United States Patent [191
`Friedman et a].
`
`USOO5744155A
`[11] Patent Number:
`[45] Date of Patent:
`
`5,744,155
`Apr. 28, 1998
`
`3/1992 WLPO
`92103121
`92/13147 10/1992 W0
`93/00076
`l/19‘93 WIPO
`93/00077 “19% W0
`94/0357 7/1993 W0
`Oil-HER PUBLICATIONS
`
`Longer. MA. and LR. Robinson. (1986). Pharmacy Inter
`
`nationaL May ISSUC, PP, Nagai. T. and Y. Machida. (1985). Pharmacy Intemational,
`
`Aug. Issue. pp. 196-200.
`J. Pharm. Parmacol (1992). 44 (Suppl. 1): 186-190.
`Pa
`0!
`Primary Examiner-Raj Bawa
`57
`ABSTRACT
`[
`1
`The invention relates to an oil-in-water emulsion and related
`method for administration of a drug to a mucosal surface.
`The emulsion has an aqueous continuous phase and a
`plurality of submicron particles having an average particle
`diameter of from 10 nm to 600 nm. with the particles having
`a hydrophobic core of a fat or oil which is surrounded by a
`surfactant layer. The emulsion further includes a drug and a
`mucoadhcsive polymer which is a Polymer 01. copolymgl. of
`acrylic acid or methacrylic acid. a poly(methyl vinyl ether]
`maleic anhydride) copolymer. pectin. alginic acid. hyalu
`ronic acid. chitosan. gum tragacanth. karaya gum or car
`boxymethylcellulose. The hydrophobic core has less than
`1% (w/w) protein. relative to the weight of the hydrophobic
`_
`_
`core. and the emulsion contains less than 5% (W/w)
`surfactant. relative to the weight of the hydrophobic core.
`
`42 Claims, 7 Drawing Sheets
`
`[54] BIOADHESIVE EMULSION PREPARATIONS
`FOR ENHANCED DRUG DELIVERY
`
`[76] Inventors: Doron Friedman. 33 Alon. Carmei
`Yosef; Joseph Schwartz. 40 Benjamin
`Street; Shimon Amselem. 38 Benjamin.
`both of Rehovot. all of Israel
`
`21 A L N .2 [ 1 pp 0
`
`
`
`[22] Filed:
`
`
`
`’2
`Aug. 13, 1993
`
`[56]
`
`
`
`a
`[5 [52] US. Cl. ........................ .. 424/434; 424/435; 424/436; ................................................... u
`
`424/450; 514/937; 514/938
`[5 8] Field of Search ................................... .. 424/434. 435.
`424/436. 450. 484; 514/937. 938
`'
`References Clted
`,TENT Cm {EN-I.
`US P
`D0
`S
`4,548,922 10/1985 Carey et a1. .............................. .. 514/4
`5,055,303 10/1991 Riley, Jr- --- -
`424/436
`5,120,710
`6/1992 hedtke
`----- -- 514/3
`5,188,837
`211993 Dumb m; ................................ .. 424/450
`FOREIGN PATENT DOCUMENTS
`
`0 “5 627 12/1983 Ema" Pat Om -
`g :22
`gum” 2a"
`'
`'
`0 494 654 111992 Emma“ at‘
`'
`uropean Pat. Off. .
`2 127 689 8/1983 United Kingdom _
`90/0316‘;
`4/1990 wlpo _
`91/05545
`5/l99l WIPO .
`91/14454 10/1991 WIPO .
`
`E40
`
`220
`
`200
`
`180
`
`g 160 m
`
`g 140 l’
`E
`1;, 120
`g 100
`
`‘5
`5
`
`an -
`_
`
`6n —
`
`40 —
`
`20 —
`
`O
`
`1
`
`0
`
`1
`
`I
`30
`
`I
`so
`
`t
`90
`
`I
`
`I
`
`i
`120
`
`I
`150
`
`Y
`
`1
`180
`
`r
`
`Time lrmnutesl
`+ BOUIU sahne IC
`—-n-— EOIU 5811118 IV
`——<>— EODlU SHE-H IE
`
`1
`
`

`
`US. Patent
`
`Apr. 28, 1998
`
`Sheet 1 0f 1
`
`5,744,155
`
`Polymer Arrangement in 6 Gel Matrix
`
`FIG. 1A
`
`FIG. 1B
`
`A Polymer
`II Cross Link
`
`Emulsion 011 Droplets
`
`0i 1 Droplet.
