of the entire amount of the drug in a short time
leading to toxicity
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PARENTERAL ROUTE
Routes of administration other than the enteral route are known as parenteral routes
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ADVANTAGES: Action is more rapid and predictable than oral administration
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Gastric irritants can be given
parenterally and therefore irritation to the GIT can be avoided
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In emergencies, parenteral routes
are very useful
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DISADVANTAGES: Asepsis must be maintained
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More expensive less
safe and inconvenient
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The parenteral route includes:
1
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Inhalation
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Transmucosal route
INJECTION Intradermal The drug is injected into the layers of the skin by
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g
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g
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Only a small quantity can be administered by this route and it may be painful
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g
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As this
tissue is less vascular, absorption is slow and largely uniform and this makes the drug long-acting
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In shock
absorption is not dependable because of vasoconstriction
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Drugs can also be administered subcutaneously as
1
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The solution gets deposited in the SC tissue from where it is absorbed
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It is suitable for vaccines
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pellet implantation: Small pellets packed with drugs are implanted SC
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g, testosterone,
desoxycorticosterone acetate
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sialistic implants: The drug is packed in sialistic tubes and implanted SC
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g
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The
empty nonbiodegradable implant has to be removed
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Absorption into the plasma occurs by simple diffusion
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As the muscle is vascular, absorption is rapid and quite uniform
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The
volume of injection should not exceed 10ml
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oily solution or suspension, the
absorption is slow and steady
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Soluble substances, Mild irritants, depot preparations,
suspensions, and colloids can be injected by this route
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ADVANTAGES: Intramuscular route is reliable
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DISADVANTAGES: IM injection may be painful
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Risk of nerve injury
–irritant solutions can damage the nerve if injected near the nerve
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INTRAVENOUS (IV) Here, the drug is injected into one of the superficial veins so that it directly
reaches the circulation and is immediately available for action
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A bolus: the drug is dissolved in a suitable amount of vehicle and injected slowly
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g
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2
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g
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3
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g
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g
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It gives 100% bioavailability
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Rapid dose adjustments are possible-if unwanted effects occur, the
infusion can be stopped
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Irritation of the vein may
cause thrombophlebitis
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The solution should be sterile and strict
aseptic measures should be taken
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Before starting infusion the IV line
should be flushed with saline
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Make sure that there are no air bubbles in the syringe and tubing
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This route is also used for peritoneal dialysis
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g

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some antibiotics and corticosteroids are also injected by this route to
produce high local concentrations
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strict aseptic precautions are
required,e
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hydrocortisone is injected into the affected joint, in rheumatoid arthritis
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it is used only in the
treatment of peripheral vascular disease, local malignancies, and angiograms
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Inhalation: Volatile liquids and gases are given by inhalation,e
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Solution of drug particles
and the fine droplets are inhaled as aerosol, e
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Salbutamol
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ADVANTAGES: Almost instantaneous absorption of the drug is achieved because of the large
surface area of the lungs
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Absorption and excretion
through lunges
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TRANSDERMAL ROUTE: Highly lipid-soluble drugs can be applied over the skin for prolonged
absorption,e
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Adhesive units, inunction,
iontophoresis, and jet injection are some forms of transdermal drug delivery
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site of
the application is the chest, abdomen, upper arm, back, or mastoid region,e
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ADVANTAGES: Duration of action is prolonged
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Patient
compliance is good
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Iontophoresis: In this procedure, galvanic
current is used for bringing about the penetration of lipid insoluble drugs into the deeper
tissues where its action is required,e
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salicylates, fluoride iontophoresis is used in the
treatment of dental hypersensitivity
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It includes sublingual, nasal, and rectal
routes
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it dissolved and the drug is absorbed across the sublingual mucosa,e
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Nitroglycerin,
nifedipine, buprenorphine
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ADVANTAGES: Absorption is rapid –within minutes the drug reaches the circulation
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After the desired effect is obtained, the drug can be spat out to
avoid unwanted effects
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Nasal: Drugs can be administered through the
nasal route
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g
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Rectal:
Rectum has a rich blood supply and drugs can cross the rectal mucosa to be absorbed for
systemic effect
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e
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ADVANTAGES: Gastric irritation is avoided
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Useful
in geriatric patients and others with vomiting and those unable to swallow
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Absorption may be irregular and unpredictable
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enema may be an
evacuant or retention enema
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it is given before surgeries, obstetric procedures, and
radiological examination of the gut
