SURFACTANTS AND THEIR PHARMACEUTICAL APPLICATIONS
SURFACTANTS AND THEIR PHARMACEUTICAL
APPLICATIONS
Surfactants:
“Surfactants are
surface active agents/wetting agents that reduce the surface tension of liquids
or that between a liquid and a solid”.
Typically they are organic compounds having a hydrophilic
head and a hydrophobic tail.
These are called surface active because
they interact with the surface of liquid to change its properties (a
lipoprotein in the lung that reduces surface tension and permits more efficient
gas transport).
Surface Tension:
Surface tension is a
property of the surface of a liquid that allows it to resist an external
force, due to the cohesive nature of its molecules.In the liquid state,
molecules are surrounded by other molecules in all direction so net effect is
zero ,but the molecules at surface can only have attractive cohesive forces with
the molecules that are situated adjacent and below it. The net effect is that
the molecule at the surface of the liquid experience an inward force toward the
bulk, such a force pulls the molecules of the surface together, contract the
surface, the tension thus created on a surface by this inward pull is called
surface tension.Units of surface and interfacial tension are mN m–1.
Interfacial Tension:
It is the force per unit area existing at the interfaces between two
immiscible liquid phases.
When two
immiscible liquid are mixed together an interface is formed between these, this
is because the attractive forces between like molecules are stronger then the
attractive forces between molecules of immiscible liquids. Therefore they
remain immiscible.
Structure and properties of a typical surfactant molecule:
Ø
Surfactants are
usually organic compounds
Ø
Surfactants are amphiphilic in
nature i.e.; they contain 2 distinct structural units:
·
Tail or hydrophobic group which has little affinity
for water
·
Head or hydrophilic group which
has strong affinity for water & can be neutral or charged
A Surfactant molecule
Examples of polar
(head)and non polar (tail)groups
|
HEAD
GROUPS
-Hydroxyl group (OH)
-Aldehydic group (CHO)
-Carboxylic group
(COOH)
-Sulfate group
-Nitro group (NO2)
-Amine group (NH2)
-Halogen (CL or Br)
|
TAIL GROUPS
-Lower
alkyl group C3 –C8
(CH3-CH2-CH2---)
-
Branching alkyl chains
-
Aromatic ring such as
benzene
or naphthalene
|
Hydrophilic-Lipophilic Balance (HLB):
Hydrophilic-Lipophilic Balance
(HLB):It is an arbitrary scale from 0 to 20 depicting the
Hydrophilic/Lipophilic balance of a surfactant.
- Products with low HLB are more oil soluble.
- High HLB represents good water solubility.
NOTE: HLB is
numerically calculated number based on surfactants molecular structure, it is
not measured parameter
HLB is a means of expressing the hydrophilic property of
surfactants in figures.
RANGE USE HLB
4-6 W/O emulsifiers
7-9 Wetting agents
8-1
8 O/W emulsifiers
13-1 5 Detergents
15-18 Solubilizing
Properties of surfactants:
Surfactants show the following properties:
a.
Emulsifying
agent:
Lowering of interfacial tension
between oil and water phases facilitates emulsion formation.
b.
Suspending
agent:
The adsorption
of surfactants on insoluble particles enable these particles to be dispersed in
form of a suspension.
c.
Wetting
agents:
Their adsorption
on solid surfaces enable these surfaces to be more readily wetted.
d.
Solubilizer:
The
incorporation of insoluble compounds within micelles of surfactants
can lead to production of clear
solution.
e.
Foaming agent:
A foaming
agent is a surfactant
which when present in small amounts facilitates the formation of foam, or enhances
its colloidal stability by inhibiting the coalescence of bubbles.
f.
Anti-foaming agents:
Surfactants
also act as anti-foaming agents or defoamers.
g. Detergent:
A detergent is a surfactant (or a mixture
containing one or more surfactants) having cleaning properties in dilute
solution (soaps are surfactants and detergents).
Detergents
are also surfactants that reduce the surface tension and aid in wettingthe
surface and the dirt. The solid will be emulsified and foaming generally occurs
and results in washing away of dirt.
Detergents
also form micelles which is the aggregation of molecules ina colloidal
solution.
Drugs as Surfactants:
A wide variety of drugs, including the antihistamines and the tricyclic
depressants, are surface-active because of their amphipathic nature. but the
hydrophobic portion of drug molecule are usually more complex than those of
typical surfactant molecule, being composed of aromatic or heterocyclic ring
system.
