4. Therapeutic success of a
rapidly & completely
absorbed drug.
Minimum effective conc.
Therapeutic failure of a
slowly absorbed drug.
Subtherapeutic level
Time
Plasma
Drug
Conc.
Not only the
magnitude of drug
that comes into the
systemic circulation
but also the rate at
which it is absorbed
is important this is
clear from the figure.
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 44
9. IItt ccoonnssiissttss ooff ttwwoo bbaacckk ttoo bbaacckk llaayyeerrss mmaaddee uupp ooff
tthhrreeee ttyyppeess:: PPhhoosspphhoolliippiidd,, CChhoolleesstteerrooll,, GGllyyccoolliippiiddss..
11)) PPhhoosspphhoolliippiiddss ::
Principal type of lipid in
membrane about 75 %.
Contains polar and non polar
region.
Polar region is hydrophilic and
non polar region is hydrophobic.
Non polar head contain two fatty
acid chain.
One chain is straight fatty acid
chain.( Saturated )
Another tail have cis double bond
and have kink in tail.
( Unsaturated )
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 99
44. Diagram Representing Absorption, Distribution, Metabolism
and Excretion
The ultimate goal is to have the drug reach the site of action in
a concentration which produces a pharmacological effect. No
matter how the drug is given (other than IV) it must pass
through a number of biological membranes before it reaches
the site of action.
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 4444
67. pH Membrane Blood Supply Surface Area Transit Time By-pass liver
BUCCAL approx 6 thin Good, fast
absorption with
low dose
small Short unless
controlled
yes
ESOPHAGUS 6 Very thick, no
absorption
- small short -
STOMACH 1 – 3 Normal
Lipophilic,acidic
and neutral drugs
good small 30 - 40 minutes,
reduced absorption
no
DUODENUM 5 – 7 Normal
Mainly lipohilic
and neutral drugs
good large very short (6"
long)
no
SMALL
INTESTINE
6 -7 Normal
All types of drugs
good very large 10 - 14
ft, 80 cm 2 /cm
about 3 hours no
LARGE
INTESTINE
6.8 - 7 - good not very large 4 -
5 ft
long, up to 24 hr lower colon,
rectum yes
Gastrointestinal (GI) Physiology
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 6677
69. INFLUENCE OOFF DDRRUUGG ppKKaa AANNDD GGII PPHH OONN
DDRRUUGG AABBSSOORRBBTTIIOONN
Drugs Site of absorption
Very weak acids (pKa > 8.0) Unionized at all ph values
Absorbed along entire length of GIT
Moderately weak acids (pKa 2.5 – 7.5) Unionized in gastric ph
Ionized in intestinal ph
Better absorbed from stomach
Strong acids (pKa <2.5) Ionized at all ph values
Poorly absorbed from git
Very weak bases (pKa < 5) Unionized at all ph values
Absorbed along entire length of GIT
Moderately weak bases (pKa 5 – 11 ) Ionized in gastric ph
Unionized in intestinal ph
Better absorbed from intestine
Strong bases (pKa >11) Ionized at all ph values
Poorly Absorbed from GIT
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 6699
72. FFaaccttoorrss aaffffeeccttiinngg GGaassttrriicc EEmmppttyyiinngg
Volume of
Ingested Material
As volume increases initially an increase then a
decrease. Bulky material tends to empty more slowly
than liquids
Type of Meal Gastric emptying rate:
carbohydrates > proteins > fats
Temperature of
Food
Increase in temperature, increase in emptying rate
Body Position Lying on the left side decreases emptying rate and right
side promotes it
Git PH Retarded at low stomach PH and promoted at higher
alkaline PH
Emotional state Anxiety promotes where as depression retards it
Disease states gastric ulcer, hypothyroidism retards it, while duodenal
ulcer, hyperthyroidism promotes it.
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 7722
75. PHYSICAL FACTORS
1. PARTICLE SIZE
Smaller particle size, greater surface area then higher will be
dissolution rate, because dissolution is thought to take place at
the surface area of the solute( Drug).
