2. Contents:
1) Introduction to Biopharmaceutics
2) Absorption
3) Distribution
4) Metabolism
5) Elimination
6) Drug disposition
7) Bioavailability
8) Pharmacokinetics
9) Pharmacodynamics
10) Importance of Biopharmaceutics in dosage form design
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3. Introduction to Biopharmaceutics
• Biopharmaceutics is defined as the study of
factors influencing the rate and amount of drug
that reachesthe systemic circulation and the use
of this information to optimise the therapeutic
efficacy of drug products.
• It is the study of physiochemical properties
of the drugs, their proper dosage form in
which administered and the route of
administration as related to the onset,
duration and intensity of drug action.
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4. Absorption?
Definition:
• The process of movement of drug from its site
of administration to the systemic circulation is
called asabsorption.
• Theprocessof movement of unchangeddrug
from the site of administration to systemic
circulation.
• Absorption is the movement of the drug into
the blood stream.
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5. Distribution
Definition:
• The movement of drug between one
compartment and the other (generally blood and
the extra-vascular tissues) is referred to as drug
distribution.
• Distribution is the reversible transfer of a drug
from one location to another within the body.
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7. Elimination
Definition:
• Elimination is defined asthe process that tends to remove the
drug from the body and terminate itsaction.
• Elimination occurs by two processes-biotransformation
(Metabolism), which usually inactivates the drug, and
excretion which is responsible for the exit of drug or
metabolites from the body.
• Elimination = Biotransformation + Excretion
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11. Drug disposition
Definition:
• Any alternative in the drug’s bioavailability is reflected in
its pharmacological effects. Other processesthat play arole in
the therapeutic activity of a drug are distribution and
elimination. Together, they are known asdrug disposition.
• Processes that play a role in the therapeutic activity of a drug
are distribution and elimination. Together, they are known as
drug disposition.
• Drug disposition = Distribution + Elimination
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12. Bioavailability
• Bioavailability isdefined asthe rate andextent
(amount) of drugabsorption.
• The relative amount of an administration dose of a
particular drug that reaches the systemic circulation intact
and the rate at which this occurs is known as the
bioavailability.
• Thefraction of anadministration doseof the drug
that reaches the systemic circulation in the
unchangedform isknown asthe bioavailable dose.
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13. Pharmacokinetics
• The key pharmacokinetics was first introduced by
F.H.DOST in 1953.
• “Pharmacokinetics is the study of the kinetics of
absorption, distribution, metabolism and excretion
(ADME) of the drugs and their corresponding
pharmacologic, therapeutic or toxic response in animals
and man.”
• Simply Pharmacokinetics is the study of Absorption,
Distribution, Metabolism and Elimination (ADME) of
drug.
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14. Pharmacokinetics
• Pharmacokinetics is defined asthe study of time
course of drug ADME and their relationship
with its therapeutics and toxic effects of the
drug.
• Simply speaking, pharmacokinetics is the
kinetics of ADMEor KADME.
• Pharmacokinetic is a study of what the body
doesto the drug.
• Pharmacokinetics relates changes in
concentration of drug within the body with time
after its administration.
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15. Pharmacodynamics
• Pharmacodynamics is a study of what the drug does to the
body.
• Pharmacodynamics relates response to concentration of
drug in the body.
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16. Importance of Biopharmaceutics in
dosage form design:
• The above topic may be said that Biopharmaceutical and
Pharmacokinetic aspects in developing a dosage form.
• Dosage Form?
A drug is seldom given as such, it is developed into a
delivery system which is called as dosage form or drug delivery
system.
Development of a dosage form is aimed to deliver drug
concentration within therapeutic window ideally, without
fluctuations.
There are several types of dosage forms:
1. Immediate release
2. Modified release
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17. Immediate Release Dosage Forms
• Most conventional dosage forms are formulated to release
drug immediately after administration to obtain rapid and
complete systemic drug absorption.
