Transcript EO 003.01 - Part 15 - Basic Pharmacokinetics

Basic Pharmacokinetic Concepts
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EO 003.01 Part 15
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Importance of Lesson
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Pharmacy technicians are
required to have a basic
understanding of what the
body does to drugs in
order to understand the
factors that affect the
dosing of medications.
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Overview of Lesson
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Definitions
Absorption
Distribution
Metabolism
Excretion
Factors that influence drug dosage
and action
In-class Assignment
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Definitions
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Pharmacokinetics – what the body does
to the drug. Includes the following four
stages:
(1) Absorption of drug
(2) Distribution of the drug
(3) Metabolism of the drug
(4) Excretion of the drug
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Pharmacodynamics – what the drug
does to the body (will be covered in
future lectures).
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Topical
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Routes of Administration
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Intravenous
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Oral
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Subcutaneous
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Transdermal
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This will be covered in more detail during EO 003.02
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Absorption
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The process by which the drug
enters the body through the
bloodstream. Some substances
work outside the body but most
must enter the body in order to
work.
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Most drugs will undergo intestinal
absorption through the GI tract.
Drugs that are administered
intravenously are an exception as
they are directly administered to
the bloodstream and do not
undergo absorption.
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Absorption: Oral vs Intravenous Administration
Route
Benefits
Disadvantages
Oral
• Safe
• Convenient
• No need for sterile
equipment
• Variable absorption – only a
percentage of the drug
ingested is absorbed
• Gastric irritation may cause
vomiting (not useful if patient
is vomiting)
• Requires cooperation of
patient
• Onset of effect is slow
Intravenous
• Extremely rapid effect
• Initial absorption step is bypassed (immediately enters the
bloodstream)
• Drug levels are more
accurately controlled
• Most dangerous route
• Drug must be in aqueous
solution
• Must be performed slowly
• Once injected, drug cannot
be removed
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Distribution
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The movement of the drug from the
blood to the body tissue.
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Factors that effect drug movement in
body tissues include blood flow to the
tissue (i.e. organs = fast, muscle =
slow) as well as characteristics of the
drug.
Some characteristics include:
- Size of the drug
- Water solubility
- Lipid solubility
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Water-soluable vs Lipid soluable Medications
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Lipid soluble – the drug mixes well
with fats.
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If a drug is lipid soluble that means
that it can easily pass through the outer
membrane of a cell (which is
composed of lipids).
It also means that the drug will
distribute well into the fat tissue =
accumulation of drug in the body.
Water soluble – the drug mixes well
with water and as a general rule does
not mix well with fats.
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Metabolism
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Metabolism- the modification of the
chemical structure of a drug by the
body. There are MANY steps to this
process.
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Metabolite – drug product that results
from metabolism, may be more active
or less active than the original/parent
drug.
The majority of drug metabolism
occurs in the liver.
There are variations among individuals
as to how they metabolize medications
and how quickly they do so.
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Elimination
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Removal of the drug from the body.
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Main route for this to occur is through
the kidneys and excretion in the urine.
Some drugs may be reabsorbed via the
kidneys and will require multiple
metabolism steps before they can be
excreted from the body.
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Dosing of medications
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Dose = the amount of medication being
administered.
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Effective dose = dose of medication
required to achieve the desired
therapeutic effect.
Lethal dose = dose of medication that
will cause death.
If a effective dose and lethal dose do
not have much difference between
them that drug has a narrow
therapeutic range.
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Factors Influencing Drug Dosage
‫فکتورهایکه مقدار ادویه توصیه شده را متاثرمیسازد‬
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Age
Weight
Gender
Physical Health
‫سن‬
‫وزن‬
‫جنس‬
‫صحت فزیکی‬
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Age
‫سن‬
:‫شیر خوار‬
Infants:
‫ طفل نابالغ‬– Immature body systems
– Not fully developed kidney and ‫ سیستم کلیوی و کبد بشکل ممکن انکشاف ننموده‬‫است‬
liver functions
Children:
:‫اطفال‬
– Different physiologic profile and
‫ از نگاه فزیکی مختلف و دارای یک شکل‬body mass distribution
‫برجسته و با حجم خوبتر میباشد‬
– Dose per kilogram
‫ دوز ادویه بر کیلوگرام‬Older adults:
:‫جوان بزرک سال‬
– Depressed liver and kidney
‫ افسردگی کبد و سیستم کلیوی‬systems.