`
`2
`
`

`
`US. Patent
`
`Apr. 28, 1998
`
`Sheet 2 of 7
`
`5,744,155
`
`Emulsion 011 Droplets in a Gel Matrix
`
`Bioadhesive. Polymer Coated O11 Droplets
`
`FIG.
`
`1D
`
`3
`
`

`
`US. Patent
`
`Apr. 28, 1998
`
`Sheet 3 of 7
`
`5,744,155
`
`CQSUESE
`cossn?bm?u
`coSZommG
`
`$955
`H6235
`Lmerom
`5550a
`69:25
`826
`c2225 E In
`
`m.m
`
`m .QE
`
`4
`
`

`
`US. Patent
`
`Apr. 28, 1998
`
`Sheet 4 of 7
`
`5,744,155
`
`8.0
`
`6
`AE
`
`_ 5
`
`.5 $3506 296
`
`0 5
`
`5
`
`_
`
`0.0
`
`1.0
`
`2.0
`Time (hours)
`
`3.0
`
`4 .0
`
`— P < 0.05
`l§| Diameter w! Lh SME IAUC=4 .9]
`D Diameter for SME/Car‘bolAUC
`
`FIG. 3
`
`5
`
`

`
`US. Patent
`
`Apr. 28, 1998
`
`Sheet 5 of 7
`
`5,744,155
`
`A 4000
`
`c
`
`E 3500-
`><
`
`a: 3000-
`“‘
`“g 2500-
`:3
`
`>< 2000-
`g
`:3 1500-
`g’
`3 1000-
`g
`B 500-
`5
`<
`
`0
`
`0
`
`160
`
`"
`
`- 140
`- 130
`
`- 120 _
`~ 110 f}
`- 100 g
`- 90 E
`
`- 80 Q
`- 70 j‘;
`- 60 l3
`' 50 SJ
`~ 40 E
`- 30
`- 20
`~ 10
`0
`120
`
`.
`
`I
`20
`
`.
`40
`
`I
`60
`
`-
`80
`
`-
`100
`
`LMWH dose IU
`
`—-—I—— Maxma] Ef fect [ME'/.)
`--~*-- AUC lsec” min)
`
`FIG. 4
`
`6
`
`

`
`US. Patent
`
`Apr. 23, 1998
`
`Sheet 6 of 7
`
`5,744,155
`
`
`
`Blood clotting time (seconds)
`
`
`
`
`
`240 -—
`
`2E0
`
`200
`
`180
`
`160
`
`140
`
`120
`
`100
`
`80—
`
`60
`
`4D
`
`20-—
`
`O
`
`I
`
`O
`
`I
`
`|
`30
`
`|
`
`|
`B0
`
`l
`
`|
`90
`
`I
`120
`
`I
`150
`
`I
`180
`
`Time (minutes)
`—{§—— 300IU saline IC
`_n— 5OIU saline IV
`—<>— EOOIU SME-H IC
`
`FIG. 5
`
`7
`
`

`
`U.S. Patent
`
`Apr. 23, 1993
`
`Sheet 7 of 7
`
`5,744,155
`
`
`
` I.C.300IU.Sa]1ne
`
`I.C.200IU,SME-P
`
`Mean Blood Clotting Time (seconds)
`
`FIG. 6
`
`8
`
`

`
`5 .744, 155
`
`1
`BIOADHESIVE EMULSION PREPARATIONS
`FOR ENHANCED DRUG DELIVERY
`
`1. FIELD OF THE INVENTION
`
`The present invention relates to bioadhesive emulsions
`useful as pharmaceutical compositions for enhanced drug
`delivery into or through bodily mucous membranes. such as
`corneal. conjunctival. buccal. sublingual. nasal. pulmonary.
`stomachic. intestinal. rectal. uterine. bladder and vaginal
`mucosa.
`
`2. BACKGROUND OF THE INVENTION
`
`2
`for bioadhesion testing involves interaction of the drug
`delivery system under investigation with ocular surfaces
`such as conjunctiva or cornea. A new ocular formulation of
`the beta-blocker betaxolol. “Betoptic S.” contains the drug
`absorbed on micropowdered cation exchange resin sus
`pended in aqueous solution with Carbopol. Carbopol in this
`formulation is a suspending and viscosity regulating agent.
