Bioadhesive drug delivery system

BIOADHESION
PRESENTED BY
SUNIL BOREDDYSUNIL BOREDDY
M.Pharmacy (Pharmaceutics)M.Pharmacy (Pharmaceutics)

CONTENTSCONTENTS
2
What is a Bioadhesive Polymer?
Bioadhesion and Drug Absorption
Bioadhesive Drug Delivery Systems
Types of Bioadhesive Formulations
Targets for Bioadhesive Formulations
Summary

What is a bioadhesive polymer?What is a bioadhesive polymer?
3
Definition
History
Examples

Definition of a Bioadhesive PolymerDefinition of a Bioadhesive Polymer
4
A polymer is a substance formed by the linkage of a large
number of small molecules known as monomers. A
bioadhesive polymer is a synthetic or natural polymer which
binds to biological substrates such as mucosal membranes.
Such polymers are sometimes referred to as biological ‘glues’
because they are incorporated into drugs to enable the drugs
to bind to their target tissues.

Mucosal membranesMucosal membranes
5
These are moist membranes that line passageways and
structures in the body that lead to the outside environment
such as the mouth, respiratory tract, gastrointestinal tract,
nose and vagina. They secrete a viscous fluid known as
mucus, which acts as a protective barrier and also lubricates
the mucosal membrane. The primary constituent of mucus is
a glycoprotein known as mucin as well as water and inorganic
salts.

HistoryHistory
6
Bioadhesive drug delivery formulations were introduced in 1947
when gum tragacanth was mixed with dental adhesive powder.
The aim was to deliver Penicillin into the oral mucosa. This later
became Orabase®, a formulation used to treat mouth ulcers. This
product is available as a paste which will stick to the wet surfaces
of the mouth and form a protective film over the mouth ulcer.
Orabase paste contains polymers such as gelatin, pectin and
carboxymethylcellulose.
Some examples of Orabase products are shown belowSome examples of Orabase products are shown below

Examples of polymersExamples of polymers
7
Bioadhesive polymers come from both natural and synthetic sources,
some common examples are highlighted below:
 Acacia gumAcacia gum This natural polymer is a dried gum obtained from the stem and
branches of the tree Acacia senegal. It is used as a thickener in pharmaceuticals.
 Alginic acidAlginic acid Is a natural polymer found in the cell walls of brown algae. It is
widely used in the manufacture of alginate salts such as sodium alginate which
is a constituent of Gaviscon liquid®.
 CarbomersCarbomers Are polyacrylic acid polymers widely used in the pharmaceutical
and cosmetic industries as thickening agents.. Carbomers have a huge
advantage in formulation science because they adhere strongly to mucosal
membranes without causing irritation, they exhibit low toxicity profiles and
are compatible with many drugs.

More examples
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 Hydroxypropyl methylcellulose (HPMC)Hydroxypropyl methylcellulose (HPMC) –– This polymer is included in
preparations used to moisten contact lenses and in oral gels.
 Sodium hyaluronateSodium hyaluronate -- A high molecular weight biological polymer made
of repeating disaccharide units of glucuronic acid and N-acetyl-D -
glucosamine. This polymer is used during intraocular surgery to protect
the cornea and also acts as a tear substitute in the treatment of dry eyes.
Other examples of polymers include:
-- pectinpectin
-- polyvinylalcohol (PVA)polyvinylalcohol (PVA)
- polyvinylpyrrolidone (PVP)polyvinylpyrrolidone (PVP)
-- tragacanthtragacanth

Bio adhesion and Drug AbsorptionBio adhesion and Drug Absorption
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Drug absorption is the process by which a drug leaves its site of administration and
enters the general circulation. A drug has to cross several cell membranes before
reaching its target tissue or organ.
These membranes act as barriers which control the transport of drugs and other
molecules across cells. The general structure of a cell/plasma membrane consists
of a matrix of proteins surrounded by a phospholipid bilayer.
Drugs may cross a cell membrane by passive diffusion, facilitated passive diffusion,
active transport or pinocytosis. Drug absorption is determined by physicochemical
properties of drugs, their formulations (e.g. tablet,capsule,solution) and routes of
administration such as oral, parenteral or rectal.