Mechanism of action of Surfactants:
When surfactants are dissolved in water they orientate at
the surface so that the hydrophobic regions are removed from the aqueous
environment this is because they replace some of the water molecules in the
surface and the forces of attraction between surfactant and water molecules are
less than those between two water molecules, hence the contraction force is
reduced.
Surfactants will also adsorb at
the interface between two immiscible liquids such as oil and water and will
orientate themselves with their hydrophilic group in the water and their
hydrophobic group in the oil. The interfacial tension at this interface, which
arises because of a similar imbalance of attractive forces as at the water
surface, will be reduced by this adsorption.
Surface tension of surfactant
solution decreases progressively with increase of concentration, as more and
more surfactant molecule enters the surface or interface. However at a certain
concentration this layer becomes saturated and an alternative mean of shielding
the hydrophobic group from aqueous environment occur through formation of
aggregates called MICELLES .
CLASSIFICATION OF SURFACTANTS:
On Basis of Composition Of Their Tail:
Most surfactants’ “tails” are fairly similar, consisting of a hydrocarbon
chain, which can be branched, linear, or aromatic. Fluorosurfactants have
fluorocarbon chains. Siloxane surfactants have siloxane chains.
On Basis Of Composition Of Head:
There are 4 types of surfactants with a brief review of each as follows.
These classifications are based upon the composition of the polarity of the
head group: nonionic, anionic, cationic, amphoteric
Anionic
surfactants: Anionic surfactants contain anionic
functional groups at their head, such as sulfate, sulfonate, phosphate, and
carboxylates. They are the most commonly used surfactants that account for 50%
of the world production.
They include:
i. Alkali metal and
ammonium soaps:
Surfactants in this group consist mainly of the sodium, potassium or
ammonium salts of long-chain fatty acids, such as:Sodium stearate
ii. Soaps of divalent and
trivalent metals:
Only the calcium salts are commonly used For example calcium oleate
iii. Amine soaps:
Widely used in both pharmaceutical and cosmetic products.
For example:Triethanol amine stearate
iv. Sulphated and sulphonated
compounds:
An example for Alkyl sulphates is sodium lauryl sulphate.
Sulphonated compounds are much less widely used materials of this class
include sodium dioctylsulphosuccinate, and are more often used as wetting
agents or for their detergency
Cationic surfactants:
They account for only 5-6% of
total surfactant production. They are neither good detergents nor foaming
agents and they can not be mixed with formulations which contain anionic
surfactants. But they exhibit two very important features:
Cationic surfactants are basically soaps or detergents, in which the
hydrophilic, or water-loving, end contains a positively-charged ion, or cation.
Typical examples are trimethylalkylammonium chlorides, and the chlorides or
bromides of benzalkonium.
cationic surfactants are attracted to negatively-charged sites that occur
naturally on most fabrics. They can bind to these sites and provide the fabric
with a soft, luxurious feel. For this reason, they are often used as fabric
softeners.
Non-ionic surfactants:
They do not produce ions in aqueous solution. They are compatible with
other types of surfactants. They are much less sensitive to electrolytes than
ionic surfactants and can be used with high salinity or hard water. They are
good detergents, wetting agents and emulsifiers. Some of them have good foaming
properties.
Many long chain alcohols exhibit some surfactant properties. Prominent
among these are the fatty alcohols, cetyl alcohol, stearyl alcohol, and
cetostearyl alcohol
Zwitter ionic or amphoteric surfactants:
They have two functional groups, one anionic and other cationic. It is
the pH which determines which of the groups would dominate; anionic at alkaline
pH and cationic at acid pH. Near isoelectric point, these surfactants display
both charges and are truly amphoteric, often with a minimum of interfacial
activity.
Amphoteric surfactants,
particularly the amino acids are quite biocompatible and are used in
pharmaceuticals and cosmetics. They include:
o Aminopropionic acids
o Imidopropionic acids
o Quaternized compounds
ON BASIS OF COMPOSITION OF
THEIR COUNTER-IONS:
This classification is only for ionic surfactants.
Monoatomic/Inorganic
counter-ions:
·
Cations: Metals e.g. alkali metals, alkaline earth metals, transition
metals.
·
Anions: Halides e.g. chloride, bromide, iodide.
Polyatomic/Organic counter-ions:
Cations: e.g. ammonium ions.
Anions: Tosyls e.g. methyl sulfates, sulfonat
CLASSIFICATION
BASED ON HLB SYSTEM
FUNCTIONAL CLASSIFICATION
As Wetting agent
Wetting is the first step in the dispersion
process. The air that surrounds the solid particles in agglomerate must be
substituted by liquid. Wetting will not occur when the surface tension of the
liquid is too high. A wetting agent does its job because the molecules adsorb
and orient on the liquid-air interface.