`Corneal retention of Carbopol coated phosphatidylcholine
`liposomes is signi?cantly greater compared with uncoated
`liposomes. especially at pH 5.0. In a model study. the miotic
`agent tropicamide was employed in a liposomal formulation;
`Davies et al.. J. Pharm. Res. (1992) 921137-1144. The
`pH-dependent lecithin-polyacrylic binding. followed by
`complex formation. was described for three liposome prepa
`rations. It was found that every phosphatidylcholine vesicle
`was coated with a swollen gel layer. and the mean particle
`size increased from 260 to 1300 nm. Such modi?cation
`decreased the rate of drug release from liposomes and
`increased retention time of liposomes in the eye. but no
`signi?cant differences were found in activity and bioavail
`ability between the drug in solution and in Carbopol-coated
`liposomes.
`In EPA 0028110. polyacrylic acid derivatives are claimed
`as stabilizers for pharmaceutical emulsions. Carbopol in
`such compositions. at concentrations near the gel-point and
`at neutral pH. stabilizes the emulsion. Final preparations
`exhibited a viscosity of 66-132 eentipoise. and could be
`autoclaved. Bioadhesive properties were not reported and
`would not be expected. since in all examples the emulsions
`were adjusted to pH 7. at which mucosal binding is
`Zerbe et al.. WO 93/00076. disclose a drug delivery
`system of microparticles having a spherical core composed
`of a biopolymer. preferably a protein such as albumin or
`gelatin. which typically has been crosslinked or denatured to
`maintain its structural coherency. The spherical core is
`suggested to be combined with a bioadhesive polymer.
`Riley. US. Pat. No. 5.055.303. discloses a bioadherent
`emulsion of the water~in-hydrophobic phase type wherein
`the continuous hydrophobic phase is a solid fat. Bioadhesion
`is not attributed to a speci?c adherent component. but rather
`is apparently ascribable to the viscosity of the solid con
`tinuous phase.
`3. SUMIvIARY OF THE INVENTION
`The present invention provides novel compositions and
`methods for enhancing bioadhesive properties of lipid-in
`water type emulsions containing drugs or other biologically
`active compounds.
`The emulsion comprises a colloidal dispersion of droplets
`or particles having a hydrophobic core and containing a
`bioadhesive. preferably mucoadhesive. macromolecule. In
`preferred embodiments. the emulsion contains a biologically
`active agent. which may be distributed between the hydro
`phobic and aqueous phases of an oil-in-water type emulsion.
`or may be present predominately in one of the phases. In
`certain embodiments the emulsion is stabilized with
`amphiphilic and/or non-ionic surfactants.
`The present emulsions are adapted for application to a
`mucosal surface of a vertebrate animal. preferably a
`mammal. including humans. These compositions improve
`the permeability and bioavailability of active compounds
`after application to a mucous surface. Mucosal surfaces of
`interest include the corneal. conjunctival. nasal. buccal.
`sublingual. pulmonary. stomachic. intestinal. uteral. bladder.
`rectal and vaginal mucosa.
`
`4. BRIEF DESCRIPTION OF THE FIGURES
`FIG. 1 illustrates some of the differences among a cross
`linked polymer gel matrix (A). a conventional oil-in-water
`
`20
`
`25
`
`30
`
`35
`
`Bioadhesion is the characteristic of certain natural and
`synthetic polymers of binding to various biological tissues.
`Of particular interest are polymers which bind to the mucous
`lining that covers the surface of many tissues which com
`municate directly or indirectly with the external
`environment. such as the gut. respiratory tract. reproductive
`organs. and cornea. Mucus binding polymers may be
`referred to as mucoadhesive.
`Several bioadhesive. and speci?cally mucoadhesive.
`polymers are known. The chemical properties of the main
`mucoadhesive polymers are summarized as follows:
`a. strong H-bonding groups (—OH. —COOH) in rela
`tively high concentration;
`b. strong anionic charges;
`c. sui‘?cient ?exibility of polymer backbone to penetrate
`the mucus network or tissue crevices;
`d. surface tension characteristics suitable for wetting
`mucus and mucosal tissue surfaces; and
`e. high molecular weight.
`Bioadhesive polymers currently used in pharmaceutical
`preparations include: carboxymethylcellulose (CMC).
`hydroxypropylmethylcellulose (HPMC). polyacrylic and
`polymethaerylic acid and their derivatives. pectin. alginic
`acid. chitosan. polyvinylpyrrolidone. hyaluronic acid. and
`polyvinyl alcohol. The most frequently used polymer is
`Carbopol (Carbomer). which is a high molecular weight
`polyacrylic acid polymer. It is used in many formulations for
`bioadhesive drug delivery systems, as a suspending agent. as
`a tablet coating. and in ocular suspensions.
