United States Patent (19)
`Burnside et al.
`
`USOO5883103A
`Patent Number:
`11
`(45) Date of Patent:
`
`5,883,103
`*Mar 16, 1999
`
`54) ORALACYCLOVIR DELIVERY
`75 Inventors: Beth A. Burnside, Silver Spring; Carol
`E. Mattes, Gaithersburg; Charlotte M.
`McGuinness, Rockville; Edward M.
`Rudnic, North Potomac, George W.
`Belendiuk, Potomac, all of Md.
`73 Assignee: Shire Laboratories Inc., Rockville,
`Md.
`
`*
`
`Notice:
`
`The terminal 10 months of this patent has
`been disclaimed.
`
`21 Appl. No.: 475,036
`22 Filed:
`Jun. 7, 1995
`51
`Int. Cl. ........................... A61K 9/107; A61K 31/52
`52)
`514/262; 514/938; 514/943
`58 Field of Search ..................................... 514/262,938,
`514/943
`
`
`
`56)
`
`References Cited
`
`U.S. PATENT DOCUMENTS
`
`5,206,219 4/1993 Desai.
`5,447,729 9/1995 Belendulk et al. ..................... 424/490
`OTHER PUBLICATIONS
`Chemical Abstracts AN 1994:253414, Gebhard-hansen et
`al, WO 940528 Mar. 17, 1994.
`Ritschel et al., Improvement of Peroral Absorption of
`Cyclosporine A by Microemulsions, Meth. Find. Exp. Clin. P
`harmacol, 12(2): 127-134, (1990).
`
`Shichiri et al...Increased Intestinal Absorption of Insulin in
`a Micellar Solution, First Dept. of Medicine, Osaka Univ.
`Medical School, pp. 175–183, (1977).
`Ritschel, Microelusions for Improved Peptide Absorption
`from the Gastrointestinal Tract, Meth. Find. Exp. Clin. Phar
`macol., 13(3): 205–220, (1991).
`Kararli et al., Oral Delivery of a Renin Inhibitor Compound
`Using Emulsion Formulations, Pharm. Research, vol. 9, No.
`7, pp. 888-893, (1992).
`Myers, et al., Systemic Bioavailability of Penclomedine
`(NSC-338720) from Oil-in-Water Emulsions Adminis
`trated Intraduodenally to Rats, Int’l. Jnl. Of Pharmaceutics,
`78:217-226, (1992).
`Bhargava et al., Using Microemulsions for Drug Delivery,
`Pharm. Tech. ..., pp. 47-51 (Mar. 1987).
`Sarciaux et al., Using Microemulsion Formulations for Oral
`Drug Delivery of Therapeutic Peptides, Intl. Jnl. Of Phar
`maceutics, 120:127–136, (1995).
`Primary Examiner Keith D. MacMillan
`Attorney, Agent, or Firm Elliot M. Olstein; Raina
`Semionow
`ABSTRACT
`57
`A pharmaceutical preparation for oral acyclovir delivery
`comprising a stable, hydrophobic emulsion comprising con
`tinuous phase of a hydrophobic material Selected from the
`group consisting of a long chain carboxylic acid or ester or
`alcohol thereof dispersed in an aqueous phase or (ii) having
`a hydrophilic discontinuous phase dispersed in a hydropho
`bic phase of a long chain carboxylic acid or alcohol thereof.
`The emulsion with acyclovir is incorporated into a pharma
`ceutical carrier Suitable for oral delivery.
`18 Claims, 15 Drawing Sheets
`
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`
`

`

`U.S. Patent
`
`Mar. 16, 1999
`
`Sheet 1 of 15
`
`5,883,103
`
`<| & Y
`
`v &‘
`
`H
`
`LL
`
`[x]
`3.
`
`Oo
`re}
`fx
`Ge
`eo o.
`+S)
`Qs
`i os
`a aw
`—
`on Uv
`N O-A
`n G
`n & ©8O
`4 oO MW
`aS
`eo 2s
`co
`FSF
`8@e
`Dae
`
` C5
`
`+44 Oo
`
`wo
`
`N
`
`o
`
`oO
`
`N
`
`°
`
`Yo
`
`”
`
`o
`
`oO
`
`°
`
`To)
`
`Oo
`
`Specific Activity (dpm)
`
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`

