EMULSIONS.doc

8/12/2019 EMULSIONS.doc

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An emulsion is liquid preparation containing two immiscible liquids, one ofwhich is dispersed as globules (dispersed phase = internal phase) in the otherliquid (continuous phase = external phase).

Microemulsion: Droplets si e range !.!" to !." m Macroemulsion: Droplets si e range approximatel# $ m.

General Types of Pharmaceutical Emulsions:

") %otions&)%iniments ') reams

) *intments$) +itamin drops

Primary and secondary emulsion:

rimar# emulsion containing one internal phase, for example, oil-in-water emulsion (o w) and water-in-oil emulsion (w o).

/econdar# emulsion= multiple-emulsion: it contains two internal phase, for instance, o w o or w o w. 0t can be used to dela# release orto increase the stabilit# of the acti1e compounds.

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Dispersed phase

ontinuous phase

2o stabili e thesedroplets, emulsif#ingagent should be added

W/O/WO/W/O

O/W

*il

3ater

O/W

*il

O/W

*il

3ater

*il

W/O

3ater *il

W/OW/O

3ater

*il

3ater 3ater

3ater

*il*il

3ater

*il*il


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Emulsion Type and Means of Detection : using of na4ed e#e, it is 1er#difficult to differentiate between o w or w o emulsions. 2hus, the fourfollowing methods ha1e been used to identif# the t#pe if emulsions.

1) Dilution Test: based on the solubilit# of external phase of emulsion.

- o w emulsion can be diluted with water.- w o emulsion can be diluted with oil.

&)Conducti ity Test: water is good conductor of electricit# whereas oil isnon-conductor. 2herefore, continuous phase of water runs electricit# morethan continuous phase of oil.

') Dye!"olu#ility Test:

- 3ater-soluble d#e will dissol1e in the aqueous phase.- *il-soluble d#e will dissol1e in the oil phase.

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5lectrode

6ulb

5mulsion

= 6ulb glows with * 3= 6ulb doesn7t glow with 3 *

8ew dropsof emulsion

8ew dropsof water 3ater distribute

uniforml#

3ater separateout as la#er

* 3 emulsion

3 * emulsion


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$!%luorescence test: oils gi1e fluorescence under 9+ light, while waterdoesn7t. 2herefore, * 3 emulsion shows spott# pattern while 3 * emulsionfluoresces.

". 2o mas4 the taste&. * 3 is con1enient means of orall# administration of water-insoluble

liquids

'. * 3 emulsion facilitates the absorption of water-insolublecompounds comparing to their oil# solution preparations (e.g.1itamins)

. *il-soluble drugs can be gi1en parentrall# in form of oil-in wateremulsion. (e.g 2axol)

$. 5mulsion can be used for external application in cosmetic andtherapeutic uses.

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*il-soluble d#e (e.g. /carlet) 3ater-soluble d#e (e.g. Amaranth d#e)

* 3 3 ** 33 *

3hat is loo4 li4e under the microscope after mixing with suitable d#e

harmaceutical applications of emulsions:


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Theories of Emulsification:

0ncase of two immiscible liquids

An explanation of this phenomenon is because of cohesi1e force between the molecules of each separate liquid exceeds adhesi1e force between two liquids. 2his is manifested as interfacial energ# ortension at boundar# between the liquids.

2herefore, to pre1ent the coalescence and separation, emulsif#ingagents ha1e been used.

2#pes of emulsif#ing agents :

". /urface acti1e agent: adsorbed at oil water interface to formmonomolecular film to reduce the interfacial tension

*il*il

3ater 3ater

*il

3ater

Agitation

/eparate rapidl# into twoclear defined la#ers

*il*il

3ater 3ater

*il

3ater

Agitation

/eparate rapidl# into twoclear defined la#ers

/#stem tends to separate intwo la#er to reduce the surface area

/mall droplet /urface area 0nterfacial tension

/#stem is thermod#namicall#unstable : high energ#;

/#stem tends to separate intwo la#er to reduce the surface area

/mall droplet /urface area 0nterfacial tension


/mall droplet /urface area 0nterfacial tension/mall droplet /urface area 0nterfacial tension



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&.


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ii. 8orm coherent monola#er to pre1ent the coalescence of twodroplet when the# approach each other

iii. ro1ide surface charge which cause repulsion between ad>ust particles

ombination of surface-acti1e agents is used most frequentl#. 2hecombination should form film that closel# pac4ed and condensed

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2his figures shows schematic of oil droplets in an oil-water emulsion. @ou can see the orientation of a2ween and a /pan molecule at the interface

8igure (a) shows good combination, which formsexcellent emulsion.

8igure (b) and (c) show poor emulsion due to lac4 ofclosel# pac4ed or lac4 of complexation, respecti1el#.


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lassification of surface-acti1e agents:

Bote that: Anionic /AA are mainl# used for external used. ationic /AA are used for external used. 2he# ha1e, also, good

antimicrobial acti1it# (e.g. 6en al4onium chloride)

Bonionic /AA are stable o1er wide range of p


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'!Multimolecular adsorption


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C!"olid particle adsorption

8inel# di1ided solid particles are adsorbed at the surface of emulsiondroplet to stabili e them. 2hose particles are wetted b# both oil andwater (but not dissol1ed) and the concentration of these particles forma particulate film that pre1ent the coalescence.

articles that are wetted preferentiall# b# water from o w emulsion,whereas those wetted more b# oil form w o emulsion

Bote that the# are 1er# rare to use and can affect rheolog# of the final product

/i e of the particle is 1er# important, larger particles can lead tocoalescence

F

8inel# di1ided solids

6entonite


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Other emulsifyin( a(ents

Batural emulsif#ing agents:

". 5gg #ol4: it contains phospholipids and cholesterol. 2he mainwithdraw bac4 is that spoils quic4l#G therefore, it can7t be used inindustr#. 0t is used for extemporaneous preparation.