`Carbopol forms thixotropic mixtures with water at pH
`above 6.5 and at concentrations as low as 0.25-0.3% in
`45
`water. The gel-forming properties of Carbopol strongly
`depend on salt concentration and ionic strength of the
`formulation. The drug delivery enhancing effect of Carbopol
`on coated tablets may be due to both the polymer-mucus
`interaction and the prolongation of residence time due to
`increased viscosity.
`Many workers have investigated the effect of pH on the
`interaction of polyacrylic acid with mucus. noting that the
`adhesion of acrylic-based polymers to mucous membrane is
`greater at pH <6. Protonation of the carboxyl groups (pKa
`4.75) permits H-bonding between the polymer and the
`mucin network. resulting in enhanced retention of the poly
`mer in contact with a mucosal surface.
`Several reports of liposome suspensions containing bio
`adhesive polymers have been published recently. Interaction
`between mucoadhesive polymers and phospholipid vesicles
`has. in turn. resulted in the prolonged corneal residence of
`those vesicles.
`The biological effects of incorporating bioadhesive poly
`mers into drug formulations can be tested by various
`methods. such as increased retention time while in the eye
`or increased effective drug concentration. One of the models
`
`50
`
`55
`
`65
`
`9
`
`

`
`5,744,155
`
`3
`emulsion (B). an emulsion of oil droplets di?‘using in a gel
`matrix (C). and bioadhesive coated emulsion particles of an
`aspect of the present invention (D).
`FIG. 2 is a ?owchart showing pH changes during the
`preparation of an exemplary bioadhesive emulsion wherein
`Carbopol is the bioadhesive polymer.
`FIG. 3 is a graph showing the change in pupil diameter
`versus time after intraocular administration of the p?o
`carpine emulsion of Example 13.
`FIG. 4 shows the approximately linear dose-response of
`blood clotting time and maximal effect. ME %. versus dose
`of i.v. treatment with low molecular weight heparin
`(LMWH). for groups A-C of Example 27.
`FIG. 5 is a pro?le of blood clotting time over post
`n'eatment time after colonic administration of LMWH in
`saline versus SME and versus i.v. treated rats. for groups B.
`E. and G.
`FIG. 6 shows the blood clotting time at Tm (90 minutes)
`for the indicated routes of administration and vehicles used
`to deliver the LMWH.
`
`20
`
`5. DETAILED DESCRIPTION OF THE
`INVENTION
`Use of bioadhesive polymers in pharmaceutical emul
`sions affords enhanced delivery of drugs in bioadhesive
`polymer-coated suspensions. Bioadhesive pharmaceutical
`emulsions: a) prolong the residence time in situ. thereby
`decreasing the number of drug administrations required per
`day; and b) may be localized in the speci?ed region to
`improve and enhance targeting and bioavailability of deliv
`ered drugs.
`The ability to retain and localize a drug delivery emulsion
`in a selected region leads to improved bioavailability. espe
`cially for drugs exhibiting a narrow window of adsorption
`due to rapid metabolic turnover or quick excretion. Intimate
`contact with the target absorption membrane improves both
`the extent and rate of drug absorption.
`
`25
`
`30
`
`35
`
`4
`factants selected from the group consisting of an unhaloge
`nated aliphatic C3-C6 alcohol. a free fatty acid. a mono- or
`di-glyceride. a polyglycerol fatty acid ester (e.g.. Plurol). or
`a lysophosphatidyl choline. One or all of the above-named
`cosurfactants may comprise less than 5%. commonly less
`than 1%. and frequently less than 0.1% (w/w) relative to the
`weight of the hydrophobic core.
`The emulsion further comprises a bioadhesive. usually
`rnucoadhesive. polymer. The polymer frequently may con
`tain multiple carboxylic acid moieties. e.g.. polyacrylates.
`alginic acid. hyaluronic acid. pectin. or carboxymethylcel
`lulose. Polymers bearing polyarnine groups also are capable
`of binding to mucin. e.g.. chitosan. Certain mucin-binding
`polymers are uncharged. e.g.. hydroxypropylmethyl cellu
`lose.
`In many cases. the bioadhesive polymer is believed to
`coat or form a layer on the outer surface of the particle core.
`possibly in association with the surfactant. Frequently the
`addition of the bioadhesive polymer increases the mean
`particle diameter of the emulsion. as may be seen. e.g.. in
`Examples 3. 8-9. and 13. This result is consistent with the
`“coating” model of polymer-core interaction. since the
`added polymer layer would be expected to result in a greater
`diameter. However. in other cases the added polymer makes
`little difference in. or actually decreases. particle diameter;
`see. e.g.. Examples 4-5. 6-7. 17. and 21. In these
`circumstances. the polymer may have surfactant as well as
`mucous-binding properties. thereby inserting itself deeply
`into the surfactant interface. In extreme cases. the polymer
`may be su?iciently surface-active to reduce the average
`hydrophobic core diameter by increasing the effective
`surfactant-to-lipid ratio.