This study is imp. for drugs that have low aqueous solubility.
Absorption of such drugs can be increased by increasing particle
size by Micronization.
ex. Griseofulvin, active intravenously but not
effective when given orally.
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 7755
76. 1. PARTICLE SIZE
To poor soluble drug, disintegration agents and surface active
agents may be added .
• ex. Bioavailability of Phenacetin is increased by tween 80.
Micronization also reduces the dose of some drugs
• ex. the dose of griseofulvin is reduced to one half while the dose
of spironolactone is reduced to one twentieth.
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 7766
77. Lesser particle size is always not helpful
Ex. Micronization of Aspirin, phenobarbital, lesser effective
surface area and hence lesser dissolution
rate
Reasons:
On their surface, hydrophobic drugs absorb air and reduce
their wettability
Particle having size below 0.1 micron reaggregate to form
large particle
Particle having certain micro size get electrical charge which
preventing c 0088//1100//22001100 ontact with wetKKtLLiEEnCCgOO PPm,, NNeiippdaanniiium 7777
78. Finally drug size reduction and subsequent increase in
surface area and dissolution rate is always not useful.
Ex. of such drugs are Penicillin G & Erythromycin
These Drugs are unstable and degrade quickly in solution.
Sometime, reduction in particle size of nitrofurantoin and
piroxicam increase gastric irritation
These problem can be overcome by Microencapsulation.
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 7788
79. 2. Crystal Form
Substance can exist either in a crystalline or amorphous form.
When substance exist in more than one crystalline form, the
different form are called polymorphs and the phenomena as
polymorphism .
Two types of Polymorphism
1) Enantiotropic polymorph ex. Sulfur
2) Monotropic polymorph ex. Glyceryl Stearates
Polymorphs have the same chemical structure but different
physical properties such as solubility, density, hardness etc.
ex. Chlormphenicol has a several crystal form, and when given
orally as a suspension, the drug concentration in the body was
found to be dependent on the percentage of β - polymorph in
the suspension. The form is more soluble and better absorbed.
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 7799
80. One of the several form of polymorphic forms is more stable
than other. Such a stable form having low energy state and high
melting point and least aqueous solubility
The remaining polymorphs are called as metastable forms
which have high energy state, low melting point and high
aqueous solubilities.
About 40% of all organic compounds exhibit polymorphism.
Some drug exists in amorphous form which have no internal
crystal structure. Such drugs have high energy states than
crystal form hence they have greater aqueous solubility than
crystalline form.
Ex. Novobiocin, cortisone acetate.
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 8800
81. 3. Solvates And Hydrates
Many drugs associate with solvent and forms solvates
Solvent is water then it is called as hydrate
eg. Anhydrous form of caffeine and theophylline dissolve more
rapidly than hydrous form of these drugs.
Solvate form of drugs with org. solvent may dissolve fast in water
than non solvated form. eg. Fluorocortisone
4. Complexation
This property can influence the effective drug concentration in gi
fluids. Complexation of drug and gi fluids may alter the rate
and extent of absorption
eg. Intestinal Mucin form complex with Streptomycin and
Dihydro Streptomycin.
In some cases, Poor water soluble drugs can be administered as
water soluble complexes. eg. Hydroquinone with Digoxin.
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 8811
82. 5.Adsorption
It is a physical and surface phenomena where the drug
molecules are held on the surface of some inert substances by
vanderwall’s forces.
ex. Charcoal used as an antidote; When it is co-administered with
promazine, then it reduces the rate and extent of absorption
Cholestyramine reduces the absorption of warfarin.
6.Drug Stability And Hydrolysis In GIT
Drugs undergoes various reactions due to wide spectrum of ph
and enzymatic activity of GI fluid namely acid and enzymatic
hydrolysis.
eg. T½ of Penicillin G= 1 min. at pH 1
T½ of Penicillin G= 9 min. at pH2
So it means Penicillin G is stable at less acidic pH
Erythromycin and its esters are unstable at gastric fluid (T½=Less than 2 min.)
