Transcript Principles of Drugs

Principles of Drugs
Testing of the new drugs
before use
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Not teratogenic ( causes birth defect)
Carcinogenic ( causes cancer)
Toxicity studies not harmful to body system.
It should specific in action and its mechanism of
action understood as complitly as possible.
• Optimal route of administration.
Phases of new drug developments (FDA)
• Animal Trials
• Phase 1: the drug is tested on
healthy volunteers.
• Phase 2: involves trials with human
subjects who have the disease.
• Phase 3: large number of patients
receive drug to provide information
about adverse effect.
• Phase 4: post market surveillance.
Resources for Drug Information
• Pharmacopedia
– Official resource
– US Pharmacopedia, British Pharmacopedia
• Compendia
– Non Official
– American Formulary, Facts & Comparisons, USP Dispensing
• Journals
– Nursing 2005
– AJN
– RN
• Nursing Reference Books
• Web sites
Pharmacokinetics
• Absorption
• Distribution
• Metabolism
• Excretion
• Absorption: means the transfer of
the drug from the external to the
internal environment of the body.
Absorption
•Oral Preparations
Liquids, elixirs, syrups
Suspension solutions
Powders
Capsules
Tablets
Coated tablets
Enteric-coated tablets
Fastest
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Slowest
Absorption
Factors That Affect Absorption
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Administration route of the drug
Food or fluids administered with the drug
Dosage formulation
Status of the absorptive surface
Rate of blood flow to the small intestine
Acidity of the stomach
Status of GI motility
Distribution
• The transport of a drug in the body
by the bloodstream to its site of
action.
• Protein-binding
• Water soluble vs. fat soluble
• Blood-brain barrier
• Areas of rapid distribution: heart,
liver, kidneys, brain
• Areas of slow distribution: muscle,
skin, fat
First-Pass Effect
• The metabolism of a drug and its passage
from the liver into the circulation.
• A drug given via the oral route may be
extensively metabolized by the liver before
reaching the systemic circulation (high firstpass effect).
• The same drug—given IV—bypasses the
liver, preventing the first-pass effect from
taking place, and more drug reaches the
circulation.
Metabolism
(also known as Biotransformation)
• The biologic transformation of a drug into
an inactive metabolite, a more soluble
compound, or a more potent metabolite.
• Liver (main organ)
• Kidneys
• Lungs
• Plasma
• Intestinal mucosa
Factors that decrease metabolism:
• Cardiovascular dysfunction
• Renal insufficiency
• Starvation
• Obstructive jaundice
• Erythromycin or ketoconazole drug
therapy
Factors that increase metabolism:
• Barbiturates
• Rifampin therapy
Delayed drug metabolism results in:
• Accumulation of drugs
• Prolonged action of the effects of the
drugs
Excretion
• The elimination of drugs from the
body
• Kidneys (main organ)
• Liver
• Bowel
– Biliary excretion
– Enterohepatic circulation
Half-Life
• The time it takes for one half of the
original amount of a drug in the body
to be removed.
• A measure of the rate at which drugs
are removed from the body.
Pharmacodynamics
• Onset
The time it takes for the drug to elicit a
therapeutic response
• Peak
The time it takes for a drug to reach its
maximum therapeutic response
• Duration
The time a drug concentration is sufficient to
elicit a therapeutic response
Pharmacodynamics
Drug actions:
• The cellular processes involved in
the drug and cell interaction
Drug effect:
• The physiologic reaction of the
body to the drug
• The receptor: are protein that may occur
on the surface of the cell.
• They have two important functions:
• To bind the body own chemical messenger
such as hormones and neurotransmitters.
• To convert into signals that the cell can
recognize and respond to.
• Two important properties:
• Specificity
• Affinity
• Agonists: the ability of drug to bind
receptor (drug that produce response).
• Antagonist: drug that blocks the action
of antagonist. ( Naloxone).
• Partial agonist: is a drug that is able to
both stimulate and block at receptor
Principles of Drug and Dosage
Administration
• Drugs may have more than one indication, i.e. each
may have more than one action depending upon
dosage
– Aspirin given in low doses to relieve pain & high
doses to suppress inflammation (arthritis)
• Drugs can be administered by different routes and
dosage depends on route given.
• Oral doses usually larger than injected doses and
may be fatal if given by incorrect route
• Certain IV drugs can cause local injury if intravenous
line becomes extravasated.
Guidelines to help ensure correct
administration
• Read medication order carefully
• Verify identity of patient with drug order.