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e
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TOPICAL: Drugs may be applied on the skin for local action as an ointment, cream, gel,
powder, paste, etc, drugs may also be applied on the mucous membrane as in the eyes, ears,
and nose as ointment, drops, and sprays
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e
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SPECIAL DRUG DELIVERY SYSTEM: To improve drug delivery, prolong the duration of action and
improve patient compliance, special drug delivery systems are used
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Russert: Ocusert
systems are thin elliptical units that contain the drug reservoir which slowly releases the drug
by diffusion
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g pilocarpine ocusert used in glaucoma is placed under the lid can deliver
the pilocarpine for 7 days
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Transdermal adhesive units: A prodrug is an inactive form of a drug that gets metabolized to
the active derivative in the body
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g dopamine does not cross BBB but levodopa a prodrug
crosses BBB and it is converted to dopamine in the CNS
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Osmotic pumps are small tablet shape units containing the drug and osmotic substances in two
different chambers the tablet is swallowed and reaches the gut, water enters the tablet
through SPM
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Computerized miniature pumps: These are Programmed to release drugs at a definite rate and
continuously
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g insulin and anticancer drugs
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Liposomes are phospholipids suspended in aqueous vehicles to form minute vesicles

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mainly used for malignant tumors
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History of allergy should be taken particularly before parenteral administration
of the drugs
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Drugs should be kept in a safe place
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PHARMACOKINETICS
PHARMACOKINETICS Pharmacokinetics is the study of the absorption, distribution, metabolism,
and excretion of the drugs, i
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once the drug is administered it is absorbed,i
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enters the blood is distributed to different
parts of the body, reaches the site of action, is metabolized, and excreted
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Drugs may be transported across the membrane by passive or active transport
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Active transport It is the transfer of drugs against a concentration gradient and needs energy
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only drugs related to natural metabolites are
transported by this process, e
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ABSORPTION
Absorption is defined as the passage of the drug from the site of administration into circulation
for a drug to reach its site of action, it must pass through various membranes depending on the
route of administration
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e
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Thus except for the IV route, absorption is important for all other routes of
administration
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they are:
1
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then it has to dissolve in the GI fluids
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liquids are absorbed faster than
solids
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Drugs like
corticosteroids, griseofulvin, digoxin, aspirin, and tolbutamide are well absorbed when given as
small particles
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Lipid solubility: lipid-soluble drugs are absorbed faster and better by dissolving in the
phospholipids of the cell membrane
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pHand ionization: Ionized drugs are poorly absorbed while unionized drugs are lipid-soluble
and are well absorbed
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g aspirin, barbiturates
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g pethidine,
ephedrine
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g heparin,
streptomycin
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Area and vascularity of the absorbing surface: larger area of the absorbing surface and more
the vascularity – better is the absorption
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Intestinal motility – when
motility is highly ed as in diarrhea, drug absorption is reduced
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Presence of food: Drugs may form complexes with food, such complexes are poorly
absorbed
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g
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g
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10
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First, pass metabolism First-pass metabolism is the metabolism of the drug during its passage
from the site of absorption to the systemic circulation
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Drugs given orally may be metabolized in the gut wall and the liver
before reaching the systemic circulation
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FPM may result in partial to total inactivation of the drug
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g nitroglycerin,
salbutamol
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IV -100% Bioavailability ,chlortetracycline 30%,chloroquine 80%
,diazepam 100%
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Distribution After a drug reaches the systemic circulation, it gets distributed to various tissues
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like absorption
distribution also involves the same process,i
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Various factors determine the rate and extent of distribution, they are lipid solubility,
ionization, blood flow, and binding to plasma proteins and cellular protein
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The free or
unbound fraction of the drug is the only form available for action, metabolism, and excretion,
The protein-bound form serves as a reservoir
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e
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One drug may displace
another binding site and result in displacement interaction, warfarin 99% PB indomethacin
reduces its binding to 95%
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Tissue binding: some drugs get bound to certain tissue constituents because of a special
affinity for them
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Lipid soluble
drugs like thiopentone sodium are bound to adipose
tissue,bone-tetracycline,retina-chloroquine, thyroid- iodine
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moreover, glial cells envelop
the capillaries and together these form the BBB
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E
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Penicillin readily penetrates BBB
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Metabolism or biotransformation is the process of biochemical alteration of the drug in the
body
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These processes convert the drugs into more polar,
water-soluble compounds so that they are easily excreted through the kidneys
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g frusemide, atenolol
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The chemical reactions of biotransformation can take place in two phases, 1
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if the metabolites are not water-soluble it undergoes phase II reactions
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phase II (Synthetic reaction): in this reaction water-soluble substances present in the body
like glucuronic acid, sulfuric acid, or an amino acid combine with the drug to form highly polar
compounds excreted by the kidneys
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Drugs are small amounts are excreted in saliva, sweat, and milk
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highly lipid-soluble drugs are reabsorbed in the renal