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 8822
83. 7. Salts
Na or K salts of weak acid dissolves rapidly than free acid.
ex. Na salts of Novobiocin shows improved bioavailability
Certain salts also may have low solubility and dissolution rate.
ex. Al salts of weak acid and pamoate salt of weak base
8. Presence Of Surfactant
Use of wetting agent and Solubilizing agent improve the Dissolution
rate & absorption of drugs.
Ex. Tween 80 increase the rate & extent of absorption of Phenacetin.
9. Dissolution
Disintegration is the formation of dispersed granules from an
intact solid dosage form whereas the dissolution is the formation
of solvated drug molecules from the drug
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 8833
84. SOLID DRUG
DISSOLUTION
DRUG AT ABSORPTION
SITE
ABSORPTION
DRUG IN
SYSTEMIC
CIRCULATION
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 8844
85. NOYES AND WHITNEY’S EQUATION
dc/dt = KS(CS-C)
Where,
dc/dt = Rate constant, K = constant, S = surface area
of the dissolving solid, Cs=solubility of the drug in the
solvent, C=concentration of drug in the solvent at time t.
Constant K=D/h
Where, D is the diffusion coefficient of the dissolving
material and h is the thickness of the diffusion layer
Here, C will always negligible compared to Cs
So,
dc/dt=DSCs/h
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 8855
86. PPHHYYSSIICCOOCCHHEEMMIICCAALL FFAACCTTOORRSS
1) pH PARTITION THEORY (Brodie) :
It explain drug absorption from GIT and its distribution across
biomembranes.
Drug(>100 daltons) transported by passive diffusion depend
upon:
dissociation constant, pKa of the drug
lipid solubility, K o/w
pH at absorption site.
Most drugs are either weak acids or weak bases whose degree
of ionization is depend upon pH of biological fluid.
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 8866
87. For a drug to be absorbed, it should be unionized and the
unionized portion should be lipid soluble.
The fraction of drug remaining unionized is a function of both
Dissociation constant (pKa) and pH of solution.
The pH partition theory is based on following assumption:
GIT acts as a lipoidal barrier to the transport of the drug
The rate of absorption of drug is directly proportional to its
fraction of unionised drug
Higher the lipophilicity of the unionised degree, better the
absorption.
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 8877
88. HENDERSON HASSELBATCH EQUATION
For acid,
pKa - pH = log[ Cu/Ci ]
For base,
pKa – pH = log[ Ci/Cu ]
Eg. Weak acid aspirin (pKa=3.5) in stomach (pH=1) will
have > 99%of unionized form so gets absorbed in stomach
Weak base quinine (pKa=8.5) will have very negligible
unionization in gastric pH so negligible absorption
Several prodrugs have been developed which are lipid
soluble to overcome poor oral absorption of their parent
compounds.
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 8888
89. eg. Pivampicilin, the pivaloyloxy-methyl ester of ampicilin
is
More lipid soluble than ampicilin.
Lipid solubility is provided to a drug by its partition
coefficient between
An organic solvent and water or an aq. Buffer (same pH of
ab. Site)
E.g. Barbital has a p.c. of 0.7 its absorption is 12%
Phenobarbital ( p.c = 4.8 absorption=12%)
Secobarbital (p.c =50.7 absorption=40%)
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 8899
90. 2)DRUG SOLUBILITY
The absorption of drug requires that molecule be in solution at absorption site.
Dissolution, an important step, depends upon solubility of drug substance.
pH solubility profile:
pH environment of GIT varies from Acidic in stomach to slightly Alkaline in a
small intestine.
soluble
1)Basic drug 1) Acidic medium( stomach)
2)Acidic drug 2) basic medium( intestestine)
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 9900
91. Improvement of solubility:
Addition of acidic or basic excipient
Ex: Solubility of Aspirin (weak acid) increased by addition
of basic excipient.