Passive Diffusion
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Diffusion is the tendency of molecules to spread into an available space. In the
process of passive diffusion the transport of molecules across cell membranes
depends very much on the concentration of the molecule.
Most drug molecules are transported across membranes by diffusion from a region
of high concentration (eg.Gastrointestinal fluids) to one of a lower concentration
such as blood.
Since cell membranes are lipid in nature, lipid
soluble drugs are able to diffuse across the
membrane more rapidly than non-lipid soluble
drugs. Small molecules are also able
to penetrate the membrane more rapidly than
larger ones.

Facilitated passive diffusion
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This is when molecules are transported across membranes and into cells with the
help of carrier proteins. These proteins only interact with certain molecules and
therefore exhibit specificity.
The process of carrier-mediated transport depends on the availability of carriers,
this means that at a particular point during transport the carrier will become
saturated.
An example of this type of diffusion is the
transport of glucose from blood.

Active TransportActive Transport
Active transport is the movement
of molecules and ions against
their concentration gradients,
from lower to higher
concentrations. This form of
transport requires an input of
energy from cells which is
obtained from ATP (Adenosine
Triphosphate).
12

Pinocytosis
13
Pinocytosis (a form of endocytosis)
allows a cell to engulf large
molecules and fluid that may be
present in the extracellular region.
The cell membrane folds inwards,
encloses the fluid or particle to be
transported and then fuses to form a
vesicle.
The vesicle detaches from the
membrane and moves to the
interior of the cell. Pinocytosis
plays a role in the transport of
protein drugs.

Bioadhesion and Drug AbsorptionBioadhesion and Drug Absorption
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The adhesion of bioadhesive drugs to mucosal membranes leads to an
increase in the concentration of the drug at its site of action. This means
that a greater amount of drug is available at the specific target site to
cause the desired therapeutic effect.
The concept of using bioadhesive polymers in drug delivery systems is
therefore quite important because it enhances the absorption of drugs.

Bioadhesive Drug DeliveryBioadhesive Drug Delivery
SystemsSystems
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In bioadhesive drug delivery systems, the term bioadhesionbioadhesion is used to describe the
bonding or adhesion between a synthetic or natural polymer and soft tissues such
as epithelial cells. The term mucoadhesionmucoadhesion is used to describe adhesion interactions
between polymers and mucus or mucosal surfaces.
Mechanisms of bioadhesionMechanisms of bioadhesion
The mechanisms responsible in the formation of bioadhesive bonds are not fully
known, however most research has described bioadhesive bond formation as a
three step process.
Step 1 : Wetting and swelling of polymer
Step 2 : Interpenetration between the polymer chains and the mucosal membrane
Step 3 : Formation of chemical bonds between the entangled chains

Bioadhesive Drug Delivery SystemsBioadhesive Drug Delivery Systems
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Step 1Step 1
The wetting and swelling step occurs when the polymer spreads over the surface
of
the biological substrate or mucosal membrane in order to develop an intimate
contact with the substrate. This can be readily achieved for example by placing a
bioadhesive formulation such as a tablet or paste within the oral cavity or vagina.
Bioadhesives are able to adhere to or bond with biological tissues by the help of
the
surface tension and forces that exist at the site of adsorption or contact. Swelling
of
polymers occur because the components within the polymers have an affinity for
water.
The image below shows swelling of a polymerThe image below shows swelling of a polymer

Bioadhesive Drug Delivery SystemsBioadhesive Drug Delivery Systems
17
Step 2Step 2
The surface of mucosal membranes are composed of high molecular weight
polymers known as glycoproteins. In step 2 of the bioadhesive bond formation, the
bioadhesive polymer chains and the mucosal polymer chains intermingle and
entangle to form semi permeable adhesive bonds. The strength of these bonds
depends on the degree of penetration between the two polymer groups. In order to
form strong adhesive bonds, one polymer group must be soluble in the other and
both polymer types must be of similar chemical structure.
The interpenetration of polymer chainsThe interpenetration of polymer chains
Bioadhesive
polymer chains
Mucus
polymer chains

Bioadhesive Drug delivery SystemsBioadhesive Drug delivery Systems
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Step 3Step 3
This step involves the formation of weak chemical bonds between the entangled
polymer chains. The types of bonding formed between the chains include primary
bonds such as covalent bonds and weaker secondary interactions such as van der
Waals Interactions and hydrogen bonds. Both primary and secondary bonds are
exploited in the manufacture of bioadhesive formulations in which strong adhesions
between polymers are formed.
MechanismsMechanisms of bioadhesionof bioadhesion
Step 3Step 3
► ◄