&. 3ool fat: anh#drous lanolin, it is used to prepare w o emulsion forexternal uses.

'. /tarch: it forms starch mucilage and it is restricted for enemas preparation.

. holesterol: it has stabili ing actionG therefore, another emulsifiershould be included.

o* to control emulsion type durin( formulation+

a. +olume of internal and external phases controls the t#pe of emulsion.2he smaller 1olume will be for the internal phase and the larger1olume will be for external phase. 0n some cases, internal phases can

be more than $!H of the total 1olume (see the following section)

b. Dominance of polar and non-polar characteristic of emulsif#ingagents (relati1e solubilit# of emulsif#ing agent in water and oil).Dominance of polar part results in formation of o w emulsion anddominance of non-polar part results in formation of w o emulsion.

Bote that polar groups are better barriers than non-polarG therefore,o w emulsion can be prepared with more than $! H of oil phase internal phase;.

What the factors that affect the choice of emulsion type+

2he choice of emulsion depends on (")-properties and uses of final products(&)- the other material required to be present.

*il-soluble drug is prepared in o w emulsion due its solubilit# and itstaste can be mas4ed b# adding fla1oring agents

8or intra1enous in>ection i.1.; o w emulsion is the onl# t#pe could be used.

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8or intramuscular in>ection i.m.; both o w and w o t#pes ofemulsion could be used. 3ater-soluble drug can be prepared in w oemulsion to get prolonged action (depot therap#)

2opical application:o /emisolid emulsions are called creams and lotions

Methods for preparation of emulsion:

0n small scales such as in pharmac#-hospital labs, mortar and pestleare the needed equipments.

0n large scale such as in pharmaceutical industr#, different machinesare used:

1, Mixer or mechanical stirring : the emulsion is prepared b#agitation of emulsion ingredient

-, olloid mills

.,

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Oil in water emulsion Water in oil emulsion

8or insoluble drug 8or local effect 5asil# to wash from

s4in Doesn7t ha1e greas#

texture of oil# preparation Acceptable b#

consumer

8or water soluble drug an be use to h#drate the upper

la#er of stratum corneum(moisturi ing cream)

an increase the absorption ofdrug from these formulation

an be used to clean s4in from dirt Bot acceptable b# consumer


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5mulsif#ing Agents:

") arboh#drate Materials:

Acacia, 2ragacanth, Agar, ectin. o w emulsion.

&) rotein /ubstances:

elatin, 5gg #ol4, aesin o w emulsion.

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Methods of Preparation of Emulsions:

") ontinental or Dr# um Method:

I :&:"I Method

parts (1olumes) of oil JAnsel. th ed. page '?FK

& parts of water

" part of gum

Acacia or other o w emulsifier is triturated with oil in a perfectl# dr#3edgwood or porcelain mortar until thoroughl# mixed. lass mortar has toosmooth a surface to produce the proper si e reduction of the internal phase(Do not use glass mortar). After the oil and gum ha1e been mixed, the two

parts of water are then added all at once and the mixture is trituratedimmediatel#.

&) 5nglish or wet um Method:

/ame proportion of oil, water and gum are used as in the continental or dr#gum method but the order of mixing is different. Mucilage of the gum is

prepared b# triturating acacia (or other emulsifier) with water. 2he oil is thenadded slowl# in portions, and the mixture is triturated to emulsif# the oil./hould the mixture become too thic4 during the process, additional waterma# be blended into the mixture before another successi1e portion of oil isadded.

') 6ottle or 8orbes 6ottle Method:

9seful for-

5xtemporaneous preparation of emulsion from 1olatile oils or oleaginous

substance of low 1iscosit#. put powdered acacia in a dr# bottle

Add & parts of oil

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2horoughl# sha4e the mixture in the capped bottle. A 1olume of waterapproximatel# equal to the oil is then added in portions, the mixture beingthoroughl# sha4en after each addition.

2his method is not suitable for 1iscous oils (i.e. high 1iscosit# oil).

"ta#ility of Emulsion:

An emulsion is considered to be ph#sicall# unstable if :

a) 2he internal phase tends to form aggregates of globules.

b) %arge globules or aggregates of globules rise to the top or fall to the bottom of the emulsion to form a concentrated la#er of the internal phase.

c) 0f all or part of the liquid of the internal phase becomes Iunemulsified onthe top or bottom of the emulsion.

/eparation of the internal phase from the external phase is called6 5AE0B of the emulsion. 2his is irre1ersible.

- rotect emulsions against the extremes of cold and heat.

-5mulsions ma# be ad1ersel# affected b# microbial contamination.

els and Magmas:

els are defined as semisolid s#stems consisting of dispersions made up ofeither small inorganic particles or large organic molecules enclosing orinterpenetrated b# a liquid. Magmas or Mil4s are gels consisted of flocculesof small distinct particles. els and Magmas are considered colloids becausethe# contain particles within the range of colloidal dispersions.

5xamples of Magmas L els:

6entonite Magma, B8:

reparation of $H bentonite, a nati1e, colloidal h#drated aluminum silicate,in purified water.

Aluminum


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2his is an aqueous suspension of a gelatinous precipitate composed ofinsoluble aluminum h#droxide and h#drated aluminum oxide, equi1alent toabout H of aluminum oxide.

Mil4 of Magnesia, 9/ :

2his is a preparation containing between and C.$H of Magnesiumh#droxide.

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EMULSIONS.doc