`

`U.S. Patent
`
`Mar 16, 1999
`
`Sheet 2 of 15
`
`5,883,103
`
`N ZOri Vax
`
`
`
`y
`
`Nun 0é Linoleic
`
`n TWeen 20
`
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`

`U.S. Patent
`
`Mar 16, 1999
`
`Sheet 3 of 15
`
`5,883,103
`
`
`
`g
`h
`
`(f)
`
`l
`
`
`
`
`
`
`
`Tween Span
`is N E
`Tweedspan N
`
`
`
`
`
`L44 10%
`
`Labrasol uB N
`
`Labrasol 10%
`
`
`
`
`
`d S 9 d S
`
`9
`
`o O o O C
`
`* Transport
`
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`

`U.S. Patent
`
`Mar 16, 1999
`
`Sheet 4 of 15
`
`5,883,103
`
`:
`
`A O Q S.
`
`i
`
`ND
`NSC
`N B
`S Plu44 Sol A
`
`N
`
`N
`
`N
`NTween A
`NND
`NC
`N B
`N Plu 44 A
`ND
`N
`
`N
`NLab A
`Hanks
`
`Transport
`
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`

`U.S. Patent
`
`Mar 16, 1999
`
`Sheet 5 of 15
`
`5,883,103
`
`?y
`us
`l
`
`ND
`NC
`s NB
`NTween A
`ND
`NC
`NB
`N L44A
`ND
`NC
`NB
`N Labrasol A
`Control
`
`% Transport
`
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`

`

`U.S. Patent
`
`Mar 16, 1999
`
`Sheet 6 of 15
`
`5,883,103
`
`i
`
`OCM Sq
`O O
`O 8 8 V.
`O.
`
`O.
`
`O
`CN
`SLabraf lipo 10%
`NLabraf lipo 5%
`S Labraf lipo 13
`NLabra hydro 10%
`Labra hydro 5%
`Labra hydro 13
`Plu oleigue10%
`Plu oleigue 5%
`NPlu oleigue 1%
`NNLabrasol 10%
`N,NLabrasol 5%
`NNLabrasol 13
`Labraf cm-10
`NN 1 O 3
`Labraf cm-10
`NXN 53
`Labraf cm-10
`N
`13
`Control
`N
`
`w
`
`% Transport
`
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`
`

`

`U.S. Patent
`
`Mar 16, 1999
`
`Sheet 7 of 15
`
`5,883,103
`
`
`
`G estar"
`
`
`
`l NY Aleic
`
`
`
`Linolenic
`
`N
`Oleic
`N
`
`s
`C
`8: p.
`
`C. A
`r
`oO do El
`
`N
`
`a
`
`a
`
`.
`
`O
`
`a
`
`0
`
`(N
`
`- - - V - Y -
`
`% Transport
`
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`

`U.S. Patent
`
`Mar 16, 1999
`
`Sheet 8 of 15
`
`5,883,103
`
`NNNN Labrasol-SAT
`NTween 20-SAT
`N Tween 20
`NLabrasol
`NPlu L44
`NTween 20 pH 6.3
`NNTween 20 pH 5.5
`NTween 20 pH 3.7
`
`N Plu L44 pH5
`NPlu L44 pH 2.95
`NLabrasol pH 6.5
`NLabrasol pH 5.4
`NLabrasol pH 3.65
`Hanks pH 7
`Hanks pH 5
`Hanks pH 3
`
`Y
`
`s
`
`& Transport
`
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`
`

`

`U.S. Patent
`
`Mar 16, 1999
`
`Sheet 9 of 15
`
`5,883,103
`
`
`
`
`
`
`
`
`
`N
`
`
`
`d o O d O O 9 O
`c
`as o O o O O o O O
`8
`D
`a
`8
`o
`n
`(N o o vo
`st"
`(Yi
`o
`
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`

`

`U.S. Patent
`
`Mar 16, 1999
`
`Sheet 10 of 15
`
`5,883,103
`
`
`
`TWeen
`20+SLS
`
`TWeen
`20+NaSall
`
`C C C Co O O. O. d Co
`Co O O O. O. O. O. d o
`to r" (N O CO. Vo (
`(N. O.
`
`O
`
`e
`
`o
`
`O
`
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`
`