Characteristics of Bioadhesive
polymers
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In order for polymers to adhere to mucosal surfaces or epithelial cell they must
ideally possess certain characteristics:
 FlexibilityFlexibility-- The flexibility of bioadhesive polymers is important because it controls the
extent of the interpenetration between the polymers and mucosal/epithelial surfaces.
 HydrophilicityHydrophilicity – Polymers that are hydrophilic in nature are able to form strong
adhesive bonds with mucosal membranes because the mucus layer contains large
amounts of water.
 Hydrogen bondingHydrogen bonding –– Hydrogen bonding between the entangled polymer chains
forms strong adhesive bonds, therefore the presence of hydrogen bond – forming groups
such as OH and COOH groups are vital in large quantities.
 High molecular weightHigh molecular weight –– Polymers with a high molecular weight are desirable
because they provide more available bonding sites.
 Surface tensionsSurface tensions –– Surface tensions are needed to spread the bioadhesive polymer into
the mucosal layer epithelial surface.

Types of Bioadhesive Formulations
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1.Solid Bioadhesive Formulations1.Solid Bioadhesive Formulations: Examples of such formulations are given
below.
Tablets :Tablets : Dry formulations such as tablets are able to form strong interactions with
mucosal surfaces by attracting water from the mucosal surface. An example is
Buccastem® which is used in the treatment of nausea, vomiting and vertigovertigo. It is
administered to the buccal mucosa (inside of the cheeks).
Inserts:Inserts: These include ocular inserts such as eye drops and eye gels. An example is
Pilogel® which is used in the treatment of glaucoma (raised pressure in the eye).
Pilogel® contains the bioadhesive agent carbomer 940,which minimises irritation
and prevents the loss of product by keeping the gel in place.
Lozenges:Lozenges: Bioadhesive lozenges containing antibiotics and local anaesthetics can
be used topically to treat conditions affecting the mouth. Research has shown
that bioadhesive lozenges are able to release drugs in a controlled manner by
prolonging the drug release.

Types of Bioadhesive FormulationsTypes of Bioadhesive Formulations
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2. Semi-solid bioadhesive Formulations2. Semi-solid bioadhesive Formulations
Gels :Gels :Bioadhesive polymers that are able to form gels include polyacrylic acidpolyacrylic acid which
adheres to mucosal surfaces in a cross-linked form. Gel formulations are used to
target several parts of the body including the eye, vagina and oral cavity. An
advantage of gels is that they are able to form a very close contact with mucosal
membranes and rapidly release drugs at their site of absorption.
Films:Films: Bioadhesive films that are flexible in nature can be used to directly deliver
drugs to specific mucosal membranes. They form a very close contact with
the membrane and are able to deliver an accurate dose of drug to the site of
absorption. An example of a bioadhesive film is Zilactin® which is used in the
treatment of cold sores and mouth ulcers.

Types of Bioadhesive Formulations
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3.Liquid Bioadhesive Formulations3.Liquid Bioadhesive Formulations
Viscous liquids:Viscous liquids: Viscous liquids containing bioadhesive polymers such as
carboxymethyl cellulose may be used to protect mucosal membranes from damage
and irritation. They can also be used to deliver drugs to specific sites. An example is
artificial tears, a carbomer solution used to treat dry eyes.
Gel-forming liquids:Gel-forming liquids: These formulations are administered as liquids but undergo a
change in their form in response to conditions such as temperature and pH. Such
formulations are used for the controlled-release of drugs into the eye.

Targets for Bioadhesive FormulationsTargets for Bioadhesive Formulations
Bioadhesive or mucoadhesive
formulations have been targeted to
various anatomical locations to aid drug
delivery and absorption. These
structures possess mucous membranes
which protect the cell from damage.
Drug delivery to each anatomical region
is discussed below.
Table 1 : Sites to which bioadhesiveTable 1 : Sites to which bioadhesive
formulations are targetedformulations are targeted
Body siteBody site SystemsSystems
Eye Mucoadhesive eye
drops / inserts
Nasal cavity Nasal drug delivery
systems
Oral cavity Dental gels / buccal
systems
Skin Patches, tapes,
dressings
Vagina Local vaginal
delivery systems
Rectum Local/systemic
rectal delivery
systems
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1.1.The eyeThe eye
The eye is one of the most important and complex organs of the body, because of
its complicated anatomy many things can go wrong with the eye. Topical drug
delivery systems to the eye can be very difficult to achieve because the eye has
several protective mechanisms in place to get rid of foreign substances.
A brief anatomy of the eyeA brief anatomy of the eye
An effective ocular drug delivery system must
be easy to use, comfortable to the patient
and maintain substantial concentrations of
the drug in the eye to produce therapeutic
effects.