For formulation of CRD , buffering agents may be added to
slow or modify the release rate of a fast dissolving drug.
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 9911
92. PHARMACEUTICAL FACTORS
MEANS Absorption rate depends on the dosage
Form which is administred,ingredients used, procedures
Used in formulation of dosage forms.
The availability of the drug for absorption from the
dosage forms is in order.
Solutions > Suspensions > capsules > Compressed
Tablets > Coated tablets.
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 9922
93. SOLUTIONS
Shows maximum bioavailability and factors affecting
Absorption from solution are as follows
1.Chemical stability of drug
2.Complexation: between drug and exipients of formulation
to increase the solubility, stability.
3. Solubilization: incorporation of drug into micelles to
increase the solubility of drugs.
4. Viscosity
5. Type of solution: Whether aqueous or oily solution.
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 9933
94. SUSPENSIONS:
It comes next after solutions with respect to bioavailability
Factors that affects absorption from suspensions are
1.Particle size and effective surface area of dispersed phase
2. Crystal form of drug: some drug can change their crystal
structure.
Eg. Sulfathiazole can change its polymorphic form, it can be
overcome by addition by adding PVP.
3. Complexation: Formation of nonabsorbable complex between
drug and other ingredients.
Eg. Promazine forms a complex with attapulgite.
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 9944
95. 4. Inclusion of surfactant
Eg. The absorption of phenacitin from suspension is increased in
presence of tween 80.
5. Viscosity of suspension
Eg. Methyl cellulose reduces the rate and absorption of
nitrofurantoin
6. Inclusion of colourants:
Eg. Brilliant blue in phenobarbitone suspension.
0088//1100//22001100 KKLLEECCOOPP, NNiippaannii 9955
96. CAPSULES
Two types of capsule
1.Hard gelatin capsule
2. Soft gelatin capsule
0088//1100//22001100 KKLLEECCOOPP, NNiippaannii 9966
97. HARD GELATIN CAPSULE
The rate of absorption of drugs from capsule is function
Of some factors.
1.Dissolution rate of gelatin shell.
2.The rate of penetration of GI fluids into encapsulated mass
3.The rate at which the mass disaggregates in the GI fluid
4. The rate of dissolution.
5. Effect of excipients;
a).Diluents
b).Lubricants
c). Wetting characteristics of drug
d).Packing density
0088//1100//22001100 KKLLEECCOOPP, NNiippaannii 9977
98. SOFT GELATIN CAPSULE
SGS has a gelatin shell thicker than HGS,but shell is
Plasticized by adding glycerin,sorbitol.SGS may used
To contain non aqueous solution or liquid or semi solid.
SGC have a better bioavailability than powder filled HGC
And are equivalent to emulsions.
Eg. Quinine derivative was better absorbed from SGC
Containing drug base compared with HGC containing
HCl salts.
Grieseoflavin exhibited 88% absorption from soft gelatin
Capsules compared to HGC(30%)
0088//1100//22001100 KKLLEECCOOPP, NNiippaannii 9988
100. Compressed tablets
Bioavailability are more due to large reduction
in surface area.
A B
Intact tablets a granules primary drug particles
K2
K3
Drug in GI fluid
K1
K4
Drug absorbed in body
0088//1100//22001100 KKLLEECCOOPP, NNiippaannii 110000
101. The rate constants decrease in the following order.
K3>>K2>>K1
The overall dissolution rate and bioavailability of a poor
Soluble drugs is influenced by
1.The physicochemical properties of liberated particles.
2. The nature and quantity of additives.
3. The compaction pressure and speed of compression.
4. The storage and age of tablet
0088//1100//22001100 KKLLEECCOOPP, NNiippaannii 110011
102. 1.Effect of diluents :
Na Salicylates + starch = Faster dissolution
Na salicylates + lactose=Poor dissolution.
