This presentation is very much helpful for the medical students,pharmacists, researchers and other health care providers. i hope it will provide important information regarding surfactants and their applications in pharmaceutical dosage forms.

1. Surfactants and their applications in pharmaceutical
Dosage forms
Prepared by: Muhammad Jamal
Email : jamalkhan616@gmail.com
Contact: +923469054015

2. * Surfactants
Surfactants are termed as surface-active agents also wetting agents,
emulsifying agents or suspending agents depending on its properties and use.
Surface-active agents are substances which, at low concentrations, adsorb onto
the surfaces or interfaces of a system and alter the surface or interfacial free
energy and the surface or interfacial tension.
Surfactants are monomers, it has a characteristic structure possessing both
hydrophobic groups / non-polar regions (their "tails") usually contain a C12–
C18 hydrocarbon chain and hydrophilic groups / Polar Regions(their "heads").
Therefore, they are soluble in both organic solvents and water, so they called
amphiphilic.
(Martin Alfred. Physical Pharmacy-Physical Chemical principles in Pharmaceutical Sciences.). (Perkins Warren S. )

3. Fig.no.1. Surfactant (Monomer) Head - Polar, Hydrophilic
Tail - Non polar, Hydrophobic
Hydrophilic head
Hydrophobic tail

4. Sodium dodecyl sulphate .The polar "head" has affinity for water and the "tail" has affinity for oil

5. Mechanism of Action
Surfactants can work in three different ways:
Roll-up, Emulsification and Solubilization.
(a) Roll-up mechanism: The surfactant lowers the oil/solution and
fabric/solution interfacial tensions and in this way lifts the stain of the
fabric.
(b)Emulsification: The surfactant lowers the oil solution interfacial
tension and makes easy emulsification of the oil.
(c)Solubilization: Through interaction with the micelles of a
surfactant in a solvent (water), a substance spontaneously dissolves
to form a stable and clear solution.

6. Fig. Surfactant mechanism of action in stain removal from fabric

7. Classification of surfactants:
Surfactant can be classified based on charge groups present in their head. A
nonionic surfactant do not have any charge groups over its head. The head of an
ionic surfactant carries a net charge. If the charge is negative, the surfactant is more
specifically called anionic and if the charge is positive, it is called cationic.
If a surfactant contains a head with two oppositely charged groups, it is termed
zwitterion.
1. Anionic surfactants
2. Cationic surfactants
3. Non-ionic surfactants
4. Zwitterionic/ amphoteric surfactants

8. (a)Anionic surfactants:
In solution, the head is negatively charged.
These surfactants are the most widely used
type of surfactant for preparing shampoos
because of its excellent cleaning properties
and high hair conditioning effects. Anionic
surfactants are particularly effective at oil
cleaning and oil/clay suspension.

9. The most commonly used anionic surfactants are alkyl sulphates, alkyl
ethoxylate sulphates and soaps. Most of the anionic surfactants are
carboxylate ,sulfate and sulfonate ions .(ARG Remington ,The science and practice of
pharmacy ,19th edn ,Vol 1) . The straight
chain is a saturated /unsaturated C12-C18 aliphatic group. The water
solubility potential of the surfactant is determined by the presence of
double bonds. (G.Zagrafti .The science and practice of pharmacy)

10. (b) Cationic Surfactants:
In solution, the head of the cationic surfactant is positively charged. Cationic
surfactants are quaternary ammonium compounds and they are mostly used for
their disinfectant and preservative properties as they have good bactericidal
properties. They are used on skin for cleansing wounds or burns. Mostly used
cationic surfactants are cetrimide which has tetradecyl trimethyl ammonium
bromide with minimum amount of dodecyl and hexadecyl compounds . Other
cationic surfactants are benzalkonium chloride,cetylpyridinium chloride etc.

11. (c) Non-Ionic Surfactants:
 Those surfactants do not have any electrical charge, which makes them resistant to
water hardness deactivation.
 They are less irritant than other anionic or cationic surfactants.
 The hydrophilic part contains the polyoxyethylene ,polyoxypropylene or polyol
derivatives.
 The hydrophobic part contains saturated or unsaturated fatty acids or fatty alcohols
They are excellent grease/oil removers and emulsifiers.