Some conditions of the eye
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 Conjunctivitis –Conjunctivitis – this is an inflammation of the conjunctivae, which are mucous
membranes covering the whites of the eye and the inside of the eyelids. It is caused
by bacteria, viruses or allergens and the signs and symptoms displayed by the
patient will be dependent on the type of conjunctivitis. The symptoms include:
redness of the eye, grittiness or itchy eyes and the presence of a sticky or watery
discharge.
 Dry eye –Dry eye – this occurs when people don’t have enough tears or the adequate
composition of tears required to lubricate the eyes. The occurrence of dry eye
increases with age and is therefore common in older people. The eyes become
itchy, gritty, painful and have a burning sensation.
 Glaucoma –Glaucoma – This disorder is characterised by pressure in the eyeballs and causes
excessive amounts of aqueous humouraqueous humour (the fluid that fills the eyeballs). This puts
pressure on the optic nerves and compresses the blood vessels in the eye. The
resultant effects include abnormalities in vision and total blindness.

Ocular Bioadhesive Formulations
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Various ocular bioadhesive formulations have been designed to treat specific
conditions affecting the eye. Such formulations can produce a prolonged or
sustained release of drugs into the eye. Drugs containing polymers attach to the
mucinmucin on the conjunctival surface by means of non-covalent bonding. The polymer
is able to remain in contact with the surface of the eye until mucin replaces itself or
until the pressure of blinking removes the drug from the eye.
EXAMPLES OF PRODUCTSEXAMPLES OF PRODUCTS
 HypotearsHypotears®® and Sno Tears®Sno Tears® Eye drops are used for dry eye and tear deficiency
and they generally lubricate the eyes. They both contain the polymer polyvinyl alcohol
(PVA) which increases tear production and protects the eye from further irritation.
The monomer from which
PVA is made
Vinyl alcohol

Ocular Bioadhesive Formulations
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 GelTearsGelTears® and Viscotears®® and Viscotears® Liquid gel eye drops are used for dry eye
conditions and contain carbomer 980 (polyacrylic acid). Carbomers lubricate
the eye by clinging to the surface of the eye. This can help reduce the
frequency of their application into the eye.
 Pilogel®Pilogel® Is an eye gel used in the treatment of glaucoma. It contains the high
molecular weight polymer polyacrylic acid. The polymer increases the viscosity
of the gel which provides a prolonged retention of the gel in the eye.
POLYACRYLIC ACIDPOLYACRYLIC ACID

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2. The Nasal Cavity2. The Nasal Cavity
The nasal cavity is the air passage behind the nose. This is the source of the
moisture which is added to air during the breathing process. The nasal cavity has a
complex structure and can become inflamed during conditions such as the common
cold, nasal allergies and flu.
Drugs such as antihistamines and steroids are administered as nasal drops or nasal
sprays to treat conditions affecting the nose. However nasal mucociliary clearancemucociliary clearance
affects the retention and therefore the effects of the drugs in the nose.
Mucociliary clearance transports mucus from the cells
lining the nose and protects the respiratory tract from
damage caused by inhaled substances including
dirt particles and medicines.

Nasal Bioadhesive Formulations
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By mixing drugs targeted for the nose with bioadhesive polymers, the process of
mucociliary clearance of the drug can be overcome. The effects of bioadhesive
polymers on mucociliary clearance was examined by Zhou and DonovanZhou and Donovan (1996).
All the polymers examined showed decreases in mucociliary clearance.
Methylcellulose exhibited the most reduction in mucociliary clearance whilst
Carbopol 934P showed the least reduction in mucociliary clearance in the rats used.
 RhinocortRhinocort®® Nasal spray is a powdered mixture of the steroid Beclomethasone
dipropionate(50μg) and 30mg of Hydroxypropyl cellulose(HPC). Patients
suffering from nasal allergy administer one spray twice a day into the nasal
cavity.The powder sticks to and swells on the cells lining the nose and remains
there until approximately six hours after administration.