• Conventional dosage forms
• Provide a fast onset of action.
• The tmax is short (early achievement of Cmax).
• Maintains concentration within therapeutic window for lesser
time.
• Thus, duration of action is small.
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18. Modified Release Dosage Form
• These are drug delivery systems which, by virtue of
formulation and product design, provide drug release in a
modified form distint from that of the conventional dosage
forms.
• They are defined by USP as those dosage forms whose drug
release characteristics of time course and / or location are
chosen to accomplish therapeutic objectives not offered by
conventional dosage forms.
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19. Most modified released systems fall into
following categories:
1. Delayed release
2. Extended release
a) Prolonged release
b) Sustained release
3. Targeted release
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20. 1. Delayed release
• Delayed release dosage forms release drug at a time later
than immediately after administration (i.e. there is a lag time
between a patient taking a medicine, and drug being detected
in the blood.
• Site-specific targeting is a type of delayed release which aims
to target specific regions of the GIT, e.g. the small intestine
or colon.
• Delayed release dosage forms contains one or more
immediate release units into a single dosage form.
• E.g. Enteric coated tablet
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21. 2. Extended release
• Extended release dosage form allows at least a
two-fold reduction in dosage frequency or
significant increase in patient compliance or
therapeutic performance as compared to an
immediate release (conventional) dosage form.
• It may be:
1) Prolonged release
2) Sustained release dosage forms
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22. a) Prolonged release dosage form
• Prolonged release drug delivery system, after a
single dose:
1) release drug slowly,
2) rate of absorption is slow,
3) thus with delayed onset of action and a
greater duration of action than a conventional
dosage form.
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23. b) Sustained release dosage form
• A sustained-release drug product is designed to release a
drug at a predetermined rate for the constant drug
concentration maintaining during a specific period of time.
• Sustained release DDS contains loading dose + maintenance
dose.
• Loading dose is immediately released to produce quick onset
of action.
• Maintenance dose is released at a controlled rate so that the
plasma concentration remains constant above MEC.
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24. 3. Targeted release dosage form
• A dosage form that releases drug at or near the
intended physiologic site of action.
• Targeted-release dosage forms may be have
either immediate- or extended-release
characteristics.
• E.g. colon targeting
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25. • Design of dosage form, the formulation of drug
product and the manufacturing process requires
a thorough understanding of the
biopharmaceutical principles &
pharmacokinetics of drug delivery.
• Biopharmaceutics is the study of the
interrelationship of the physicochemical
properties and in-vitro characteristics of the
drug and the dosage form on drug
bioavailabilty to produce a desired therapeutic
effect.
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26. Biopharmaceutical considerations in
design of dosage form:
• The prime considerations in the design of drug product
are therapeutic objectives, safety and efficacy.
• The finished drug product should meet the therapeutic
objective by delivering the drug with maximum
bioavailability and minimum adverse effects.
• The finished dosage form should not produce additional
side effects or discomfort due to the drug and/or
excipients.
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27. Essential elements of the
Biopharmaceutical considerations in
design of dosage form:
1) Studies done to decide the physiochemical nature of the
drug to be used i.e. salt, particle size.
2) The timings of these studies in relation to preclinical studies
with the drug.
3) The determination of solubility and dissolution
characteristics.
4) The evaluation of drug absorption & disposition studies.
5) The design & evaluation of the final drug formulation. 2
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28. References
1. “Biopharmaceutics & pharmacokinetics”, D.M.
Brahmankar & SunilB.Jaiswal,Vallabhprakashan.Page
No.1-4.
2. “Text book of Biopharmaceutics&pharmacokinetics”, Dr.
ShobharaniR.Hiramath.
3. “Applied Biopharmaceutics & pharmacokinetics”,
LeonShargel& AndrewB.C.
4. www.google.com 2
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29. Royal College of PharmaceuticalEducation &
Research, Malegaon 2
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