12. The non ionic surfactant can be classified as
• Polyol esters ,
• polyoxyethylene esters ,
• poloxamers .
 The Polyol esters includes glycol and glycerol esters and sorbitan
derivatives.
 Polyoxyethylene esters includes polyethylene glycol (PEG 40,PEG -50
,PEG- 55).
 The most commonly used non-ionic surfactants are ethers of fatty
Alcohols.
(Zhang W, Dai X et al)

13. (d) Amphoteric/Zwitterionic Surfactants:
 These surfactants are very mild, making them particularly suited for use in
personal care preparations over sensitive skins.
 They can be anionic (negatively charged), cationic (positively charged) or
non-ionic (no charge) in solution, depending on the acidity or pH of the
water.
 Those surfactants may contain two charged groups of different sign.
Whereas the positive charge is almost always ammonium but the source of
the negative charge may vary (carboxylate, sulphate, sulphonate).
 These surfactants have excellent dermatological properties. They are
frequently used in shampoos and other cosmetic products, and also in hand
dishwashing liquids because of their high foaming properties.
(Zhang W, Dai X et al)

14. Amphoteric Surfactant

15. PROPERTIES OF SURFACTANT
• Wetting of Solids
• Solubilization
• Emulsification
• Dispersion of solid in solution
• Micellization
• Detergency
( Rawlins EA, editors. Bentley’s Text book of Pharmaceutics).
(Faeder J et al)

16. • Micellization
 Definition- A micelle is an aggregate of surfactant molecules dispersed in
a liquid colloid. The process of forming micelle is known as micellization.
 Micelle formations in polar and non-polar solvent depend on the
concentration of the surfactant in the particular solvent.
 If add surfactant (monomers) in solvent, at low concentration some
monomers dispersed in solvent or aggregate at the surface or interface until
all surface or interface saturated by surfactant.
 Further addition of surfactant increase concentration of monomers and it
goes in solvent and start to form micelles. This concentration is called
CMC. [Critical micelle concentration]

17. CMC- The concentration of monomer at which the micelles are start to form in
solvent at particular temperature. Micelles form only when the concentration of
surfactant is greater than the critical micelle concentration (CMC).
(Tanford C. The hydrophobic effect: Formation of micelles and biological membranes.)

18. Wetting of Solids
o A drop of liquid when placed on a flat, homogeneous solid surface comes
to equilibrium, assuming a shape which minimizes the total free energy of
the system.
o The angle between the liquid and the solid is called the contact angle (θ),
the angle being measured through the liquid.
o The contact angle may be calculated if the surface and interfacial tensions
are known from Young’s equation given in Eq. (1) or (2).
o γSA = γSL + γLA cos θ ______________________________(1)
Or
o Cosθ = γSA – γSL / γLA ______________________________(2)
Where γLA is the surface tension of the liquid, γSL is the interfacial tension
existing between the solid and liquid phases, and γSAis the surface tension (or
surface free energy) of the solid.

19. o The term ‘‘wetting agent’’ is applied to any substance that increases
the ability of water or an aqueous solution to displace air from a
liquid or solid surface.
o For good wetting, cosθ should be as close as possible to 1; that is, θ
should be as close as possible to 0.
If θ< 90, wetting of the solid is said to take place. If θ> 90, wetting
does not take place.

20. Fig.no.9. Contact angles of liquid on surface.

21. Emulsification
 This is the property of surfactants to form a stable emulsion of two or more
immiscible liquids.
 When oil and water mixed together and agitated, droplets of varying size are
produced.
 Tension exists at the interface because the two immiscible liquid phases tend to
have different attractive forces for a molecule at the interface.
 Molecules of one phase are repelled by other phase due to greater interfacial
tension, but for dispersion of liquid necessary of reduction of interfacial
tension.

22. This is done by addition of surfactants and having following mechanisms.
• Reduction of interfacial tension – Thermodynamic stabilization.
• Formation of interfacial film – mechanical barrier to coalescence.
• Formation of electrical double layer – electrical barrier to approach of
particles.

