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ABSORPTION OF DRUGS
FIRST M.PHARMACY 2017-2019,
DEPARTMENT OF PHARMACEUTICS,
COLLEGE OF PHARMACY
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CONTENTS
➢DEFINITION
➢ INTRODUCTION
➢ STRUCTURE OF CELL MEMBRANE
➢MECHANISM OF DRUG ABSORPTION.
➢ FACTORS AFFECTING ABSORPTION
▪ PHYSIO-CHEMICAL FACTORS
▪ PHARMACEUTICAL FACTORS
➢DOSAGE FORMS
➢REFERENCES
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INTRODUCTION OF ABSORwwPw.DuTloMixI.coOm N
Definition:
➢ Absorption can also be defined as the process of
movement of unchanged drug from the site of
administration into the systemic circulation.
➢ Concentration can be measured more accurately in
plasma.
In drug absorption two parameters are frequently used.
➢ Magnitude of drug that reaches the systemic
circulation
➢ Rate at which the drug is absorbed.
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CELL MEMBRANE STRUCTURE
➢ Also called the plasma membrane, plasmalemma or
phospholipid bilayer.
➢ The plasma membrane is a flexible yet sturdy
barrier that surrounds & contains the cytoplasm of
a cell.
➢ Cell membrane mainly consists of:
Lipid bilayer-phospholipid
-Cholesterol
-Glycolipids.
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2. Proteins -Integral membrane proteins
-Lipid anchored proteins
-Peripheral Proteins
➢ Hydrophobic core of the membrane is
responsible for the relative impermeability of
polar molecules.
➢ GI lining constituting the absorption barrier
allows most nutrients like glucose, amino acids,
fatty acids, vitamins, etc.
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LIPID BILAYER 7
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▪The basic structural framework of the plasma
membrane is the lipid bilayer.
▪Consists primarily of a thin layer of amphipathic
phospholipids which spontaneously arrange so that
the hydrophobic “tail” regions are shielded from
the surrounding polar fluid, causing the more
hydrophilic “head” regions to associate with the
cytosolic & extracellular faces of the resulting
bilayer.
▪This forms a continuous, spherical lipid bilayer
approximately 7nm thick.
GASTRO INTESTINAL TRACT
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➢ STOMACH : www.DuloMix.com
➢ The surface area for absorption of drugs is
relatively small in the stomach due to the absence
of macrovilli & microvilli.
➢ Extent of drug absorption is affected by variation in
the time it takes the stomach to empty, i.e., how
long the dosage form is able to reside in stomach.
➢ Stomach emptying applies more to the solid dosage
forms because the drug has to dissolve in the GI
fluid before it is available for absorption.
➢ Since solubility & dissolution rate of most drugs is
a function of pH.
SMALL INTESTINE :
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➢The drugs which are predominanwwtwl.DyuloMixa.cobm sorbed
through the small intestine, the transit time of a
dosage form is the major determinant of extent of
absorption.
➢Various studies to determine transit time:
▪ Early studies using indirect methods placed the
average normal transit time through the small
intestine at about 7 hours.
▪ These studies were based on the detection of
hydrogen after an oral dose of lactulose.
(Fermentation of lactulose by colon bacteria yields
hydrogen in the breath).
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➢Newer studies suggest the transit time to be about 3
to 4 hours.
➢Use gamma scintigraphy.
➢Thus, if the transit time in small intestine for most
healthy adults is between 3 to 4 hours, a drug may
take about 4 to 8 hours to pass through the stomach
& small intestine during fasting state.
➢During the fed state, the small intestine transit time
may take about 8 to 12 hours.
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▪ LARGE INTESTINE : www.DuloMix.com
▪ The major function of large intestine is to absorb
water from ingestible food residues which are
delivered to the large intestine in a fluid state, &
eliminate them from the body as semi solid feces.
▪ Only a few drugs are absorbed in this region.