Nasal Bioadhesive Formulations
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 BeconaseBeconase®® Nasal spray is used to treat nasal inflammation and nasal allergies
associated with hayfever. It contains the active ingredient Beclometasone
dipropionate and the bioadhesive polymers carboxymethyl cellulose andcarboxymethyl cellulose and
microcrystalline cellulose.microcrystalline cellulose.
 Nasacort®Nasacort® Nasal spray is used to treat allergies that result in inflammation of
the nose. The active ingredient in this product is Triamcinolone acetonide as
well as the bioadhesive polymer microcrystalline cellulosemicrocrystalline cellulose. The polymer swells
in the presence of water and is able to spread across the nasal mucosa thus
helping the distribution of the drug over the mucosal surface.

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3. The oral cavity3. The oral cavity
The oral cavity or the mouth comprises of the cheeks, hard and soft palates and the
tongue. It is an entrance of the digestive system and plays many important
functions which include chewing, speaking and tasting. Some of these functions are
impaired by diseases such as ulcers, microbial infections and inflammation.
Some of the common conditions affecting the oral cavity are discussed on the next
slide.

Common conditions affecting the oral cavity
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 Mouth ulcers :Mouth ulcers : A mouth ulcer can be described as a breach or break in the
mucous membrane that lines the inside of the mouth. The majority of patients
suffer from minor aphthous ulcers (MAU). These ulcers are roundish, shallow,
grey-white in colour and are painful. They are small and appear in small crops.
 Oral thrush:Oral thrush: This is an infection caused by the fungus Candida albicansCandida albicans in the oral
cavity. It can also arise due to risk factors such as diabetes, recent antibiotic therapy
and inhaled corticosteroids. Oral thrush presents itself as soft creamy-white
patches which can be wiped off. The lesions are painful and can occur anywhere in
the oral cavity.
 Gingivitis:Gingivitis: Gingivitis means inflammation of the gums. It is caused by the build-
up of plaque (a layer of bacteria) on the teeth. The gums become reddened,
swollen and bleed easily with slight trauma such as brushing the teeth.

Oral Bioadhesive Formulations
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Oral bioadhesive formulations are topical products designed to deliver drugs to the
oral cavity which act by adhering to the oral mucosa and therefore produce localised
effects within the mouth.
CorlanCorlan®® Corlan pellets are used in the treatment of mouth ulcers to reduce the
pain, swelling and inflammation associated with mouth ulcers. The active ingredient
of the pellet is Hydrocortisone succinate. It also contains the bioadhesive polymer
AcaciaAcacia which helps prolong the effect of the drug in the oral cavity. For treatment to
be successful each pellet or lozenge must be allowed to slowly dissolve in the
mouth, close to the ulcer.

Oral Bioadhesive Formulations
34
 BonjelaBonjela®® This gel is used in the treatment of the soreness associated with mouth
ulcers. The gel is applied over the ulcer every three to four hours or when needed.
Bonjela® contains hypromellose 4500 which lubricates the ulcers .
 Daktarin®Daktarin® oral gel contains the antifungal agent Miconazole and is used to treat
oral thrush. It also contains an adhesive agent known as pregelatinised potato starchpregelatinised potato starch
which increases the viscosity of the gel and also enables it to stick to the oral
mucosa. Patients are advised apply the gel in the mouth and keep it there for as long
as possible preferably after food so the gel remains intact for longer.
 Corsodyl®Corsodyl® oral gel contains the active ingredient chlorhexidine gluconate and is
brushed on the teeth to inhibit the formation of plaque and therefore improve oral
hygiene. The gel also contains the bioadhesive polymer Hydroxypropyl cellulose(HPC)Hydroxypropyl cellulose(HPC)
which helps retain the gel inside the oral cavity.11111

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3a.The Buccal Mucosa3a.The Buccal Mucosa
The buccal mucosa refers to the inner lining of the lips and cheeks. The epithelium
of the buccal mucosa is about 40-50 cells thick and the epithelial cells become
flatter as they move from the basal layersbasal layers to the superficial layers.
The buccal mucosa is less permeable compared to other oral drug delivery
systems and is unable to retain dosage forms at the site of absorption. The
use of bioadhesive polymers in buccal drug delivery systems allows a better
retention of a dosage form by spreading it over the absorption site.
Examples of ProductsExamples of Products
 BuccastemBuccastem®® Is a drug used in the treatment of nausea, vomiting and vertigo. It
contains the bioadhesive agents Polyvinylpyrrolidone and Xanthan gum.
 SuscardSuscard®® Is a buccal tablet used in the treatment of angina. It contains the
bioadhesive agent Hydroxypropyl methylcellulose (HPMC).