`Regardless of the detailed molecular structure of the
`polymer-particle association. emulsions combining hydro
`phobic core and bioadhesive polymer are Within the scope of
`the invention.
`The continuous phase of the emulsion is aqueous. and
`may contain salts. sugars. antioxidants. preservatives.
`microbicides. buffers. osmoticants. cryoprotectants. and
`other pharrnaceutically useful additives or solutes.
`The emulsion also contains a biologically active
`compound. usually a drug. most commonly a prescription
`drug. although vitamins and other nonprescription medica
`tions also may be included. The active compound may be
`either hydrophilic or hydrophobic. since the emulsion pro
`vides a biphasic microenvironment.
`
`5.1. Features of the Emulsion Particles
`The bioadhesive emulsions of the present invention com
`prise an aqueous continuous phase suspending a colloidal
`phase of submicron particles. The particles have a weighted
`average diameter of 10 to 600 run. more preferably 30 to 500
`nm. most preferably 70 to 300 nm. In many embodiments.
`the weighted average diameter will be less than 450 nm. 400
`nm. 300 nm. or 200 nm. Usually the diameter will be greater
`than 40 nm or 50 nm. and frequently is greater than 70 nm.
`Often the above-stated upper and lower diameter ranges will
`include both the weighted average and at least one standard
`deviation of particle diameter.
`The emulsion particle comprises a hydrophobic core.
`often including or even consisting essentially of triglyceride.
`Optionally other hydrophobic lipids may be used. including
`cholesterol or cholesteryl esters. parat?n. mineral oil. sili
`cone oil. and waxes. Usually the core of the particles will be
`substantially free of protein. i.e.. less than 1% (w/w). and in
`most cases less than 0.1% protein.
`The emulsion usually further comprises at least one
`surfactant. which may be a natural biologically compatible
`surfactant such as phospholipid (e.g.. lecithin) or a pharma
`oeutically acceptable nonnatural surfactant such as Tween
`80. The surfactant assists in maintaining particles within the
`desired size range and preventing their aggregation.
`In many embodiments the emulsion may be formed and
`stabilized in the substantial absence of one or more cosur
`
`45
`
`5.2. Composition of the Hydrophobic Core
`A hydrophobic compound which is suitably nontoxic for
`administration to mucosal surfaces may be used as a com
`ponent of the core. Examples include triglycerides. prefer
`ably of food grade purity or better. which may be produced
`by synthesis or by isolation from natural sources. Natural
`sources may include animal fat or vegetable oil. e.g.. soy oil.
`a source of long chain triglycerides (LCl‘). Other triglycer
`ides of interest are composed predominantly of medium
`length fatty acids (CID-C18). denoted medium chain trig
`lycerides (MCI‘). The fatty acid moieties of such triglycer
`ides may be unsaturated. monounsaturated or polyunsatu
`rated; mixtures of triglycerides having various fatty acid
`moieties are acceptable. The core may comprise a single
`hydrophobic compound or a mixture of compounds.
`Other hydrophobic compounds which may be used
`include silicone oil. mineral oil. para?in. and aliphatic and
`aromatic esters of hydrophobic acids. e.g.. isopropyl
`myristate. benzyl benzoate. and tocopherol acetate. The
`
`55
`
`65
`
`10
`
`

`
`5,744,155
`
`5
`ester category includes waxes. which often are composed of
`fatty acid moieties esteri?ed with aliphatic alcohols. includ
`ing C2-C6 short chain alcohols and Cit-C22 fatty alcohols.
`Optionally the core may contain cholesterol or cholesteryl
`esters. In many embodiments. cholesteryl esters or choles
`terol comprise less than 10%. 5%. 1%. or even 0.1% (w/w)
`of the total hydrophobic components of the core.
`Considerations in choice of core material include low
`toxicity and irritancy. biocompatibility. stability. and high
`loading capacity for biologically active compounds of inter
`est such as drugs. Preferred hydrophobic core components
`have molecular weights below about 5.000 Da. more pref
`erably below about 2.000 Da. and most preferably below
`about 1.500 Da. An exception is provided by silicone oils.
`which remain useful at much higher molecular weights.