23. ♦ Interfacial Tension
Even though reduction of interfacial tension lowers the interfacial free energy
produced on dispersion. Surfactants are adsorbing on the interface of them, because
hydrophilic head have affinity towards water and hydrophobic tail towards oil. This
is responsible for reduction of interfacial tension and two immiscible phases are
become miscible.
♦ Interfacial Film
The formation of film by the emulsifier is similar to adsorption of surfactants at the
interface of an oil and water. If the concentration of emulsifier is high enough, it
forms a rigid film between the immiscible phases which act as a mechanical bar to
both adhesion and emulsifier of emulsion droplets. In O / W emulsions, the mixture
of sodium cetyl sulfate and cholesterol form more stable interfacial film.

24. ♦ Electrical Repulsion / Electrical Double Layer
It has just been described how interfacial films significantly alter the
rate of coalescence of droplets by acting as barriers. In addition, the
same or similar film can produce repulsive electrical forces between
approaching droplets. Such repulsion is due to an electrical double
layer, which may arise from electrically charged groups oriented on
the surface of emulsified globules.

25. * Solubilization
• Solubilization can be defined as ‘‘the preparation of a thermodynamically stable
isotropic solution of a substance normally insoluble or very slightly soluble in a
given solvent by the introduction of an additional amphiphilic component or
components.
• ’’ The amphiphilic components (surfactants) must be introduced at a
concentration at or above their critical micelle concentrations.
• Simple micellar systems (and reverse micellar) as well as liquid crystalline
phases and vesicles referred to above are all capable of solubilization.
• In liquid crystalline phases and vesicles, a ternary system is formed on
incorporation of the solubilizate and thus these anisotropic systems are not
strictly in accordance with the definition given above.

26. Solubilization by micelles
The location of a solubilized molecule in a micelle is
determined primarily by the chemical structure of the
solubilizate.
Solubilization can occur at a number of different sites in a
micelle:

27. Fig : In Aqueous Systems Solubilization Of Drugs At Diff. Positions Of Micelle.
1. On the surface, at the micelle–solvent interface,
2. At the surface and between the hydrophilic head groups,
3. In the palisades layer, i.e., between the hydrophilic groups and the first few
carbon atoms of the hydrophobic groups that comprises the outer regions of the
micelle core.
4. More deeply in the palisades layer, and in the micelle inner core.
( Loyd V Allen et al)

28. Examples
1. Polar alcohols are soluble in aqueous solution, so it located in solution / on
surface of micelle.
2. Phenol are having polar –OH group and non polar benzene ring. In which –OH
gr. Located in hydrophilic environment and benzene ring in hydrophobic
environment, so it located at the surface and between the hydrophilic head groups.
3. Semi polar materials, such as fatty acids are usually located in the palisades
layer, the depth of penetration depending on the ratio of polar to non-polar
structures in the solubilisate molecule.
4. Non-polar additives such as hydrocarbons tend to be intimately associated with
the hydrocarbon core of the micelle.
(Kwon GS, Kataoka K. Block copolymer micelles as long circulating drug vehicles.)

29. Pharmaceutical Examples of solubilization
• The solubilization of phenolic compounds such as cresol, chlorocresol,
chloroxylenol and thymol with soap to form clear solutions for use in
disinfection.
• Solubilized solutions of iodine in non-ionic surfactant micelles
(iodophors) for use in instrument sterilization.
• Solubilization of drugs (for example, steroids and water insoluble
vitamins), and essential oils by non-ionic surfactants (usually polysorbates or
polyoxyethylene sorbitan esters of fatty acids).
( Malmsten M. “Surfactants and polymers in drug delivery system”,)

30. Detergency
It is most important property of surface active agents. Surface active agents are
referred as detergents. The term Detergency is mostly used in the cleaning /
removing of grease, oil and dirt from the solid surface. The principle of detergency is
based on the formation of micelle.
The process needs many of the actions specific to surfactant molecules.
1. The surfactant requires good wetting properties to ensure good contact with the
solid surface.
2. It also has the ability to remove dirt into the bulk liquid.

31.  This property is achieved by lowering the surface tension of the medium in
which surfactants is dissolved.
 By lowering this interfacial tension between two media or interfaces (e.g.
air/water, water/stain, stain/fabric) the surfactant plays a key role in the
removal and suspension of dirt.
 The lower surface tension of the water makes it easier to lift dirt and grease
off of dirty dishes, clothes and other surfaces, and help to keep them
suspended in the dirty water.
 The water-loving or hydrophilic head remains in the water and it pulls the
stains towards the water, away from the fabric.