2.Effect of Granulating agent:
Phenobarbital + Gelatin solution=Faster dissolution
Phenobarbital+PEG 6000= poor dissolution.
3.Effect of lubricants:
Magnesium stearate will retard the dissolution of aspirin tablet
Whereas SLS enhance the dissolution.
0088//1100//22001100 KKLLEECCOOPP, NNiippaannii 110022
103. 4.Effect of disintegrants:
Starch tend to swell with wetting and break apart the dosage
form. It is reported that 325mg of salicylic acid tablet were
prepared by using different concentrations (5%,10%,20%) and
max. dissolution was achieved With 20% starch.
5. Effect of colorants:
6.Effect of Compression force:
0088//1100//22001100 KKLLEECCOOPP, NNiippaannii 110033
104. COATED TABLETS:
There are three types of coating
Sugar coating
Film coating
Enteric coating
SUGAR COATING:
Sugar,Shellac,fatty glycerides, bees wax, silicone resin
Sub coating agent: Talc,acacia,starch.
FILM COATING:
Polymers, dispersible cellulose derivatives like HPMC
CMC.
ENTERIC COATING:
Shellac, cellulose acetate phthalate etc.
0088//1100//22001100 KKLLEECCOOPP, NNiippaannii 110044
105. Factors affecting the drug release are
1.Thickness of coating
e.g.. Quinine shows decrease in rate of absorption
if coated with cellulose acetate phthalate.
2.The amount of dusting powder:
3.Effect of ageing:
e.g. The shellac coated tablets of Para amino salicylic
acid when given after two years plasma concentration
of 6-7mg/100ml. However the tablets stored for 3½ years
showed plasma concentration of only 2mg/100ml which is
the sub therapeutic effect.
0088//1100//22001100 KKLLEECCOOPP, NNiippaannii 110055
114. INTRAVENOUS ROUTE:
Absorption phase is bypassed
(100% bioavailability)
1.Precise, accurate and almost immediate onset
of action,
2. Large quantities can be given, fairly pain free
3. Greater risk of adverse effects
a. High concentration attained rapidly
b. Risk of embolism
0088//1100//22001100 KKLLEECCOOPP, NNiippaannii 111144
118. Factors determining rate of drug absorption:
1. Vascularity to the inj. Site:
Blood flow rates to intramuscular tissues are:
Arm (deltoid) > thigh (vastus lateralis) > buttocks
(gluteus maximus).
2. Lipid solubility and ionisation of drug.
3. Molecular size of drug.
4. Volume of inj. And drug concentration.
5. pH & viscosity of inj. vehicle.
0088//1100//22001100 KKLLEECCOOPP, NNiippaannii 111188
119. SUBCUTANOUS ROUTE:
1. Slow and constant absorption
2. Absorption is limited by blood flow, affected if
circulatory problems exist.
3. The blood supply to this is poorer than that of muscular
tissue.
4. Concurrent administration of vasoconstrictor will slow
absorption, e.g. Epinephrine.
5. The absorption is hastened by massage, application of
heat to increase blood flow and inclusion of enzyme
Hyaluronidase in drug solution.
00 88e//11g00//.22 00I1100nsulin. KKLLEECCOOPP, NNiippaannii 111199
121. TOPICAL ADMINISTRATION:
• MUCOSAL MEMBRANES(eye drops, antiseptic,
sunscreen, nasal, etc.)
•SKIN
a. Dermal - rubbing in of oil or ointment
(local action)
b. Transdermal - absorption of drug through
skin (systemic action)
i. stable blood levels
ii. no first pass metabolism
iii. drug must be potent.
0088//1100//22001100 KKLLEECCOOPP, NNiippaannii 112211
123. The stratum corneum is the outermost layer of the epidermis
and is composed mainly of dead keratinized cells (from lack of
oxygen and nutrients). It has a thickness between 10 - 40 μm.