`

`U.S. Patent
`
`Mar 16, 1999
`
`Sheet 11 of 15
`
`5,883,103
`
`
`
`NSF:
`
`
`
`
`
`labrasol 0.909
`N labra fac O. 454
`
`
`
`NSEE 8::
`
`
`
`labrasol 0.454
`labra fac O. 909
`
`
`
`labrasol 0.227
`labrafac 1 ... 1 36
`
`
`
`
`
`N Hanks
`N
`
`(S
`t
`
`CN o OO Vo
`was
`
`vs. CN O
`
`% Transport
`
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`

`

`U.S. Patent
`
`Mar 16, 1999
`
`Sheet 12 0f 15
`
`5,883,103
`
`s
`D
`O
`O
`
`Tween 20 PEG
`s N 4 OO
`S
`TWeen 20 PEG
`
`CN N 300 5
`Tween 20 PEG
`us N 200
`
`l N Tween 20 i.
`Pu L44 PEG
`4 OO N
`Plu L44 PEG
`3 OO N
`N Plu : PEG
`NPlu L44
`NHanks
`N
`o o O O C. d C o Co
`o o O C C C C Co o
`o r
`(N C Co
`Vo
`an
`N o
`-
`- V - V.
`
`
`
`
`
`
`
`
`
`O
`
`à Transport
`
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`
`

`

`U.S. Patent
`
`Mar 16, 1999
`
`Sheet 13 of 15
`
`5,883,103
`
`NK 60/30
`s
`f NJ 40/10
`(y) NI 60/10
`- NH 80/10
`CD
`NG 40/30
`u
`F 20/70 N
`NE 40/50
`D 1 O/1
`N /10
`NC 20/40
`SSB 6/90
`N 27/6
`
`O O
`O O O O O C
`O O O O O O O O
`
`es
`w-
`
`(N
`w
`
`O CO
`vm
`
`VO
`
`s
`
`(N
`
`C
`
`N Hanks
`N
`
`% Transport
`
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`
`

`

`U.S. Patent
`
`Mar 16, 1999
`
`Sheet 14 of 15
`
`5,883,103
`
`
`
`N ti-44
`
`
`
`
`
`s:-" 9
`
`
`
`N L-44 2
`
`
`
`
`
`
`
`N"-"
`
`NHanks
`
`o O O 9 O d d cs
`o O O C C d d 5
`a
`rt
`(N O Co
`Vo
`r
`on
`c.
`
`s
`
`e
`
`& Transport
`
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`

`

`U.S. Patent
`
`Mar 16, 1999
`
`Sheet 15 of 15
`
`5,883,103
`
`n
`
`44+Lauric
`
`L44+Glycon P
`N 45
`
`N&E in
`L44+ 11.3%
`NMyristic Acid
`E L 44 + 1 3.33
`N Cetary OH
`D Tw/Sp uE
`N 120pg/ml
`
`N C 480 ug/ml
`NB 240ng/ml
`A L44 uB 120 N Jug/ml
`
`Hanks
`
`& Transport
`
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`