Wetting agents
increase the spreading and penetrating properties of a liquid by lowering it’s
surface tension. The wettability of a powder may be described in terms of the
contact angle, which the powder makes with the surface of the liquid. For a
liquid to completely wet a powder, there should be a decrease in the surface
free energy as a result of the immersion process. The wetting agent reduce the
contact angle by decreasing surface tension and interfacial tension and improve
the dispersibility of the powder.
EXAMPLES:
Benzalkonium
Chloride, NF
Poloxamer 188,
NF - P1169
Plant magic plus (it
is a bio wetter)
AS DETERGENT
The dirt/water and solid/water interfacial tensions are lowered and thus
the work of adhesion between the dirt and solid is reduced so that the dirt
particle may be easily detached. Surfactants function by breaking down the interface between water and
oils and/or dirt. They also hold these oils and dirt in suspension, and so
allow their removal. They are able to act in this way because they contain both
a hydrophilic (water loving) group, such as an acid anion, (-CO2- or SO3-) and a hydrophobic (water hating) group, such as an alkyl
chain.
Examples:
Sodium Lauryl Sulfate, Ultrapure:
Sodium
Lauryl Sulfate, Ultrapure, is an organic compound, and anionic surfactant
derived from coconut or palm oils, for use as a detergent. As an
Organosulfate, this salt has the amphiphilic properties needed in
a detergent.
Clorox Healthcare Bleach Germicidal Cleaner:
Clorox Healthcare® Bleach
Germicidal Cleaners are unique, stabilized sodium hypochlorite and detergent
solutions that kill pathogens fast - with a one-minute contact time for a broad
range of microorganisms
AS FOAMING AND ANTI-FOAMING
FOAMING
Persistent foams are formed by solutions of
surfactants. The film in such foams consists of two monolayers of adsorbed
surface active molecules separated by an aqueous core. The surfactants
stabilize the film by means of electrical double layer repulsion or steric
stabilization.
Repulsion can
result from two mechanisms that may either be used separately or in
combination:
- Electrostatic stabilisation:
all particles carry a charge of the same sign.
- Steric
stabilisation: all particles are covered with tails
dissolving in the liquid that surrounds the particles
.
ANTI FOAMING:
Surface active agents act by lowering the
surface tension over small regions of the liquid film. These regions are
rapidly pulled out by surrounding regions of higher tension, small areas of
film are therefore thinned out and left, without the properties to resist
rupture.
EXAMPLES:
Hydrazine Dihydrochloride, Reagent
Hydrazine
Dihydrochloride, Reagent has a systematic name of diazane and is an inorganic
compound. It is primarily used as a foaming agent in
making polymer foams
Simethicone, USP
Simethicone,
USP is an antifoaming agent that is used to reduce
bloating from excessive gas.
Antifoam A
Antifoam A is also known as polydimethylsiloxane and is part of
a group of polymeric organosilicon compounds known as silicones. It is a
chemical additive that reduces and hinders the formation of foam in industrial
process liquids.
As EMULSIFYING AGENT
Emulsions are stabilized by adding an emulsifier or emulsifying agents.
These agents have both a hydrophilic and a lipophilic part in their chemical
structure. All emulsifying agents concentrate at and are adsorbed onto the
oil:water interface to provide a protective barrier around the dispersed
droplets. In addition to this protective barrier, emulsifiers stabilize the
emulsion by reducing the interfacial tension of the system. Some agents enhance
stability by imparting a charge on the droplet surface thus reducing the
physical contact between the droplets and decreasing the potential for
coalescence.
Some commonly used emulsifying agents include tragacanth, sodium lauryl
sulfate, sodium dioctyl sulfosuccinate, and polymers known as the Spans and
Tweens.
EXAMPLES:
Brij(R) C2
Brij(R) C2 is
non-ionic surfactant of the polyethylene glycol family. It is used as a
solubilizer and emulsifying agent in foods,
cosmetics, and pharmaceuticals.
Polysorbate 20, Electrophoresis Grade
Polysorbate
20, Electrophoresis Grade is a frequently used member of the polysorbate
family. These have been used as emulsifying agents for
the preparation of stable oil in water emulsions
Stearic Acid, Type 50, Powder, NF
Stearic Acid,
Type 50, Powder, NF is used as an emulsifying agent, solubilizing agent, tablet
and capsule lubricant. The NF grade indicates it is graded suitable for
personal care, cosmetic and pharmaceutical applications.