Mechanism of drug absorption
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There are three main mechanisms of drug transport across
the gastrointestinal epithelium.
➢ Trans cellular, i.e., Across the cells
▪ Passive transport
▪ Active transport
➢ Para cellular, i.e., Between the cells Pore transport
▪ Permeation through tight junctions of epithelial cells
▪ Persorption
➢ Vesicular i.e., Within the vesicles into cells.
▪ Pinocytosis
▪ Phagocytosis
TRANSCELULAR /INTRACELLULAR 13
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The passage of the drugs across the GI epithelium is
the common pathway for the drug transport.
3 steps:
➢ Permeation of GI epithelial cell membrane, a
lipoidal barrier is the major obstacle to drug
absorption.
➢ Movement across the intracellular space
(cytosol).
➢ Permeation of the lateral or baso lateral
membrane .
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Passive transport process
➢ Passive diffusion
➢ Carrier mediated transport
➢ Facilitated diffusion
➢ Ion pair transport
Passive Diffusion 15
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▪ It is defined as the
difference in the drug
concentration on either
side of the membrane.
▪ Also called nonionic
diffusion
▪ It is the major process for
absorption of more than
90% of the drugs.
▪ The driving force for this
process is the
‘concentration or
electrochemical gradient’.
➢ Expressed by Fick’s first law of diffusion – 16
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“The drug molecules diffuse from a region of higher
concentration to one of lower concentration until
equilibrium is attained & the rate of diffusion is
directly proportional to the concentration gradient
across the membrane”.
dQ = D A Km/v (CGIT – C)
dt h
Cntd…
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Where, www.DuloMix.com
dQ/dt = Rate of diffusion (Amount/time)
D = Diffusion co efficient of the drug
through the membrane( Area/time)
A = Surface area of the absorbing membrane
for drug diffusion(Area)
Km/w = Partition co efficient
Cgit – C = Concentration gradient
h = Thickness of the membrane
Pore Transport
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▪It is also called as Convective transporwtw,w .BDulouMilx.kcom flow
or filtration.
▪Mechanism – Protein channels present in the cell
membrane.
▪The driving force for this process is the ‘hydrostatic
pressure or the osmotic differences across the
membrane’.
▪The process is important in the absorption of low
molecular weight (less than 100), low molecular
size drugs.
▪Example: Urea, Water, Sugar
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➢ The rate of absorption via pore transport depends on the
number & size of the pores, & given as follows:
dc = N. R2. A . ∆C
dt (η) (h)
where,
dc /dt = rate of the absorption.
N = number of pores
R = radius of pores
∆C = concentration gradient
η = viscosity of fluid in the pores
Ion-pair transport
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▪Some agents penetrate the membrane by forming
reversible neutral complexes with endogenous ions of
the GIT like mucin.
▪Such neutral complexes have both the required
lipophilicity as well as aqueous solubility for passive
diffusion. Such phenomena is called ion-pair transport.
▪Quaternary ammonium compounds and sulfonic acid
which ionized under all pH conditions.
Eg. Propranolol, a basic drug forms an ion pair with 21
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oleic acid
Carrier-mediated transport
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▪The mechanism is thought to involve a component of the
membrane called as the carrier that binds reversibly or non-
covalently with the solute molecules to be transported.
▪The carrier may be an enzyme or some other component of
the membrane.
▪Two types
▪Facilitated diffusion
▪Active transport
Facilitated diffusion 2 323
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➢ This mechanism energy production.
involves the driving ➢ Eg. Vitamin B12.
force is concentration
gradient.
➢ In this system, no
expenditure of energy is
involved (down-hill
transport), therefore the
process is not inhibited
by metabolic poisons
that interfere with
Active transport
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➢ Transport processes
require energy from
ATP to move drug
molecules from
extracellular to
intracellular milieu.
➢It is process where the
materials are transported
across membranes against
a concentration gradient.