‫ افزائش تناسب مقدار انساج شهمی به انساج‬– Higher ratio of fat tissue to
muscle tissue
‫عضلی‬
– Increased risk for drug
‫ افزائش خطر مداخله ادویه‬interactions
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Weight
‫وزن‬
Children:
– Body surface area, height and weight
are important factors in determining
drug dosages
– Calculated by milligrams of drug per
kilogram of body weight
Adults:
– Overweight and underweight adults
– Average adult dose is based on a
drug quantity that will produce a
particular effect in 50% of the
population between 18 and 65 years
of age and approximately 150
pounds in weight.
– Dosage may need to be adjusted for
those who are extremely
underweight or overweight.
:‫اطفال‬
‫ طول و وزن از جمله‬،‫ قسمت سطحی وجود‬‫فکتور های مهم در تعین ادویه میباشد‬
‫ ملی گرام ادویه بر گیلوگرام وزن مریض‬‫محاسبه میگردد‬
:‫کاهالن‬
‫ کاهالن با وزن زیاد یا کم‬‫ دوز ادویه در سنین کاهالن متوسط براساس‬‫ فیصد تاثیرات خاص‬50 ‫مقدار ادویه بوده که‬
‫را‬
‫ تولید خواهد کرد و‬65 ‫ الی‬18 ‫دربین سنین‬
.‫ پاند باشد‬150 ‫تقریفا ً دارای وزن‬
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Gender
‫ارثیت‬
• Women higher percentage of body fat
• Men higher percentage of body fluid
• Drugs fat soluble, thus women may
accumulate more of these drugs in their
body
Pregnancy
• Drugs pass through the placenta and
breast milk.
• Very important to confirm if a patient
is pregnant and to make sure drugs are
dosed properly to prevent harm to the
developing baby or newborn.
‫فیصدی شهم در نزد زن ها بیشتر میباشد‬
‫فیصدی مایعات وجود در نزد مرد ها بیشتر است‬
‫ادویه منحل در شهم بدین معنی است که زن ها‬
‫مقدار بیشتراین ادویه را در وجود دارند‬
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‫ادویه از طریق پالسنتا و شیر ثدیه انتقال مینماید‬
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‫‪Physical health‬‬
‫صحت فزیکی‬
‫عبارت ازیک پروسه مرض بوده که نیازمندی های ‪Disease processes alter dosage requirements,‬‬
‫‪particularly in clients with kidney, liver,‬‬
‫مقدار ادویه توصیه شده را مخصوصا ً در مریضانیکه‬
‫‪digestive and cardiovascular problems.‬‬
‫مشکالت‬
‫کلیه‪ ،‬کبد‪ ،‬قلبی وعائی و سیستم هضمی داشته‬
‫باشند تغیرمیدهد‪،‬‬
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Questions?
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In-Class Assignment
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1. Put the following pharmacokinetic steps in the order in
which they generally occur:
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A)
B)
C)
D)
Metabolism
Elimination
Distribution
Absorption
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1. Put the following pharmacokinetic steps in the order in
which they generally occur:
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D) Absorption
C) Distribution
A) Metabolism
B) Elimination
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2. Answer: Which of the following is NOT true regarding
intravenous and oral administration?
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A) Intravenous administration
achieves a faster onset of action
when compared to oral.
B) If a person is vomiting oral
administration of medication is
preferred.
C) Oral administration is convenient
for the patient.
D) Intravenous administration skips
the absorption step as the drug is
administered directly into the
blood stream.
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3. Fill in the blanks: The majority of drug metabolism
occurs in the ______ and the majority of drugs are
eliminated via the _______.
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3. Answer: Fill in the blanks: The majority of drug
metabolism occurs in the liver and the majority of drugs
are eliminated via the kidneys.
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4. Which of the following is best defined as the dose which
achieves a desired therapeutic effect?
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A)
B)
C)
D)
Minimal dose
Maximal dose
Lethal dose
Effective dose
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4. Which of the following is best defined as the dose which
achieves a desired therapeutic effect?
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A)
B)
C)
D)
Minimal dose
Maximal dose
Lethal dose
Effective dose
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5. Which of the following influences the dosing of a drug?
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A)
B)
C)
D)
Gender
Weight
Age
All of the above
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5. Answer: Which of the following influences the dosing of
a drug?
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A)
B)
C)
D)
Gender
Weight
Age
All of the above
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