As DISPERSING , SUSPENDING AND DEFLOCULATING AGENT:
Solid particles attract each other. For this reason, energy is needed to
separate the particles from each other in the second step of the dispersion
process. Also, solid particles must be stabilised after they have been
separated from each other. The particles will move to each other and glue
together again when particle-particle repulsion is insufficient. The
spontaneous process of gluing together of solid particles in a liquid is
called flocculation. The functionality of a dispersant is
to prevent flocculation. Dispersants do their job because the molecules adsorb
on the solid-liquid interface and assure repulsion between the particles.
The
balance of forces appears depend on both the thickness and the concentration of
the polymer in the adsorbed layer.
| EXAMPLES: |
Ferrous Chloride, Crystal, Technical
Ferrous
Chloride, Crystal, Technical is used in the laboratory synthesis of iron
complexes and as a reducing flocculating agent in
wastewater treatment,
Agar, Powder, NF
Agar, Powder,
NF is used in the pharmaceutical industry for many applications such as a suspending agent, surgical
lubricants and in preparations of emulsions, suspensions and capsules
Bentonite, Powder, NF
Bentonite,
Powder, NF is used as suspending and emulsifying agent.
As SOLUBLIZING AGENT :
Water insoluble or partly soluble substances
are brought into aqueous solution by incorporation into micelles, is termed
solublization.
EXAMPLES:
Ethyl Oleate, NF
Ethyl Oleate, NF is used as a solubilizing agent in
pharmaceutical preparations.
Benzalkonium Chloride, NF
Benzalkonium Chloride, NF is used in the
pharmaceutical industry as an antimicrobial preservative, antiseptic,
disinfectant, solubilizing agent, and
wetting agent.
OTHER
SURFACTANTS:
SILICON SURFACTANTS
Silicone surfactants are organo-modified
branched silicone polymers with many “heads” and many
“tails”.
This makes them more efficient than
other surfactants, and more cost effective to use. Silicone
polyethers are good examples:
In search of molecular “happiness”
Surfactants are drawn to interfaces – the
boundaries between two different liquids. Interfaces are the only place where
both parts of the surfactant molecule can find “true happiness.”
Because the hydrophilic part of the
surfactant is highly soluble in water and the hydrophobic part is highly
soluble in oil, the surfactant engulfs and stabilizes droplets of one liquid
within the other.
The two most common emulsions are
water-in-oil and oil-in-water.
Since Si is a heavier atom than
C, a similar hydrophibicity is attained with less Si atoms than C atoms.
Essentially all surfactant types can be made with a silicon based hydrophobic
tail by replacing several C atoms by one Si atom or one dimethyl-siloxane
group.
Silicones
love interfaces – all kinds of interfaces – liquid-liquid, solid-solid,
liquid-solid, liquid-gas, solid-gas.
EXAMPLES:
Dimethylpolysiloxane, Technical
Dimethylpolysiloxane,
Technical, also known as polydimethylsiloxane, is a silicon-based surfactant used
in defoamers for over-the-counter drugs and personal care products.
Polydimethylsiloxane, Silanol Terminated
Polydimethylsiloxane,
Silanol Terminated is a silicon-based organic polymer with an average molecular
weight of 70,000 - 80,000. It is used in cosmetic and personal care products as
a surfactant and conditioning agent.
FLUORINATED
SURFACTANTS
Hydrogen atoms of the surfactant hydrocarbon tail can be
substituted by halogens, particularly F.
Capstone fluorosurfactants enable simplified formulations and higher performance
end-products. For applications such as paints and coatings, adhesives, waxes
and polishes, and industrial cleaning products, Capstone™ fluorosurfactants
enhance the properties of formulations by improving properties, such as wetting
and spreading, leveling, penetrating, foaming control, and substantially
reducing surface tension.
Examples:
Flexiwet NF:
anionic fluorosurfactant with
exceptional wetting properties and excellent chemical and thermal stability.
Thetawet FS-8400 is a water-soluble,
amphoteric fluorosurfactant in a glycol stabilized aqueous solution.
Excellent choice for wetting difficult to wet, low energy surfaces.
POLYMERIC
SURFACTANTS:
Polymeric surfactants or
surface active polymers, which result from the association of one or several macromolecular structures exhibiting
hydrophilic and lipophilic
characters, either as
separated blocks or
as grafts. They
are now very
commonly used in formulating products
as different as
cosmetics, paints, foodstuffs,
and petroleum production additives.