➢The drug is transported from a region of lower to
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one of higher concentration i.e.. againswtw wt.DhuloeMi x.com
concentration gradient or ‘uphill transport’.
➢Examples : Sodium, potassium, iron, glucose and
vitamins like niacin, pyridoxine and ascorbic acid.
Types
➢ Primary active transport –Uni port
❖ Ion transporters
❖ ABC (ATP – binding cassette ) transporters -Eg. p
Glycoprotein. MDR.( Multi drug resistance)
➢ Secondary active transport
❖ Symport (co -transport)
❖ Antiport (counter -transport)
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Paracellular/Intercellular Transport
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➢ It is defined as the transport of dwwrw.DuulgoMsix.comthrough the
junctions between the GI epithelial cells. This pathway is
of minor importance in drug absorption. The two
paracellular transport mechanisms involved in drug
absorption are –
➢Permeation through tight junctions of epithelial cells –
this process basically occurs through openings which are
little bigger than the aqueous pores. Compounds such as
insulin and cardiac glycosides are taken up this
mechanism.
➢Persorption – is permeation of drug through temporary
openings formed by shedding of two neighbouring
epithelial cells into the lumen.
Endocytosis 28
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➢Also called Corpuscular or Vesicular transport
➢It involves engulfing extracellular materials within a
segment of the cell membrane to form a saccule or a
vesicle which is then pinched-off intra cellularly.
➢Includes two type of process:
▪Phagocytosis (cell eating): adsorptive uptake of solid
particulates, and
▪ Pinocytosis (cell drinking): uptake of fluid solute.
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Phagocytosis
Pinocytosis
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➢This process is important in the absorption of
oil soluble vitamins & in the uptake of nutrients.
FACTORS AFFECTING DRUG
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ABSORPTION www.DuloMix.com
(a)PHARMACEUTICAL FACTORS
▪Physicochemical Factors
▪Dosage form characteristics
(b)PATIENT RELATED FACTORS
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Physicochemical factors
➢Lipid solubility ,dissociation constant and pH
➢Dissolution
➢Salt form
➢Particle size and Effective surface area
➢Polymorphism and Amorphism
➢Solvates and hydrates(Pseudopolymorphism)
➢Drug permeability and absorption
➢Viscosity
Lipid solubility and dissociation
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constant and pH www.DuloMix.com
More the drug in non ionized form , more is it lipid
soluble and better is the absorption.
pH partition hypothesis
The interrelationship of dissociation
constant, lipid solubility ,pH at the absorption site
and absorption characteristics of various drugs
throughout the GIT.
▪The pH partition theory is the process of drug
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absorption from the GIT and its distribwwuw.tDiulooMnix.c oam cross
all biological membrane.
▪ The theory states “ That for the drug compound of
molecular weight greater than 100 , which are
primarily transported across the bio membrane by
passive diffusion , the process of absorption is
governed by
➢ Dissociation constant
➢ Lipid solubility
➢ pH at the absorption site
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The rate of losss of drug in solution form from the
absorption site is given by:
-DCt/dt=KaCu
Where,
Dct/dt= rate of drug loss from absorption site
Ka = absorption rate constant
Ct =Total drug concentration
Cu = concentration of unionized drug.
The dissociation constant is expressed for both acids 36
and bases as a pKa value: www.DuloMix.com
➢FOR ACID
pH= pKa+log conc.(ionized)/conc.(unionized)
➢FOR BASE
pH= pKa+log conc.(unionized)/conc.(ionized)
Weakly acidic drugs (Eg :Aspirin) dissolve faster in
gastric fluids.
Weakly basic drugs (Eg :Quinine) dissolve faster in
intestinal fluids.
Acidification or basification of both stomach and
intestine will produce converse effects.
➢Though the pH partition hypothesis simplified the
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concept of drug absorption, it has its owwww.nDul oMliix.mcomitations
Deviations from this theory include
➢(a)presence of virtual membrane pH
➢(b)absorption of ionized drug
➢(c) GI surface area and residence time of drug
➢(d)presence of aqueous unstirred diffusion layer.