`
`5.3. Composition of Surfactant Component
`Some embodiments of the invention provide an improved
`bioadhesive emulsion comprising incorporation of an
`amphiphilic and/or nonionic surfactant such as
`phosphatidylcholine. Tween. etc. The surfactant is believed
`in many embodiments to interact with the bioadhesive
`polymer to form a hydrated polymer ?lm coating associated
`with the surfactant at the stabilized lipid/water interface
`surrounding the particle core.
`Preferred compositions contain a surfactant component.
`The surfactant stabilizes the outer surface of the hydropho
`bic core component of the emulsion particles. thereby pro
`moting a more uniform and manipulable particle size. Usu
`ally the surfactant is present in a proportion of 0.01% to 5%
`(w/w) of the emulsion. preferably 0.05% to 2%.
`‘Typically. the weight percentage of surfactant relative to
`hydrophobic (oil or other lipid) component is from 0.2% to
`50%. more preferably from 5% to 20%. Higher ratios of
`surfactant to core lipid tend to promote smaller particle core
`diameters.
`Surfactants may be either natural compounds. such as
`phospholipids and cholates. or nonnatural compounds such
`as: polysorbates. which are fatty acid esters of polyethoxy
`lated sorbitol (Tween); polyethylene glycol esters of fatty
`acids from sources such as castor oil (Emulfor); polyethoxy
`lated fatty acid. e.g. stearic acid (Simulsol M-53); Nonidet;
`polyethoxylated isooctylphenol/formaldehyde polymer
`(Tyloxapol); poloxamers. e.g.. poly(oxyethylene)poly
`(oxypropylene) block copolymers (Pluronic); polyoxyethyl
`ene fatty alcohol ethers (Brij); polyoxyethylene nonylpheuyl
`ethers (Triton N); polyoxyethylene isooctylphenyl ethers
`(Triton X); and SDS. Mixtures of surfactant molecules.
`including mixtures of surfactants of di?m'ent chemical
`types. are acceptable. Surfactants should be suitable for
`pharmaceutical administration and compatible with the drug
`to be delivered.
`Particularly suitable surfactants include phospholipids.
`which are highly biocompatible. Especially preferred phos
`pholipids are phosphatidylcholines (lecithins). such as soy
`or egg lecithin. Other suitable phospholipids include
`phosphatidylglycerol. phosphatidylinositol.
`phosphatidylserine. phosphatidic acid. cardiolipin. and
`phosphatidylethanolamine. The phospholipids may be iso
`lated from natural sources or prepared by synthesis. Phos
`pholipid surfactants are believed usually to form a single
`monolayer coating of the hydrophobic core.
`In certain embodiments. the emulsion may be limited in
`or substantially free of one or more cosurfactants selected
`from the group consisting of free fatty acids. mono- or
`di-glycerides (fatty acid mono- or diesters of glycerol).
`
`6
`aliphatic C3-C6 monoalcohols (exclusive of. e.g.. chlorobu
`tanol or other haloalkyl alcohol preservative). polyglycerol
`fatty acid esters (Plurol). or lysophosphatidyl choline. In
`many embodiments. the particular limited cosurfactant from
`the above group may constitute less than 5%. usually less
`than 1%. often less than 0.1%. relative to the weight of
`hydrophobic core component. In some embodiments. one or
`more cosurfactants may be present.
`
`10
`
`20
`
`25
`
`35
`
`45
`
`5.4. Bioactive Component
`The pharmacological activity of a wide variety of drugs
`render them suitable for use in bioadhesive emulsion
`formulations. to treat a number of conditions. In general.
`those drugs suitable for topical application to external and
`internal ocular. vaginal. oral. buccal. nasal. pulmonary. and
`rectal mucous surfaces may be employed. Suitable drugs
`include. inter alia: antivirals (acyclovir. IUdR. ganciclovir.
`vidarabine. AZT). steroidal and non-steroidal anti
`in?ammatory drugs (dexamethasone. loteprednol. predniso
`lone derivatives. diclofenac. indomethacin. piroxicam etc.).
`antibiotics (e.g.. ampicillin and erythromycin) antifungals
`(e.g.. rniconazole). vitamins. hormones. retinoic acid. local
`anesthetics. calcium channel blockers (e.g.. Verapamil).
`prostaglandins and prostacyclins. antineoplastic and antime
`tabolitic drugs. miotics. cholinergics. adrenergic
`antagonists. anticonvulsants (e.g.. phenytoin). antianxiety
`agents. major tranquilizers. antidepressants. anabolic
`steroids. estrogens. progesterones. and glycosaminoglycans
`(heparin. heparan. chondroitin sulfate. and low molecular
`weight derivatives thereof).