These surfactants have many uses, in particular as colloid and
nanoemulsion dispersants, wetting agents, detergents and even additive to
dehydrate crude oils.
Examples:
Tergitol(R) XH, Surfactant
Tergitol(R)
XH, Surfactant is an alkyl EO/PO copolymer, nonionic surfactant with
excellent steric and freeze/thaw stabilizing benefits for use in a wide variety
of applications including iodophors and emulsion polymerization.
Atlox
This new molecule is a high molecular
weight polymeric emulsifier and dispersant with low HLB, developed to provide
excellent stability when used in a variety of formulations.
Polyglycosidic surfactant:
Example: TRITON CG-425 is readily biodegradable
Alkyl Polyglucoside, non ionic surfactant.
It is
Excellent wetting properties and
Excellent reduction of surface
tension. It is made from renewable materials (including alcohols derived from
natural sources and sugar) and readily
biodegradable.
Recommended Applications • Hand Dishwash Detergents • Hard Surface Cleaners.
Novel surfactant (Gemini surfactant):
They are the
group of novel surfactants with more than 1 hydrophilic head group and
hydrophobic tail group linked by a spacer at or near the head groups.
It has unique
properties of Gemini surfactant such as good water solubility, unusual micelle
structure and high efficiency in reducing oil/water interfacial tention and low
CMC.
They are
potentially used as cleaning agent, detergent, cosmetic and personal care etc.
| EXAMPLE: |
Siloxane based multifunctional additives
MICELLES
A micelle is an aggregate of surfactant molecules dispersed in a liquid
collid. The process of forming micelle is known as micellization. The surface
tension of a surfactant solution decreases progressively with increase of
concentration as more surfactant molecules enter the surface or interfacial
layer. However, at a certain condition this layer becomes saturated and an
alternative means of shielding the hydrophobic group of the surfactant from the
aqueous environment occurs through the formation of aggregates of colloidal
dimension called micelles.
CMC
The concentration of the monomer at which the micelles are start to form
in solution at particular temperature is termed the critical micelle
concentration.
Properties of Micelles
Ø Most micelles are spherical and contain between 60 and 100
surfactant molecule.
Ø Micelles are dynamic structures and are continually formed and
broken down in solution – they should not be thought of as solid spheres.
Ø The typical micelle diameter is about 2–3 nm and so they are not
visible under the light microscope.
Ø There is an equilibrium between micelles and free surfactant
molecules in solution. When the surfactant concentration is increased above the
CMC, the number of micelles increases but the free surfactant concentration
stays constant at the CMC value.
a)
Structure of the micelles formed by ionic surfactants
The structure of the micelles
formed by ionic surfactants consists of:
HYDROPHOBIC CORE composed of hydrocarbon chain
A STERN LAYER surrounding core, which is
concentric shell of hydrophilic head
A GOUY CHAPMAN ELECTRICAL DOUBLE LAYER
surrounding the stern layer, it is a diffuse layer containing counter ions
required to neutralize the charge on micelle.
b)
Micelles formed by non-ionic surfactants:
Micelles formed by non-ionic
surfactants are larger than their ionic counterparts and may sometimes be
elongated into an ellipsoid or rod-like structure have a hydrophobic core
formed from the hydrocarbon chains of the surfactant molecules surrounded by a
shell (the palisade layer) composed of the oxyethylene chains of the surfactant
, which is heavily hydrated
c)
Micelles formed in non-aqueous solution: (reverse or inverted
micelles) have a core composed of the hydrophilic groups surrounded by a shell
of the hydrocarbon chains.
Factors affecting CMC:
1. Structure of
Hydrophobic Group:
Increasing the hydrophobic part
of the surfactant molecule favors the micelles formation. i.e. CMC value is
decreased and a corresponding increase in micellar size.
2. Nature of Hydrophilic
Group:
Nonionic surfactants generally
have very much lower CMC values than their ionic counterparts with similar
hydrocarbon chain.
3. Type of Counter Ion:
Ionic surfactants with organic
counter ions have lower CMC than those with inorganic counter ions.
4. Addition of
Electrolytes:
Electrolyte addition to solution
of ionic surfactants decreases the CMC and increase the micellar size.
5. Temperature:
Aq. Solutions of many non- ionic
surfactants become turbid at a characteristic temperature called Cloud Point.
At Cloud Point there is increase in micellar size and decrease in CMC. This
cloudy appearance is reversed on cooling. Temperature has comparatively less
effect on micellar properties of ionic surfactants.