• Read medication label & verify
– Drug itself
– Amount of drug
– Verify suitability for administration by intended
route
• Verify dosage calculations
• Use special handling if drug requires
DO NOT ADMINISTER ANY DRUG IF YOU DO NOT
UNDERSTAND THE REASON FOR ITS USE
Therapeutic Objective
- To provide maximum benefit with
minimum harm.
**Must also be ready to respond to
interaction between drug and patient (i.e.,
must be aware of drug REACTIONS and
SIDE EFFECTS)**
Evaluating and Promoting Therapeutic
Effects
• Is the drug doing the right thing?
– Must know rationale for treatment and the nature
and time course of desired response
• If do not have this then cannot make judgment of
progress
• If desired response do not occur then must act
quickly.
• Give alternative therapy
– Even if patient gains beneficial responses, must be
aware of what drug is supposed to do, because it
still might end up badly
– Nifedipine: given for hypertension & angina
pectoris: when given to treat hypertension should
monitor for reduction in blood pressure; if used for
treatment of angina, need to monitor for reduction
in chest pain.
Minimize Adverse Effects
• Know patient history
– Understand disease and treatment and what
drug is supposed to do (again, do not give
drug blindly!!!)
– Identify high risk patient
– Educate patient
– Know adverse effects of drug and educate
patient.
• Know drug interactions with other medications
– This is important part of patient history
Promote Compliance
• Drugs must be taken correctly
– Wrong dose
– Wrong route
– Wrong time
• Educate patients to how to self medicate with
specific instructions
– If elderly must also give instructions to another
responsible party.
• Implement Non-drug measures to enhance drug
effects
– Breathing exercises, biofeedback, emotional
support, exercise, physical therapy, rest, weight
reduction, stop smoking, and sodium restriction
(must evaluate individual patient for specific
needs)
Patient Education
• Drug name and therapeutic category (penicillin &
antibiotic)- give generic name and trade name
• Dosage size
• Dosing schedule (PRN not fixed)-what to do if
missed?
• Route and technique of administration.
• Expected therapeutic response and when it
should develop
• Non drug measures to enhance therapeutic
responses
• Duration of treatment
• Method of drug storage
Pharmacology and the Nursing Process
Nursing Process
1) assessment
2) nursing diagnosis
3) planning- individual for each patient
4) implementation- some collaborative with
physician and others are independent
5) evaluation- degree to which drug therapy is
successful
Pre-administration Assessment
• Establishes the baseline data needed to tailor
drug therapy to the individual patient: maximizes
benefits and minimizes harmful effects
– Collection of baseline data needed to evaluate
therapeutic responses- beneficial: know the
symptoms so you know what baseline data to
collect
• blood chemistry profiles
• Blood pressure
• Organ enzyme levels (heart, liver, kidney,…)
• Collection of baseline data needed to evaluate
adverse effects:
– Even without baseline data, adverse affects
may be obvious (hair loss, pain, vomiting,
insomnia)
– Less obvious are organ functions (liver,
kidney,)
• Identification of high risk patients:
– Depends on symptoms and drug chosen (if
patient has kidney dysfunction and drug is
eliminated primarily through kidney, then drug
will accumulate and may be toxic)
– Impaired kidney & liver
Assessment of patient’s capacity for self-care– Must be willing and able to administer drugs in
correct dosage and at correct time
• Evaluate patient intelligence
• Patient physical capacity to self administer
• Mental illness (will they take drug?)
• Financial ability to pay for and get drug
• Religious beliefs concerning drugs and
medications
– Understanding of patient that drug is needed
in prescribed amount (even when they feel
better)
– Assess and discuss with physician
Nursing Diagnoses and Analysis of Drug:
• Judge appropriateness of prescribed regime
• Identify potential health problems that drug
might cause
• Determine patient’s capacity for self care
– Nurse can question appropriateness of drug!
• must know action of drug
• contraindications of drug
• Potential benefits vs adverse reactions to
drug
• Patient history
• Potential interactions of drug with other
medications
Planning
• Define goals: goal of drug therapy is to provide
maximum benefit with minimal harm.
• Establish Priorities: requires knowledge of drug
put together with patient’s unique history. 1st
priority is life threatening conditions and
reactions that cause acute discomfort that ends
in long-term harm
• Identifying interventions:
– Drug administration
– To enhance drug effectiveness
– To minimize adverse effects and interactions
– Patient education
• Establish criteria for evaluation: is drug working?
Implementation of care plan
– Drug administration
– Patient education
– Interventions to promote therapeutic effects
– Interventions to minimize adverse effects
Evaluation
– Therapeutic responses
– Adverse drug reactions and interactions
– Compliance to regimen
– Satisfactions with treatment
– How frequent do you evaluate??
• Depends on ….. ???
• Evaluation by lab tests- baseline data vs
current data