The dermis is the layer of skin beneath the epidermis. It
contains the hair follicles, sweat glands, sebaceous glands,
apocrine glands, lymphatic vessels and blood vessels.
Hypodermis - Its purpose is to attach the skin to underlying
bone and muscle as well as supplying it with blood vessels and
nerves. The main cell types are fibroblasts, macrophages and
adiposities (the hypodermis contains 50% of body fat).
0088//1100//22001100 KKLLEECCOOPP, NNiippaannii 112233
125. OCULAR ADMINISTRATION
Eye is the most easily accessible site for topical
administration of a medication.
Topical application of drug to eyes meant for :
Mydriasis, miosis, anaesthesia, treatment of
infection, glaucoma etc.
Opthalmic solution are administered into cul-de-sac.
Barrier to intra occular penetration is cornea. It
possess both hydrophilic and lipophilic characterstics.
pH of lacrimal fluid is 7.4.
pH of lacrimal fluid influences absorption of weak
electrolyte like Pilocarpine.
0088//1100//22001100 KKLLEECCOOPP, NNiippaannii 112255
126. OCULAR ADMINISTRATION
High pH of formulation: decrease tear flow and
Low pH of formulation: increases tear flow.
Human eye can hold around 10 microlitre of fluid.
So small volume in concentrated form increases
effectiveness.
Viscosity empartners increases bioavailability eg,
oily solutions, ointment etc.
Systemic entry of drug occur by lacrimal duct which
drains lacrimal fluid into nasal cavity.
0088//1100//22001100 KKLLEECCOOPP, NNiippaannii 112266
127. Composition of eye
Water - 98%
Solid -1.8%
Organic element –
Protein - 0.67%, sugar - 0.65%, Nacl - 0.66%
Other mineral element sodium, potassium and
ammonia - 0.79%
0088//1100//22001100 KKLLEECCOOPP, NNiippaannii 112277
129. Characteristics required to
optimize ocular drug delivery system
Good corneal penetration.
Prolong contact time with corneal tissue.
Simplicity of instillation for the patient.
Non irritative and comfortable form (viscous solution
should not provoke lachrymal secretion and reflex
blinking)
Appropriate rheological properties concentrations of
the viscous system.
0088//1100//22001100 KKLLEECCOOPP, NNiippaannii 112299
130. Advantages
Increase ocular residence….. Improving
bioavailability
Prolonged drug release….. better efficacy
Less visual & systemic side effects
Increased shelf life
Exclusion of preservatives
Reduction of systemic side effects
Reduction of the number of administration
Better patient compliance
Accurate dose in the eye…. a better therapy
0088//1100//22001100 KKLLEECCOOPP, NNiippaannii 113300
133. INHALATIONAL ROUTE:
1.Gaseous and volatile agents and aerosols.
2.Rapid onset of action due to rapid access to circulation
a.Large surface area
b.Thin membranes separates alveoli from
circulation
c.High blood flow
Particles larger than 20 micron and the particles impact in
the mouth and throat. Smaller than 0.5 micron and they
aren't retained.
0088//1100//22001100 KKLLEECCOOPP, NNiippaannii 113333
137. Advantages
Rapid drug absorption via highly-vascularized
mucosa
Rapid onset of action
Ease of administration, non-invasive
Avoidance of the gastrointestinal tract and first-pass
metabolism
Improved bioavailability
Lower dose/reduced side effects
Improved convenience and compliance
Self-administration.
0088//1100//22001100 KKLLEECCOOPP, NNiippaannii 113377
138. Disadvantages
Nasal cavity provides smaller absorption surface area
when compared to GIT.
Relatively inconvenient to patients when compared to
oral delivery since there is possibility of nasal
irritation.
The histological toxicity of absorption enhancers
used in the nasal drug delivery system is not yet
clearly established.
0088//1100//22001100 KKLLEECCOOPP, NNiippaannii 113388
139. Enhancement in absorption
Following approaches used for absorption
enhancement :-
Use of absorption enhancers
Increase in residence time.