Pharmaceutical Applications of surfactants:
(1)
Surfactants in Solid Dosage Forms:
Surface-active agents have been
widely shown to enhance drug dissolution rates.This may be due to wetting
effects, resulting in increased surface area, effects on solubility and
effective diffusion coefficient or a combination of effects. Consequently
surfactants have been included in tablet and capsule formulations to improve
wetting and deaggregation of drug particles and thus increase the surface area
of particles available for dissolution. This wetting effect is found to be
operative at concentrations below the CMC.
(2)
Surfactants in Semi Solid Systems:
Surfactants are major
constituents of pharmaceutical, cosmetic, and food semisolid formulations, many
of which are emulsions, either oil in water (o/w) or water in oil (w/o). They
are included for their stabilizing, wetting, solubilizing, detergent and
penetration enhancing properties. Emulsion formulation: Water-in-oil emulsions
traditionally contain surfactants of natural origin such as cholesterol, wool
fat, wool alcohols, lanolin, divalent salts of fatty acids soaps, calcium
oleate and/or synthetic agents of low hydrophilic-lipophilic balance (HLB)
(indicating high lipophilicity), such as Spans (fatty acid esters of
sorbitan).The water soluble surfactant may be anionic (e.g., sodium lauryl
sulphate), cationic (e.g., cetrimide), or non-ionic (e.g., cetomacrogol,
Tweens). Mixed emulsifiers control the consistency of a cream by forming a
viscoelastic network throughout the continuous phase of the emulsion. The
network results from the interaction of the mixed emulsifier with water,
forming a liquid crystalline phase. (Abramzom AA. REVIEWS-SURFACTANTS THEIR
PROPERTIES AND USE). Solubilisation
of drugs (for example, steroids and waterinsoluble vitamins), and essential
oils by non-ionic surfactants (usually polysorbates or polyoxyethylene sorbitan
esters of fatty acids).[17]
Formulation of Ointments: Ointments are semisolid preparation meant
for external application to skin or mucous membrane; they usually contain
medicaments or medicaments in dissolved, suspended or emulsified in an ointment
base. Sometimes in the ointment preparation surfactants are useful for the easy
removal from the skin by washing with water & also for the consistency by
reduction of surface tension. Surfactants are also used in formulation of cold
cream, cleansing cream, vanishing cream, shaving cream or any media. (Corrigan
OI, Healy AM. Surfactants in Pharmaceutical Products and Systems.)
(3) Surfactants as
enhancers for percutaneous absorption:
An approach to enhance
penetration of drugs through skin is to use the surfactants as penetration
enhancers for accelerating drug absorption through stratum corneum. E.g.
phospholipids, polysorbates, sorbitan esters. Penetration is enhanced through
interaction with skin cells or through changing the physicochemical properties
of formulated drug like solubility, diffusion rates etc. Sodium dodecyl
sulphate is a powerful surfactant that denatures and unfold keratin proteins
leading to a porous structure through which drugs can diffuse easily.
(4) Surfactants in mouth
washes:
Mouthwashes are aqueous solutions often in
concentrated form containing one or more active ingredients or excipients. They
are used by swirling the liquid in the oral cavity. Mouthwashes can be used for two purposes.
They are therapeutic and cosmetic.
Therapeutic mouth rinses or washes can be formulated In order to reduce
plaque, gingivitis, dental caries, and stomatitis. Cosmetic mouthwashes may be
formulated to reduce bad breath through the use of antimicrobial and/or
flavouring agents. Surfactants are used because they aid in the solubilization
of flavours and in the removal of debris by providing foaming action. (Reshad
M, Nesbit M, Petrie A, SetchellD.Eur J ProsthodontRestor Dent. 2009).For
example in Act cool splash mint mouth wash polysorbate 20 surfactant is used.
(5) Surfactants in
respiratory distress therapy:
There is a natural lung
surfactant produced in our bodies, majorly composed of phospholipids and is gel
like, it covers alveolar walls and is constantly renewed. If it is absent there
is tension in alveolar walls and lungs can collapse. Neonates do not have this
surfactant until birth and often suffer from neonatal respiratory distress
syndrome. It is treated by using some exogenous surfactant along with
supplemental oxygen and decreases tension of walls. One of the most important
pharmaceutical pulmonary surfactant is Survanta or its generic form Beraksurf
produced by Abbvie and Tekzima
respectively.