Dissolution
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▪A drug gets absorbed in the biological sywswtwe.DumloMix,. cowm hen it
gets dissolved in the physiological fluid at the
absorption site.
Solid dosage form(tablet or capsule)
Disintegration(coarse particles of drug)
Dissolution
Drug in solution(very fine particles)
Drug in systemic circulation
Dissolution 39
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▪Based on permeability and solubility BCS
CLASSIFICATION have developed
Class 1-↑ soluble ↑ permeable Eg. Diltiazem
Class 2-↓ soluble ↑ permeable Eg. Nifidifin
Class 3-↑ soluble ↓ permeable Eg. Insulin
Class 4-↓ soluble ↓ permeable Eg. Taxol
Theories of drug dissolution 41
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➢Diffusion layer model/film theory
➢Danckwert’s model/surface renewal theory
➢Interfacial model/double barrier model theory
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Diffusion layer model/film wtwwh.DueloMoix.corm y
Noyes-whitney equation
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➢Dissolution under sink condition is a
1st order process ➢ where dC/dt is the rate of
dissolution
Dc ➢ D is the diffusion coefficient of
= K (Cs-Cb) the drug in solution in G.I. fluid
➢ S is the effective surface area of
Dt
drug particle in contact with the
G.I fluid,
➢ Cs is the saturation solubility of
the drug in the diffusion layer
and
➢ Ct is the concentration of drug in
solution in the bulk medium (G.I
fluid).
Modified Noyes-whitney’s equation 44
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❑ The Noyes Whitney Equation Was Modified By
Nernst And Brunner As Follows:
dc = DAKw/o (Cs – Cb )
dt Vh
Where,
D= diffusion coefficient of drug.
A= surface area of dissolving solid
Kw/o= water/oil partition coefficient of drug.
V= volume of dissolution medium.
h= thickness of stagnant layer.
(Cs – Cb )= conc. gradient for diffusion of drug.
Danckwert’s model/penetration or
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surface renewal theory www.DuloMix.com
▪
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INTERFACIAL BARRIER MODEL/DOUBLE
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BARRIER OR LIMITEwwDw.DuloMix.com
SOLVATION THEORY
The concept of this theory is explained by following
equation-
G = Ki (Cs – Cb)
Where,
G = dissolution rate per unit area,
Ki = effective interfacial transport constant.
Salt form
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➢Conversion of a weakly acidic or basic drug in its salt
form enhances the solubility and dissolution rate of
the drug.
➢For salts of weak acids,
[H]d>[H]b
➢For salts of weak bases,
[H]d<[H]b
Where,
➢[H]d=hydrogen ion conc. of diffusion layer
➢[H]b= hydrogen ion conc. of bulk layer
Cont…
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➢The increase and decrease in the pH of diffusion
layer by salts of weak acids and weak bases has
been attributed to the buffering action of strong
base cation and strong acid anion.
➢Weakly acidic drug- strong base salt
Eg. Na, K salts of barbiturates,sulphonamides
➢Weakly basic drug- strong acid salt
Eg. Hcl,SO4 salts of alkaloidal drugs.
Particle size and surface area
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➢Particle size and surface area are an inversew wrwe.DlulaoMtixi.ocomnship.
➢Surface area can be classified as
(1)Absolute surface area
(2)Effective surface area
➢Greater the effective surface area, better the dissolution and so
the absorption.
➢Absolute surface area can be converted to effective surface
area by :
(1)Use of surfactants like Polysorbate 80.
(2)Adding hydrophillic diluents like PEG,PVP etc.
➢ Effective surface area α dissolution rate
Eg. Griseofulvin, Tetracycline and chloramphenicol
Cont… 51
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Exception – Micronisation of hydrophobic drugs
results in ↓effective surface area ↓dissolution rate
Eg . Aspirin, Phenobarbital, Phenacetin.