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3b. The sublingual mucosa3b. The sublingual mucosa
The sublingual mucosa surrounds the sublingual gland which is a mucin-producing
salivary glandsalivary gland located underneath the tongue.
This mucosa is relatively permeable and gives a rapid absorption of many
drugs due to its excellent blood supply. The sublingual route of drug delivery
is convenient, accessible and generally well accepted by patients.
Drugs administered via the sublingual route are formulated as tablets, powders,
solutions or aerosol sprays. This route is appropriate for many drugs as long
as the drug is able to go into solution with saliva in the mouth.
Examples of sublingual products include Glyceryl Trinitrate (GTNGlyceryl Trinitrate (GTN) aerosol spray
and tablet which is administered under the tongue for the prophylacticprophylactic treatment of
angina.

Targets for Bioadhesive Formulations
37
4.The Skin4.The Skin
The skin is the outer covering of the body and consists of different layers. It
performs several functions which include:
 Protecting the body from injury and invasion by pathogens
 Preventing the body from becoming dehydrated
 Regulating body temperature
 Production of Vitamin D Cross section of the skinCross section of the skin

Topical Bioadhesive Formulations
38
The drug delivery systems used in this case are required to adhere to the skin for
the purpose of:
 Collecting body fluids
 Protecting the skin
 Providing local or systemic drug delivery
Adhesion can be described as the formation of a new mechanical bond between
the skin and the adhesive agent. Bioadhesive products targeted to the skin are
formulated into different dosage forms which include liquids, powders and
semi-solids such as ointments and transdermal patches.
Transdermal patches are sustained-release devices that release a specific amount
of drug whilst firmly attached to the skin. They must provide a firm, soft contact with
the skin but also allow the patch to be easily removed with minor effort.

Topical Bioadhesive Formulations
39
Examples of ProductsExamples of Products
 VoltarolVoltarol® Emulgel:® Emulgel: This is a gel which provides a local relief from pain and
inflammation in the tendons, muscles and joints. It contains the bioadhesive
polymer carbomercarbomer which aids the absorption of the active drug by spreading it into
the affected area.
 Feldene®:Feldene®: This gel is used in the treatment of conditions which are characterised
by pain, inflammation and stiffness. The active ingredient in this formulation is
piroxicampiroxicam but the gel also contains two bioadhesive agents to increase its retention
at the absorption site. These agents are Carbopol 980Carbopol 980 and hydroxyethyl cellulose.hydroxyethyl cellulose.
 Evorel®:Evorel®: Is a patch used in hormone replacement therapy (HRT) for oestrogen
deficiency. It consists of an adhesive matrix through which the active drug
(estradiol) is evenly distributed. The adhesive polymers used are guar gumguar gum and
polyacrylic acidpolyacrylic acid which holds the patch firmly on the skin surface.

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5. The Vagina5. The Vagina
The vagina is the lower part of the female reproductive tract. It is a muscular tube
lined with mucous membrane which is covered with a layer of stratified squamousstratified squamous
epitheliumepithelium with an underlying layer of connective tissue (lamina proprialamina propria) .
Histology of the vaginal mucosaHistology of the vaginal mucosa

Common conditions affecting the vagina
41
The epithelium of the vagina contains glycogenglycogen, which is broken down enzymes and
bacteria into acids such as lactic acid. This maintains a low vaginal pH which is
normally between 4 and 5.
Such a pH is desirable because it makes the vagina inhospitable to pathogens.
Decreased levels of glycogen in the vagina leads to an increase in vaginal pH and
makes the vagina more susceptible to infection.
Common vaginal infectionsCommon vaginal infections
 Vaginitis :Vaginitis : Vaginitis means inflammation of the vagina and it creates discharge, odour,
irritation or itching. It has many causes which includes infection with TrichomonasTrichomonas
vaginalis,vaginalis, dietary deficiency or poor hygiene.