(6) Surfactants in
suppository bases:
Several non-ionic surface-active materials
have been developed as suppositories vehicles. Many of these bases, known as
water-dispersible bases, can be used for the formulation of both water-soluble
and oil soluble drugs. The surfactants most commonly used are the
polyoxyethylenesorbitan fatty acid esters (Tweens), the polyoxyethylene
stearates, and the sorbitan fatty acid esters (Spans). The stainless steel
molds are lubricated prior to dipping into the gelatin solution and sodium
lauryl sulphate is added to reduce the surface tension of the mix and cause the
mold pins to wet more uniformly. Surface-active agents are widely used in
combination with other suppository bases. The inclusion of these agents in the
formulation may improve the wetting and water-absorption properties of the
suppository. In addition, emulsifying surfactants help to keep insoluble
substances suspended in a fatty base suppository. The inclusion of a surfactant
in the suppository formulation may enhance the rectal absorption of drugs.
(Corrigan OI, Healy AM. Surfactants in Pharmaceutical Products and Systems).
(7) Surfactants in
suspension aerosols:
The addition of surfactants to
aerosol suspensions has been most successful. These surfactants exert their
activity by coating each of the particles in suspension and orients at the
solid-liquid interface. Agglomeration is reduced, thereby increasing stability
by providing a physical barrier. Those surfactants having an HLB less than 10,
could be utilized for aerosol dispersions..
(8) Surfactants in water
based aerosols:
Water-based aerosols contain
relatively large amount of water. Surfactants have been used to a large extent
to produce a satisfactory homogenous dispersion. Surfactants that possess low
water solubility and high solubility in nonpolar solvents have been found to be
most useful. Long chain fatty acid esters of compounds including glycols,
glycerol, and sorbitol exemplify this series.
(9) Surfactants for contact
lens cleaning:
Surfactants act as cleansers,
which emulsify accumulated oils, lipids and inorganic compounds over contact
lenses. Surfactant agents are utilized either within a mechanical washing
device or by placing several drops of the solution on the lens surface and
gently rubbing the lens back and forth with the thumb and fore finger (about 20
to 30 seconds).
(10) Surfactants in hard
gelatin capsules:
In an experiment benzoic acid as
loose powder was filled into a size 00 and a size 1 capsule. The slowest
dissolution rate was obtained with the size 1 capsule in which the powder is
most tightly packed. They overcome this problem by adding 0.5% of polyol
surfactant into the formulation. This greatly improved the dissolution rate
which they showed was due to an increase in the deaggregation rate of the
material.
(11) Surfactants as cerumen
removing solutions:
Cerumen is a combination of the
secretions of sweat and sebaceous glands of the external auditory canal.The
secretions, if allowed to dry, form a sticky semisolid which holds shredded
epithelial cells, fallen hair dust and other foreign bodies that make their way
into the ear canal. Excessive accumulation of cerumen in the ear may cause
itching, pain, impaired hearing and is a deterrent to otologic examination
.Through the years, light mineral oil, and hydrogen per oxide have been
commonly used agents to soften impacted cerumen for its removal. Recently,
solutions of synthetic surfactants have been developed for their cerumenolytic
activity in the removal of ear wax. A commercial product utilizes carbamide
peroxide in glycerin/propylene glycol. On contact with the cerumen, the
carbamide peroxide releases oxygen which disrupts the integrity of the impacted
wax, allowing its easy removal.Tri ethanolamine polypeptide oleate- condensate,
commercially formulated in propylene glycol, is used to emulsify the cerumen
thereby facilitating its removal (Cerumenex drops). Brands in pakistan ABBOWAX
drops, CARBOWAX drops. (Dimmitt P.J Pediatr. Health Care. 2005 Sep-Oct;)
(12) Surfactant influencing
drug absorption:
Surfactants influences drug
absorption from the gastrointestinal tract in humans. Surfactant monomers can
potentially disrupt the integrity and function of a membrane. Hence, such a
membrane disrupting effect would tend to enhance drug penetration and hence
absorption across the gastrointestinal barrier.
The ability of a surfactant to
reduce the solid/liquid interfacial tension will permit the gastrointestinal
fluids to wet more effectively and to come into more intimate contact with the
solid dosage forms.
(13) Surfactants in
parenteral dosage forms:
Surfactants in parenterals can increase drug
solubility through micellization, improve drug wetting, prevent drug
precipitation upon injection, improve stability of drug in solution etc.
Commonly used surfactant in parenterals is polysorbate 80.
(14) Ophthalmic delivery:
Surfactants are sometimes used in
topical eye products for dispersing insoluble ingredients or to aid in
solubilisation. They are used in smallest concentration since they can be
irritating to sensitive ocular tissues. Non-ionic surfactants are less
irritating. Polysorbate 80 is used in preparation of an ophthalmic emulsion.