Micronisation not recommended
-unstable & degrade eg. penicillin
-undesirable effect eg. GI irritation by
nitrofurantoin
-when sustained effect is desired
Polymorphism and amorphism
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▪POLYMORPHISM
-Substances exist in more than one crystalline form
-Definite structural arrangements
-Different physical properties Density, Melting point,
Boiling point, solubility.
▪Two types
Enantiotropic-reversible-altering temperature Eg.Sulphur
Monotropic- unstable at all temp.& pressure
Eg. Glyceryl stearates
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INTERNAL STRUCTURE OF A
COMPOUND
CRYSTALLINE
AMORPHOUS
NON STOICHOMETRIC
MOLECULAR
POLYMORPHS
ADDUCTS
STOICHOMETRIC(PSEUDOPOLYMORPHS)
ENANTIOTROPIC MONOTROPS
ORGANIC
HYDRATES
SOLVATES
Cont…
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▪STABLE – ↑Melting point ↓energyww w↓.DsulooMilx.ucombility
▪METASTABLE- ↓Melting point ↑energy
↑ solubility ↑ bioavailability
▪AMORPHISM
-No internal crystal structure.↑ aqueous solubility
Eg. Novobiocin-amorphous form 10 times more
soluble than crystalline form.
Dissolution- Amorphous>meta stable >Stable
Hydrates and solvates
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SOLVATES
➢Adducts where solvent molecule incorporated in
crystal lattice of solid
➢High solubility
➢Eg. Solvates of Cortisone , Griseofulvin
HYDRATES
➢If solvent is water – called as hydrate
➢Anhydrous forms more soluble than hydrates
➢Eg. Anhydrous ampicillin , Theophylline
Drug permeability and absorption
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➢Most orally administered drugs enter the systemic
circulation by passive diffusion
➢Three major characters that determine the
permeability of the drug across the intestinal
epithelium are:
(A) Lipophilicity of the drug
(b) Polarity
(c) Molecular size
➢The net effect of above three properties is given as
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RULE OF FIVE by Lipinski which is written as:
Molecular weight of drug <=500
Lipophilicity of drug <=5
Number of H-bond receptors <=10
Number of H-bond donors <=5
❑If any two of these values are greater than
specified limits, the oral absorption of a drug may
be a significant problem.
Drug stability 58
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▪ A drug for oral use may destabilized either during
its shelf life or in the GIT. Two major stability
problems resulting in poor bioavailability of an
orally administered drug are -degradation of the
drug into inactive form, and interaction with one or
more different component(s) either of the dosage
form or those present in the GIT to form a complex
that is poorly soluble or is unabsorbable.
Pharmaceutical factors
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➢Disintegration time
➢Dissolution time
➢Manufacturing and processing variables
▪ Method of granulation
▪ Compression force
➢Pharmaceutical ingredient/excipients
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Disintegration time www.DuloMix.com
➢Rapid disintegration is important to have a rapid
absorption so lower disintegration time is required.
➢Disintegration time of tablet is directly
proportional to –amount of binder and compression
force.
➢It is important to note that in vitro disintegration
test gives no means of a guarantee of drugs B.A.
because if the disintegrated drug particles do not
dissolve then absorption is not possible.
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Dissolution time:
➢Dissolution is a process in which a solid substance
solubilises in a given solvent ie… mass transfer
from the solid surface to the liquid phase.
➢Dissolution time is also an important factor which
affect the drug absorption .
Manufacturing variables: 62
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➢Several manufacturing processes influence drug
dissolution from solid dosage forms.
For example: For tablet it is
➢Method of granulation
➢Compression force
Method of granulation:
➢ Different methods like wet granulation , dry
granulation and direct compression etc. yields
product with different dissolution.
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▪Compression force
The compression force employed in tableting
process influence density, porosity, hardness,
disintegration time and dissolution rate of tablets.