`Descriptions of suitable drugs within these therapeutic
`classi?cations may be found in standard reference
`textbooks. such as Goodman and Gilman’s Pharmacologi
`cal Basis of Therapeutics, eighth edition (1990).
`Many of the drugs listed above are poorly soluble in water
`and slowly adsorbed through mucous surfaces. Low bio
`availability of such drugs severely limits their applicability.
`usage and e?ectiveness. Incorporation of such drugs into
`mucoadhesive emulsions of the present invention increases
`their bioavailability. Some exemplary drugs which would
`exhibit improved bioavailability when administered in a
`bioadhesive emulsion of the present invention include
`ampicillin. erythromycin. hydralazine. valproic acid. and
`verapamil.
`
`5.4.1. Protein Components
`In certain preferred preparations. the lipid particles of the
`inventive emulsions do not incorporate milk fat globule
`apolipoproteins or serum apolipoproteins such as apoB.
`apoAI. apoAlI. or apoE. Lipid particles of the invention in
`certain preferred embodiments also are substantially free of
`intracellular marker proteins associated with the intracellu
`lar cytoskeleton (e.g.. actin. myosin. troponin. tubulin.
`virnentin. and spectrin). Lipid particles which do not contain
`intracellular marker proteins are herein de?ned as “noncel
`lular” particles. since they lack characteristic indicia of lipid
`particles present in or derived from cellular sources.
`In most embodiments. the emulsion particles will be free
`or substantially free of the above or other proteins. i.e.. less
`than 5%. usually less than 1%. and frequently less than 0.1%
`(MW) protein relative to other particle components.
`
`65
`
`5.5. Bioadhesive Macromolecules
`
`Emulsions of the present invention contain a bioadhesive
`macromolecule or polymer in an amount su?icient to confer
`
`11
`
`

`
`5,744,155
`
`8
`Incorporation of the bioadhesive macromolecule into the
`emulsion is believed to result in spontaneous association of
`the macromolecule with. and coating of. the emulsion
`particles. as in represented diagrammatically in FIG. 1.
`However. the resulting emulsion is within the scope of the
`invention regardless of the details of the microscopic par
`ticle structure.
`
`10
`
`15
`
`20
`
`25
`
`30
`
`5.6. Aqueous Solution
`
`The aqueous solution constituting the continuous phase
`usually contains a biologically compatible bu?er. Since
`bioadhesion of polymers having acidic groups is more
`pronounced at lower pH. the bulfer is usually adjusted to the
`pH range 3-7. usually pH 3.5-6.5. more usually pH 4 to 6.
`frequently pH 4.5 to 5.5. Certain basic polymers having
`amine groups. such as chitosan. may be exposed to pH as
`low as 3 during preparation at the emulsion. although the
`usual pH range as administered is similar to or may be
`slightly higher than that for acidic polymers. i.e.. pH 6-8.
`Optionally. suitable chelating agents such as citric acid or
`EDTA may be present to minimize polyvalent or divalent
`cation binding to the acidic groups of the polymer. Other
`optional components may include. inter alia. antioxidants.
`antimicrobials. cryoprotectants. preservatives. salts. amino
`acids. and additives such as glycerol to adjust the solution
`tonicity.
`In many embodiments. the aqueous solution is substan
`tially free from sorbitol; i.e.. the weight of sorbitol in the
`emulsion may be less than 10% (w/w) relative to the weight
`of hydrophobic core lipid. often less than 5%. commonly
`less than 1% or even 0.1%. and may be essentially absent.
`In many embodiments. the emulsion is also substantially
`free from phosphorylcholine. which. like sorbitol. may be
`limited to levels of 10%. 5%. 1%. or 0.1% (w/w) or less.
`
`7
`bioadhesive properties. The bioadhesive macromolecule
`enhances the delivery of biologically active agents on or
`through the target surface. The bioadhesive macromolecule
`may be selected from acidic nonnaturally occurring
`polymers. preferably having at least one acidic group per
`four repeating or monomeric subunit moieties. such as
`poly(acrylic)- and/or poly(methacrylic) acid (e.g.. Carbopol.
`Carbomer). poly(methylvinyl ether/maleic anhydride)
`copolymer. and their mixtures and copolymers; acidic syn
`thetically modi?ed natural polymers. such as carboxymeth
`ylcellulose (CMC); neutral synthetically modi?ed natural
`polymers. such as (hydroxypropyl)methylcellulose; basic
`amine-bearing polymers such as chitosan; acidic polymers
`obtainable from natural sources. such as alginic acid. hyalu
`ronic acid. pectin. gum tragacanth. and karaya gum; and
`neutral nonnaturally occurring polymers. such as polyviny
`lalcohol; or their mixtures. The ionizable polymers may be
`present as free acids. bases. or salts. usually in a ?nal
`concentration of 0.01-0.5% (w/vol).