Administration of drug in the form of microspheres.
Use of physiological modifying agents
0088//1100//22001100 KKLLEECCOOPP, NNiippaannii 113399
140. Enhancement in absorption
Use of absorption enhancers:-
Absorption enhancers work by increasing the rate
at which the drug pass through the nasal mucosa.
Various enhancers used are surfactants, bile salts,
chelaters, fatty acid salts, phospholipids,
cyclodextrins, glycols etc.
0088//1100//22001100 KKLLEECCOOPP, NNiippaannii 114400
141. Various mechanisms involved in absorption
enhancements are:-
Increased drug solubility
Decreased mucosal viscosity
Decrease enzymatic degradation
Increased Paracellular transport
Increased transcellular transport
0088//1100//22001100 KKLLEECCOOPP, NNiippaannii 114411
142. Various mechanisms involved in
absorption enhancements are:-
Increase in residence time:-
By increasing the residence time the increase in
the higher local drug concentration in the mucous
lining of the nasal mucosa is obtained.
Various mucoadhesive polymers like
methylcellulose, carboxy methyl cellulose or
polyarcylic acid are used for increasing the residence
time.
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 114422
143. Various mechanisms involved in
absorption enhancements are:-
Use of physiological modifying agents:-
These agents are vasoactive agents and exert their
action by increasing the nasal blood flow.
The example of such agents are histamine,
leukotrienene D4, prostaglandin E1 and β-adrenergic
agents like isoprenaline and terbutaline.
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 114433
144. Applications of nasal drug delivery
A. Nasal delivery of organic based pharmaceuticals :-
Various organic based pharmaceuticals have been
investigated for nasal delivery which includes drug
with extensive presystemic metabolism.
E.g. Progesterone, Estradiol, Nitroglycerin,
Propranolol, etc.
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 114444
145. Applications of nasal drug delivery
B. Nasal delivery of peptide based drugs :-
Nasal delivery of peptides and proteins is depend
on –
The structure and size of the molecule.
Nasal residence time
Formulation variables (pH, viscosity)
E.g. calcitonin, secretin, albumins, insulin,
glucagon, etc.
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 114455
149. Advantages
Smaller doses can be administered locally.
Reduce the potential incidence of adverse systemic
effect.
It used when a drug is poorly absorbed orally, e.g. Na
cromoglicate.
It is used when drug is rapidly metabolized orally,
e.g. isoprenaline
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 114499
152. EEvveerrtteedd ssmmaallll iinntteessttiinnee ssaacc
tteecchhnniiqquuee
Isolation of rat intestine
Inverting the intestine
Filling the sac with drug free
buffer solution
Immersion of sac in Erlenmeyer
flask containing drug buffer
solution
Contd… 0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 115522
153. Flask & its contents
oxygenated & agitated at
37oC for specific period of
time
After incubation, the serosal
content is assayed for drug
content
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 115533
154. Figure( reverted ssaacc tteecchhnniiqquuee))
Serosal side
Mucosal side
(intestinal segment before eversion)
Serosal side
Buffer solution
Ligature
Mucosal side
0088//1100//22001100 (after eveKKrLLsEEiCoCOOnPP),, NNiippaannii 115544
157. cannula
Plain buffer
Buffer solution
with drug
Water
maintained at
37o C
a00e88r//11a00t//22o00r1100 KKLLEECCOOPP,, NNiippaannii 115577
(FIG: EVERTED SAC MODIFICATION)
158. PPrroocceedduurree
Animal fasted for 20-24hrs
Water is allowed ad libitum
Animal killed with blow on
head or anesthetized with
ether or chloroform
Entire small intestine is
everted
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 115588
Contd…
.
159. Segments of 5-15cm length are cut
from specific region of the intestine
Distal ends tied & proximal end is
attached to cannula
Segments suspended in 40-100ml of
drug mucosal solution.