Pharmaceutical
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ingredients/excipients:
▪More the number of Excipients in the dosage form,
more complex it is & greater the potential for absorption
and Bioavailability problems.
▪A) Vehicle
▪Rate of absorption – depends on its miscibility with
biological fluid.
▪Miscible vehicles (aqueous or water miscible vehicle)
causes rapid absorption e.g. propylene glycol.
▪Immiscible vehicles – Absorption depends on its
partitioning from oil phase to aqueous body fluid.
B) Diluents
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▪Hydrophilic diluents – Imparts Absorptwiwow.DnuloMix.com
▪Hydrophobic diluents – Retards Absorption
▪Also, there is a drug-diluent interaction, forming
insoluble complex and retards the absorption. E.g.
Tetracycline-DCP
C) Binders & granulating agent –
▪Hydrophilic binders – Imparts hydrophilic properties
to the granule surface – gives better dissolution
properties of the poorly wettable drugs. E.g. Starch,
Gelatin. PVP.
▪But more amount of binder increases the hardness of
the tablet and retards the absorption rate.
D) Disintegrants 66
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▪Mostly hydrophilic in nature.
▪Decrease in amount of disintegrants – significantly lowers
B.A.
E) Suspending agents/viscosity agent
▪Stabilized the solid drug particles and thus affect drug
absorption.
▪Macromolecular gum forms un-absorbable complex with
drug e.g. Na CMC.
▪Viscosity imparters – act as a mechanical barrier to
diffusion of drug from its dosage form and retard GI transit
of drug.
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G) Surfactants
▪May enhance or retards drug absorption by
interacting with drug or membrane or both.
▪Physiologic surfactants – bile salts – promotes
absorption – e.g. Griseofulvin, steroids
▪It may decrease absorption when it forms the un-
absorbable complex with drug above CMC.
H) Coating 68
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▪In general, deleterious effects of various coatings on the
drug dissolution from a tablet dosage form are in the
following order.
▪Enteric coat > sugar coat > non-enteric coat.
▪The dissolution profile of certain coating materials change
on aging; e.g. shellac coated tablets.
F) Lubricants
▪Commonly hydrophobic in nature – therefore inhibits
penetration of water into tablet and thus dissolution and
disintegration.
I) Buffers
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▪Buffers are sometimes useful in creatinwgww .tDhuloeMix .croimght
atmosphere for drug dissolution as was observed for
buffered aspirin tablets.
▪However, certain buffer systems containing
potassium cations inhibit the drug absorption as seen
with Vitamin B2 and sulfanilamide.
J) Colourants
▪Even a low concentration of water soluble dye can
have an inhibitory effect on dissolution rate of
several crystalline drugs.
▪The dye molecules get absorbed onto the crystal
faces and inhibit the drug dissolution. For example:
Brilliant blue retards dissolution of sulfathiazole.
Nature and type of dosage form 70
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▪Apart from the proper selection of the drug, clinical
success often depends to a great extent on the proper
selection of the dosage form of that drug.
▪As a general rule, the bio-availability of a drug form
various dosage forms decrease in the following order:
Solutions > Emulsions > Suspensions > Capsules >
Tablets > Coated Tablets > Enteric Coated Tablets >
Sustained Release Products.
Product age and storage conditions:
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▪Product aging and storage conditions can adversely
affect the bio-availability by change in especially the
physico-chemical properties of the dosage forms.
▪For example:
▪ Precipitation of the drug in solution
▪ Hardening of tablet
▪Change in particle size of suspension.
Dosage forms 72
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➢ Order of bioavailability of drugs.
➢ Solutions>suspensions>capsules>tablets>coated
tablets
SOLUTIONS
➢ Drugs absorbed more rapidly in this form.
➢ When this formulation is taken after meal gastric
emptying is the rate limiting step.
Factors influencing are
➢ Nature of the solvent viscosity, surfactant,
solubilisers, stabilizers.