32.  The surfactant molecules surround the stain particles, break them up and
force them away from the surface of the fabric.
 They then suspend the stain particles in the wash water to remove them.
If the dirt is oily it may be emulsified or solubilized by the surfactant.
(Liberman et al, Lachaman et al, Allen Loyd V et al)

34. APPLICATION OF SURFACTANTS
IN PHARMACEUTICALS

35. 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.

36.  However they also reduce the effective rate of drug diffusion as a
consequence of drug solubilization within micelles.
 The effect of surfactants on the dissolution of solids is complex. In
addition to effects on the available surface area, surfactants in
concentrations above the CMC can increase drug solubility and hence the
effective concentration gradient.

37. I. Hard Gelatin Capsules and Tablets
Wetting agents : Surfactants are used in capsule and tablet formulations as wetting
agents to aid dissolution.
Lubricants, anti-adherents, and glidants.
 The primary function of tablet lubricants is to reduce the friction arising at the
interface of tablet and die walls during compression and ejection.
 Lubricants also possess antiadherent (prevention of sticking to the punch and,
to a lesser extent, to the die wall) and glidant (improvement of flow
characteristics of powders or granulates) characteristics and are useful in the
processing of hard gelatin capsules.
 Magnesium stearate is used extensively as a lubricant in tablet manufacture. It
is an example of a ‘‘boundary lubricant,’’ that is, the polar regions of the
molecule adhere to the metal surface of the die wall (in tablet manufacture).

38.  Lubricants may be classified as water-soluble or water-insoluble. The latter are
generally more effective than water-soluble lubricants and can be used at a
lower concentration.
 Common water-insoluble lubricants (which are surfactants) include
magnesium stearate, calcium stearate, sodium stearate, and stearic acid;
 water-soluble lubricants include sodium lauryl sulphate and magnesium lauryl
sulphate.
 Sodium lauryl sulphate is used in the production of hard gelatin capsules
where it is added to the gelatin solution during the preparation stage.
 Adsorption of magnesium stearate to the powder or granule surfaces also
prevents agglomeration of the feed material and aids flow.

39. II. Suppositories
 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 polyoxyethylene sorbitan
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.
(Corrigan OI, Healy AM. Surfactants in Pharmaceutical Products and Systems.)

40.  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.

41. LIQUID SYSTEMS
Formulation of Solution
Surfactants used in Formulation of Solution as solubilizing agent, which
increase Drug solubility. It includes Sorbitan mono oleate and PEG. It used in
rang 0.05-0.5% to avoid toxicity.[26]
• Formulation of Suspension (Dispersants)
 surfactants may be used in the formulation of suspension to aid dispersion
of the solid particles in the liquid.
 This is particularly important if the powder is not readily wetted by the
liquid vehicle. Surfactants can reduce the interfacial tension between the
solid particles and the liquid vehicle.

42.  The advancing contact angle is reduced, and wetting of the solid
particles promoted. Such a system is said to be deflocculated.
 The inclusion of a surface-active agent to improve powder wettability
can often improve the bioavailability of the formulation.

43. 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, Setchell D.Eur J Prosthodont Restor Dent. 2009

44. 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.
• Recently, solutions of synthetic surfactants have been developed for their
cerumenolytic activity in the removal of ear wax.

45. • One of these agents are tri ethanolamine polypeptide oleate-
condensate, commercially formulated in propylene glycol, is used to
emulsify the cerumen thereby facilitating its removal (Cerumenex
drops).
• Another commercial product utilizes carbamide peroxide in
glycerin/propylene glycol (Debrox drops). On contact with the
cerumen, the carbamide peroxide releases oxygen which disrupts the
integrity of the impacted wax, allowing its easy removal.
Brands in pakistan
ABBOWAX drops, CARBOWAX drops
(Dimmitt P.J Pediatr. Health Care. 2005 Sep-Oct;)

46. SEMISOLID 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).

47. 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)

49. 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.)

50. 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.)

51. Formulation of Aerosols
 Surfactants are found in both solution and suspension formulations of metered
dose inhalers (MDIs).
 The most common surfactants found in pressurized aerosol preparations
include
 sorbitan trioleate (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.

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