tubules, so their excretion is slow
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large water-soluble conjugates are excreted in the bile
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g
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The minimum dose is the smallest dose required to produce the
desired therapeutic effect of the drug
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A toxic dose is the dose of
the drug which produces undesirable effects in the majority of the patients Lethal dose is the
dose of the drug which can cause death
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g lethal dose of phenobarbitone is 6-10gm
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PHARMACODYNAMICS Pharmacodynamics is the study of the actions of the drugs on the body
and their mechanism of action, i
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Drugs produce
their effects by interacting with the physiological system of the organisms
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e
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Thus drugs act by
1
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Depression
3
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Replacement
5
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Modification of the immune status Stimulation is thees inactivity of the specialized cells,
e
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Depression is the es inactivity of the specialized cells, e
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Irritation: This can occur on all types of tissues in the body and may result in inflammation,
corrosion, and necrosis of cells
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g insulin in
diabetes, iron in anemia,vit C in scurvy
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g penicillin, cytotoxic effect on cancer cells
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g glucocorticoids
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Local: drugs may
act at the site of application
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g antibiotics,antifungal agent
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the fundamental mechanism of
drug action may be: Through receptor Through enzymes and pumps Through ion channel By
physical action By chemical interaction By altering metabolic processes

Through receptors, Drugs may interact with specific receptors in the body
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g
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Through ion, channel Drugs may interfere with the movement of ions across
specific channels, e
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Ca channel blocker, K channel blocker
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E
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absorption –activated charcoal in poisoning
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Antacids - Neutralize gastric acids Oxidising agents - kmno4 (germicidal) Alternating
metabolic processes drugs like antimicrobial alter the metabolic pathway in the microorganism
destroying MO
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g sulfonamides interfere with bacterial folic acid synthesis
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Receptors are proteins
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Functions of
receptors The receptor has to identify the compound, and when the compound binds to the
receptor, it has convey the message to bring about a response
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Antagonist: An antagonist is a
substance that binds to the receptor and prevents the action of an agonist on the receptor
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Drug synergism and antagonism When two or more drugs are given concurrently, the effect
may be additive, synergistic, or antagonistic
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e
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Ephedrine with
theophylline in bronchial asthma
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here the total effect of the
combination is greater than the sum of their independent effect
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e
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Antagonism: one drug opposing or inhibiting the action of another drug is antagonism
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g
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Physiological antagonism:
Two drugs act at different sites to produce an opposing effect
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g
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Antagonism at the receptor level The antagonist
inhibits the binding of the agonist to the receptor
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Reversible competitive antagonism: The agonist and antagonist compete for the same receptor
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it is thus
reversible antagonism
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the antagonism can be
overcome by increasing the concentration of Ach at the receptor
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it blocks the agonist the blockade cannot be overcome by increasing the dose of the agonist
hence it is irreversible antagonism,e
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Adrenaline and phenoxybenzamine at - adrenergic
receptor
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they are
1
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for obese
and underweight persons, the dose has to be calculated individually
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Age: In the newborn, the liver and kidney are not fully mature to handle the drugs,e
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Young's
formula, child's dose = age (years) x adult dose age +12
3
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special care is necessary while prescribing for pregnant and lactating women during
menstruation
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species and race: response to drugs may vary with species and race
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g
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5
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e
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tetracycline forms
complexes with Ca present in the food and are poorly absorbed
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6
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e
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Mgso4 given orally is a purgative, in IV it causes CNS depression and has
anticonvulsive effects
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7
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The response of the drugs
differs according to the metabolizing enzymes
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Acetylation of drugs: the rate of drug
acetylation differs among individuals people may be fast or slow acetylators
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g
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B
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incase some drugs further increase the drug response
is lowered
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g
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g
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10
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Cumulation: Drugs
like digoxin which are slowly eliminated may cumulate resulting in toxicity
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A
lethal dose of Morphine is 250 mg, an addict can tolerate morphine in gm
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when some drugs are administered
repeatedly at short intervals, tolerance develops rapidly and is known as tachyphylaxis or acute
tolerance
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Psychological factor: the doctor-patient relationship as well as the nursing care influence
the response to a large extent by acting on the patient's psychology
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placebo is the inert dosage form with no biological activity but only resembles the actual
preparation in appearance
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presence of other drugs: The concurrent use of two or more drugs can influence the
response of each other

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