`Bioadhesive macromolecules often form viscous
`solutions. in addition to possessing more specific mucin
`binding properties. These e?ects may be distinguished by
`comparing the degree of adhesion to a mucin surface of a
`solution prepared with the putative bioadhesive macromol
`ecule versus a similar control emulsion prepared with a
`non-bioadhesive macromolecule of comparable viscosity:
`for example. a starch or dextran solution. At similar
`viscosities. the emulsion prepared with a bioadhesive mac
`romolecule will bind to the mucin surface more strongly
`than will the control emulsion prepared with the “nonbind
`ing" macromolecule such as starch. Preferably. the bioad
`hesive macromolecule will produce at least 25% greater
`mucin binding than the control emulsion. more preferably at
`least 50% greater. still more preferably at least 100% greater
`mucin binding than the control emulsion. Either binding to
`mucin per se or amount or biological effect of the drug
`delivered may be used as a measurement parameter for
`bioadhesion. This test may be used to distinguish preferred
`bioadhesive molecules.
`As used herein. a polymer of an indicated monomeric
`subunit contains at least 75%. preferably at least 90%. and
`up to 100% of the indicated type of monomer subunit; a
`copolymer of an indicated type of monomeric subunit con
`tains at least 10%. preferably at least 25% of that monomeric
`subunit.
`A preferred bioadhesive macromolecule is the family of
`acrylic acid polymers and copolymers. (e.g..
`CARBOPOLTM). These contain the general structure:
`
`35
`
`45
`
`5.7. Dehydrated Emulsions
`
`A further aspect of the invention provides dehydrated
`emulsions. made by dehydrating a bioadhesive emulsion of
`the type described herein. Dehydrated emulsions may be
`stored for prolonged periods with minimal degradation. then
`reconstituted with water shortly before use. Residual water
`content in the dehydrated emulsion is usually less than 5%
`(w/w). commonly less than 2%. and often less than 1%.
`Dehydration may be performed by standard methods.
`such as drying under reduced pressure; when the emulsion
`is frozen prior to dehydration. this low pressure evaporation
`is known as lyophilization. Freezing may be performed
`conveniently in a dry ice-acetone or ethyl alcohol bath. The
`pressure reduction may be achieved conveniently with a
`mechanical vacuum pump. usually ?tted with a liquid nitro
`gen cold trap to protect the pump from contamination.
`Pressures in the low millitorr range. e.g.. 10-50 millitorr. are
`routinely achievable. but higher or lower pressures are
`su?icient.
`A cryoprotectant or anticoalescent compound may be
`added to the emulsion prior to dehydration to inhibit ?oc
`culation and coalescence upon rehydration. The cryopro
`tectant may be of any type known in the art. including sugars
`and polysaccharides such as sucrose or trehalose. and non
`natural polymers such as polyvinylpyrrolidone. Cryopro
`tectants are usually present at less than 25%. commonly
`10%. more commonly 5%. 4% (w/v) or less in the emulsion
`before lyophilization.
`A preferred category of cryoprotectants is amino acids
`and oligopeptides. Preferred amino acids include valine.
`
`One preferred group of polymers of acrylic acid is commer
`cially available under the tradename Carbopol. Carbopol
`934 is available in a pharmaceutical grade. ‘
`Preferred bioadhesive or mucoadhesive macromolecules
`have a molecular weight of at least 50 kDa. preferably at
`least 300 kDa. and most preferably at least 1.000 kDa.
`Favored polymeric ionizable macromolecules have not less
`than 2 mole percent acidic groups (e.g.. COOH. S0311) or
`basic groups (NR2. NRH. NR2). relative to the number of
`monomeric units. More preferably. the acidic or basic
`groups constitute at least 5 mole percent. more preferably 10
`mole percent. and still more preferably at least 25 or even
`50. up to 100 mole % relative to the number of monomeric
`units of the macromolecule.
`Preferred macromolecules also are soluble in water
`throughout their relevant concentration range (0.0l—0.5%
`w/vol).
`
`55
`
`65
`
`12
`
`

`
`5,744,155
`
`leucine. isoleucine. lysine. methionine. threonine. serine.
`arginine. alanine. glycine. histidine, proline. phenylalanine.
`taurine. an