Common conditions affecting the vagina
42
 Bacterial vaginosis:Bacterial vaginosis: The causal organism often implicated in C. albicansC. albicans
this infection is Gardnerella vaginalisGardnerella vaginalis, although other bacteria
present in the vagina also contribute to the cause. The infection
arises due to the overgrowth of these bacteria. About 50% of
patients will have a thin white discharge with a strong fishy odour.
 Candidiasis (Thrush):Candidiasis (Thrush): Is a common yeast infection caused
by the organism Candida albicansCandida albicans. The signs and symptoms
of thrush are a white cheesy discharge that itches and irritates
the vagina. T. vaginalisT. vaginalis
 Trichomoniasis:Trichomoniasis: Is a sexually - transmitted infection caused
by the organism Trichomonas vaginalisTrichomonas vaginalis. The symptoms in
women include vaginal itching as well as a frothy, foul-smelling,
greenish-yellow discharge.

Vaginal bioadhesive formulations
43
 The intravaginal route has been used to deliver contraceptives as well as
anti-infective agents such as antifungal drugs to exert a local effect. Agents
targeted for the vaginal route have been formulated into various dosage forms
including creams, gels and vaginal tablets.
 Localised application of vaginal formulations enables the spread of these
formulations over the target area, which allows an effective therapy.
 Bioadhesive polymers are incorporated into vaginal formulations to aid the
adhering of the dosage form to its target site. Polymers also increase the retention
of the active drug in the vagina and also optimises the spread of the formulation
over the vaginal epithelium.

Vaginal bioadhesive formulations
Table 2: Examples of vaginal products
ProductProduct Function of ProductFunction of Product Bioadhesive AgentBioadhesive Agent DosageDosage
FormForm
Aci-Jel® Maintains vaginal
acidity
Acacia, Tragacanth Vaginal Gel
Crinone® Used for
Progesterone
deficiency
Carbomer Vaginal Gel
Estring® Restores Oestrogen
deficiency
Silicone Polymers Vaginal
Ring
Gynol-II® Spermicidal
Contraceptive
Carboxymethyl
cellulose
Vaginal
Gel
Zidoval® Treatment of
bacterial
vaginosis
Carbomer Vaginal
Gel
44

Targets for Bioadhesive Formulations
45
6.The Rectum6.The Rectum
The rectum is the terminal or end portion of the
gastrointestinal tract. It is an important route
of administration for drugs that have severe
gastrointestinal side effects. This route is also
suitable for patients who cannot take medicines
via the oral route such as unconscious patients
and infants.
The drugs absorbed from the rectum can escape
breakdown by hepatic enzymes. For this reason
mucoadhesive suppositories have been developed
for the local treatment of diseases such as haemorrhoids
and rectal cancer.

Rectal Bioadhesive Formulations
46
Bioadhesive polymers are incorporated into rectal suppositories to prolong the
retention of the active drug in the rectum. Prolonged retention in the rectum
increases the chances of reaching a therapeutic outcome.
 AnacalAnacal®® Is a rectal ointment used to relieve the symptoms associated with
haemorrhoids. It contains the bioadhesive agent polyethylene high polymer 1500.polyethylene high polymer 1500.
 Germoloids®Germoloids® Is a rectal ointment used to relief the pain, swelling, itchiness and
irritation associated with haemorrhoids. It contains the polymer propylene glycolpropylene glycol.
 Preparation H®Preparation H® Suppositories help shrink the haemorrhoidal tissue which is
swollen by irritation. It contains the polymer polyethylene glycolpolyethylene glycol.

Summary
47
The concept of bioadhesion involves the binding of a natural or synthetic
bioadhesive polymer to biological substrates such as mucous membranes.
Bioadhesive drug delivery systems have been available since the late 1940s
and have become an important route of delivering drugs.
The earlier applications of bioadhesive formulations mainly involved the oral
cavity and the gastrointestinal tract. These days bioadhesive drug delivery
systems have been developed to target a wider variety of mucosal and epithelial
surfaces, these include the vagina, the skin and the nasal cavity.
In most instances bioadhesive formulations are preferred over the conventional
methods of drug delivery. This is because bioadhesion allows the retention of the
active drug over the mucosal surface and prolongs the contact time between the
polymer and mucosal surface.

Bioadhesive drug delivery system

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Bioadhesive drug delivery system