About 1ml/5cm length of drug free
buffer is then placed in serosal
compartment
Mucosal solution aerated
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 115599
165. Everted iinntteessttiinnaall rriinngg oorr
sslliiccee tteecchhnniiqquuee
The entire small intestine(everted) is
isolated from fasted expt animal
Intestine cut wit scalpel or scissors
into ring like slices, 0.1-0.5cm length
Intestine washed with buffer & dried
by blotting with filter paper
Dried rings transferred to stoppered
flask containing buffer with drug at
37oC
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii Contd… 116655
166. Contents are continuously
agitated & aerated.
At selected time intervals, the
tissues slices are assayed for drug
content
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167. AAddvvaannttaaggeess
SSiimmppllee && rreepprroodduucciibbllee..
KKiinneettiicc ssttuuddiieess ccaann bbee ppeerrffoorrmmeedd..
Process of cutting the intestine into rings may expose
highly permeable areas of cut or damage tissue to
medium.
MAJOR DISADVANTAGE OF IN-VITRO METHODS
is that the are based on approximation &
oversimplification of the actual in-vivo conditions.
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 116677
170. AABBSSOORRPPTTIIOONN FFRROOMM
SSMMAALLLL IINNTTEESSTTIINNEE
Adult male rats fasted for
about 16-24hrs.
Animal anesthetized, a
midline abdominal incision
is made.
isolation & cannulation of
Small intestine
Contd… 0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 117700
171. Replacement of intestine.
Incision closed & duodenal
cannula is attached to an infusion
pump
Intestine cleared off particulate
matter using drug free buffer
(1.5ml/30min)
Drug buffer solution is perfused
(1.5ml/30min)
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii Contd… 117711
172. Samples at 10min interval
collected from ileal cannula
Samples assayed for drug
content
Relative rate of absorption
calculated
Relative rate of absorption = difference in the drug
concentration entering & leaving the intestine
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 117722
174. Here, single or multiple intestinal loops are used for studying
absorption
Adult male rat fasted & water with held for
1-2hrs before expt.
Under anesthesia an abdominal incision is
made & small intestine exposed.
Placement of proximal ligature & distal
ligature.
Introduction of drug solution.
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 117744
Contd..
175. Replacement of intestinal loop.
After a predetermined period of time,
animal is sacrificed.
Intestinal loop is rapidly excised &
homogenized.
The amount of drug unabsorbed is
determined.
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 117755
176. For preparing multiple loops, the procedure is identical to
single loop preparation with a distance of approximately
one half inch left between successive loops.
AAddvvaannttaaggeess
SSiimmppllee && rreepprroodduucciibbllee..
Only 1 sample can be obtained from the
experimental animal.
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 117766
177. Absorption ffrroomm tthhee ssttoommaacchh
Fasted adult male rats anesthetized, stomach
exposed & cardiac end ligated.
Introduction of cannula (pylorus).
Lumen washed several times with saline &
subsequently with 0.1N HCl containing 0.15M NaCl
Drug solution of known concentration is
introduced into the stomach
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 117777
Contd….
178. After 1hr, the drug solution is removed from
the gastric pouch & assayed for drug content.
% of drug absorbed in 1hr may be
calculated.
The gastric pouch may also be homogenized
& analyzed for drug.
In-situ techniques equate absorption with loss of drug from the GI
lumen & if a drug is significantly accumulated or metabolized in gut
wall, one will get an overestimate of the amount of drug absorbed
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 117788
182. PPrroocceedduurree
A blank urine or blood sample is taken for the
test animal before the experiment.
Administration of test dosage form.
Blood or urine sampling.
Assay for drug content & determination of rate
& extent of drug absorption.
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 118822
184. Log dose
Fka/2.303
Duration of response time
x
y
Where,
F= bioavailability.
Ka= the absorption rate constant.
d= threshold dose
d
0088//1100//22001100 KKLLEECCOOPP,, NNiippaannii 118844