(15) Pulmonary systemic drug
delivery:
Pulmonary systemic drug delivery
takes advantage of the large surface area of the alveoli, the low enzymatic
activity in the lungs, and their rich vascular system to deliver different
drugs, especially those of high molecular weight (such as peptides and
proteins). To successfully deliver through the lungs, there is a need to use
absorption enhancers. Surfactants such as bile salts are used as such
enhancers.Surfactants are found in both solution and suspension formulations of
metered dose inhalers (MDIs).The most common surfactants found in pressurized
aerosol preparations include sorbitantrioleate (Span 85), oleic acid, and Lecithin These agents are non-volatile
liquids which dissolve in the propellant blend. Their function in the
formulation is to provide lubrication for the metering valves and, in the case
of suspension formulations, to maintain the disperse nature of the drug.
(16) Buccal and sublingual
systemic delivery of drugs:
Buccal and sublingual systemic
delivery is a useful alternative administration route through oral
mucosa.Penetration enhancing surfactants for example sodium dodecyl sulfate are
used to achieve adequate absorption of large molecules. Medicated chewing gum
preparations may contain solubilizers, such as lecithin, polysorbates.For
example pepsid chewable tablets.
(17) Formulation of Shampoo:
Shampoo is a hair care product used for the removal of
oils, dirt, skin particles, dandruff, environmental pollutants and other
contaminant particles that gradually build up in hair. The goal is to remove
the unwanted build-up without stripping out so much as to make hair
unmanageable. Shampoo, when lathered with water, is a surfactant, which, while
cleaning the hair and scalp, can remove the natural oils (sebum) which
lubricate the hair shaft. (Corrigan OI, Healy AM. Surfactants in Pharmaceutical
Products and Systems) .
Sodium
laureth sulfate (SLES) and its chemical cousin sodium lauryl sulfate
(SLS) are commonly used surfactants (wetting agents) and detergents, often
used in diluted form in personal care products like shampoos and body washes.
Revlon uses these ingredients in its shampoos. The current science confirms
these ingredients are safe for their intended use. At least three different
agencies (the Occupational Safety and Health Administration (OSHA), the
National Toxicology Program (NTP), and the International Agency for Research on
Cancer (IARC)) have all rated these ingredients as non-carcinogenic.
REFERENCES :
1.
Comprehensive
pharmacy review for NAPLEX/ editors,Leon shargel.. [et al.]- 8th ed.
2.
Ansel's
pharmaceutical dosage forms and drug delivery systems /Loyd V. Allen Jr.,
3.
Nicholas
G. Popovich, HowaC. Ansel. - - - 9th ed.
4.
Pharmaceutics: Basic Principles and Application to
Pharmacy Practice by Alekha Dash, Somnath Singh,
Justin Tolman
5.
Rosen
MJ &Kunjappu JT (2012). Surfactants and Interfacial Phenomena (4th ed.). Hoboken, New Jersey: John Wiley & Sons. p. 1.ISBN 1-118-22902-9.
7.
http://www.mpikg.mpg.de/886719/MicelleFormationn
8.
Applications of Surfactants in Pharmaceutical
Dosage Forms ShlomoMagdassi, Alexander
Kamyshny, and Katy Margulis-Goshen Handbook of Detergents, Part E. Oct 2008 ,
455 -468
9.
P.Muthuprasanna
J.et al /Int.J.PharmTech Res.2009,1(4)
10. Remington, Joseph P.2006. Remington, the
science and practice of pharmacy. Easton, Pa: Mack Pub. Co.
15.
Surfactants, the essential chemical industry,
centre for industry education corporation et al, 2013.
16.
Spectrum chemical mfg group, et al, 2017
17.
The difference between wetting agents and
dispersants by jochum beetsma et al, 2015
18.
Controlling oil aeration and foam by marine
duncanson et al, 2016.
21. Surfactants by sachin patel et al, 2016
22. Silicon surfactants by Dow corning et al,
1943
23.
Capstone
by chemorous compny et al, 2017
24.
Fluorinated
surfactants Innovative chemical technologies, inc. et al, 2017
25.
Polymeric surfactants by M.R Porter et al,
1991
26.
Polymeric surfactants by croda
28.
https://www.researchgate.net/file.PostFileLoader.html?id...assetKey...
29. Slideshare.com
Moderization
of surfactant chemistry in the age of Gemini and bio-surfactants by
Monohar
Hossain MondalSusanta
MalikAnkit Roy
Congratulation for the great post. Those who come to read your Information will find lots of helpful and informative tips.h2eau waters.
ReplyDelete