➢ Drugs which are poorly soluble can be converted
to water soluble by the addition of co solvents
such as alcohol, propylene glycol, polyethylene
glycol 400 etc…
Suspensions
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➢Dissolution is the rate limiting step forw wtwh.Deulo Mix.com
absorption the drug from suspension.
Factors to considered are
➢ Particle size ,
➢ Inclusion of wettings ,
➢ Formation of insoluble complex,
➢ Crystal form & viscosity.
Capsules
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▪For hard gelatin capsules the shell should disrupt
quickly and expose the contents to the GI fluids.
▪Factors influencing are particle size, density, crystal
form of the drug, selection of diluents.
▪For hydrophobic drugs with a fine particle size in
capsule results in decrease in porosity of the powdered
drug and thus decreased penetrability by the solvent
which results clumping of particle.
▪soft elastic capsule dissolve faster than hard gelatin
capsule & tablets. Which shows better bioavailability
from oily solutions, emulsions, or suspensions.
Tablets 75
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▪This is the most widely used dosage form.
▪Problem with this arises from reduction in the ESA
due to granulation& subsequent compression in to
dosage form.
▪Tablet disintegration and granule disintegration are
the important steps in absorption process.
▪Compression force also may be an important factor.
▪Disintegration is the rate limiting step for this.
Coated tablets
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➢Coat is generally used to mask unpleawswaw.nDultoM tix.acosmte &
odor & to protect the ingredients from decomposition
during storage.
➢This adds an additional barrier between GIT & drug.
It should get dissolve before tablet disintegration &
dissolution.
Sugar & film coatings
➢Sugar coating will take more time than film coating.
➢Ex: methyl cellulose which retards the dissolution
➢Now a days film and press coated are mostly used.
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Enteric coated tablets www.DuloMix.com
➢It is a special film coated design to restricts the
gastric fluids & to dissolve in small intestine.
➢Protect the drug from the degradation in the
stomach Ex: erythromycin.
➢Minimize the gastric distress caused by some
drugs. Ex: aspirin.
➢These tablets must empty the stomach before the
drug absorption can begin.
➢The polymers with pka values ranging from 4-7
have been found to use.
➢Thickness of coating will effects the bioavailability
in these formulations.
In vitro correlation of drug absorption79
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DISINTEGRATION TESTS
➢It is provided to determine ➢For un coated tablet and
the compliance with the limit capsules the time is 30 mins.
on disintegration stated in where as for coated tablet it
the individual monograph. is 2 hrs.
➢Exception is soft gelatin
capsule.
➢Formulation tested are
un coated tablet, plain
coated, enteric coated, buccal,
sub lingual, hard gelatin
capsule.
DISSOLUTION TESTS
➢The development of this test predicts the drug 80
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absorption.
➢It shows close relation b/w drug absorption and
dissolution rather than disintegration.
➢By using USP apparatus
Type1- basket method
Type2- paddle method
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➢Basket method- the basket containing tab and
capsules are immersed in the dissolution fluid and
rotated .
➢Paddle method-the dosage form is placed directly in
the dissolution medium and paddle is rotated.
➢Fluids may be water , HCL, buffer maintained at
370c.
➢The samples are removed at desired interval and
assayed for drug content.
REFERENCES
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➢ D.M. Brahmankar, S.B. Jaiswal; “Bio pharmaceutics
& Pharmacokinetics”; first edition, 12th reprint;
Vallabh Prakashan;
➢ Milo Gibaldi ; “Bio pharmaceutics and clinical
pharmacokiceutics “ fourth edition , PharmaMed
Press.
➢ “Clinical pharmacokinetics ,concepts and
applications “ 3 rd edition by MalcomRowland and
Thom N .Tozer ,Lea febiger.
➢ “Applied Bio pharmaceutics & Pharmacokinetics”
by Shargel ,Land YuABC, 2 nd edition.
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