`1
`ORALACYCLOVR DELIVERY
`
`5,883,103
`
`The present invention relates to the field of pharmaceu
`tical preparations of acyclovir, particularly preparations
`which can be administered orally.
`Acyclovir has proven to be safe and effective in the
`treatment of herpes simplex virus (HSV), cytomegalovirus
`(CMV) and varicella-zoster in immunocompromised and
`immunocompetent patients O'Brien, 1989). The Suppres
`Sion of reactivated or newly acquired viral diseaseS Such as
`genital herpes simplex or shingles for varicella-Zoster as
`well as acute varicella-Zoster infections has been achieved
`by oral administration of acyclovir Spruance, 1993;
`Balfour, 1993). Morbidity and mortality from viral disease
`have been reduced by pre- and postoperative prophylaxis
`with long-term (>6 months) oral acyclovir therapy Elkins,
`1993; Fletcher, 1991; Prentice, 1994; Paya, 1993). Concur
`rent acyclovir and AZT(azidothymidine) therapy has
`extended the survival of AIDS patients by one year when
`acyclovir therapy was begun at time of diagnosis Stein,
`1994). Acyclovir therapy for acute varicella-zoster disease
`reduces fever, chronic pain, the progression of rash and
`accelerates cutaneous healing Balfour, 1993).
`Acyclovir, is currently marketed as capsules (200 mg)
`tablets (800 mg) and Suspension for oral administration
`McEvoy, 1993; Barnhart, 1994). Orally administered acy
`clovir is slowly and erratically absorbed with 15-30%
`bioavailability O’Brien, 1989; Barnhart, 1994). Over half
`the dose of the currently marketed formulation is recovered
`in the feces Schaeffer, 1978). Failure to respond to acyclo
`Vir therapy may arise from an inadequate dose (frequency of
`dose or total daily dose); patient noncompliance; malabsorp
`tion in the intestine; or, resistant viral Strains Mindel, 1993).
`The need for readily absorbed oral antiviral agents has been
`identified as imperative for treatment of viral diseases to
`both patient populations Since long term IV treatment is
`restrictive and compliance with oral acyclovir is difficult.
`Katlama, 1993). An acyclovir preparation for oral delivery
`which permitted lower dosing and less frequent administra
`tion would facilitate compliance.
`The oral acyclovir preparations of the invention are
`designed to overcome the above failings and may be
`utilized, interalia, for prophylaxis of immuno-compromised
`patients; Suppression of latent or recurrent viral infection(s);
`preemptive therapy; and treatment of acute viral infections.
`Accordingly, the present invention provides a pharma
`ceutical preparation for oral delivery of acyclovir compris
`ing a stable hydrophobic emulsion comprising a continuous
`phase of a hydrophobic material Selected from the group
`consisting of a long chain carboxylic acid, long chain
`carboxylic acid ester, long chain carboxylic acid alcohol and
`mixtures thereof and a discontinuous phase of a hydrophilic
`material (water-in-oil) having acyclovir therein in a dosage
`form suitable for oral delivery. The hydrophobic continuous
`phase and the hydrophilic discontinuous phase can each
`independently be Solid, Semisolid or liquid. The acyclovir is
`soluble in the hydrophilic material. Preferably the carrier
`emulsion is a microemulsion, Sometimes designated herein
`as “uE”.
`In a preferred embodiment, the invention provides a
`pharmaceutical preparation comprising a water-in-oil
`emulsion, preferably a microemulsion, containing an oil
`phase (such as a long chain carboxylic acid or ester or
`alcohol thereof), a Surface active agent (Such as a
`poloxamer) and an aqueous phase containing the acyclovir.
`The advantage of using a water-in-oil microemulsion is that
`it has the ability to dissolve relatively large amounts of polar
`
`15
`
`25
`
`35
`
`40
`
`45
`
`50
`
`55
`
`60
`
`65
`
`2
`Solutes in an overall oily environment, creating a System for
`oral delivery of active acyclovir.
`The invention will now be further described by reference
`to a brief description of each of the accompanying drawings.
`The brief description and the drawings are in no way a
`limitation of the invention.
`FIG. 1 graphically illustrates the in situ transport of
`acyclovir in the microemulsion formulation of Example 2.
`Specific activity of acyclovir in the plasma is shown as a
`function of time. Three microemulsion formulation
`(Pluronic L44, Labrasol/Labrafc CM-10 and Tween 20) and
`the control Solution of Hank's are shown.
`FIG. 2 graphically illustrates the in Situ transport of
`acyclovir in Solution, as described in Example 2. Acyclovir
`was dissolved into solutions of Surfactants (SDS, Pluronic
`L44 and Tween 20) and oil (linoleic). ZorivaxmTM was
`dissolved in a balanced Salt Solution at the same concentra
`tion as the Solutions. The Specific activity of acyclovir
`transported per hour is shown.
`FIG. 3 graphically illustrates the increase in acyclovir
`transport in Surfactant Solutions and in microemulsions
`made with these Surfactants as described in Example 3.
`FIG. 4 graphically illustrates percent transport of acy
`clovir with increasing concentrations of drug in the micro
`emulsions and L44 Solutions, described in Example 4,
`showing that percent transport is not reduced with increasing
`concentration as might be the case if the mechanism were
`exclusively receptor mediated. Three microemulsion formu
`lations are compared with 10% surfactant solution.
`FIG. 5 graphically illustrates a confirmation of the data
`presented in FIG. 4 and Example 4.
`FIG. 6 graphically illustrates change in transepithelial
`electrical resistance (TEER) and transport with different
`concentrations of Surfactant in HBSS solution showing that
`acyclovir transport is proportional to increases in membrane
`fluidity and can be selectively modified with different
`Surfactants, and has reference to Example 5.
`FIG. 7 graphically illustrates change in TEER and trans
`port with different oily phases in HBSS solution showing the
`effect on intracellular junctions of different oily phases, and
`has reference to Example 6.
`FIG. 8 graphically illustrates acyclovir transport in
`microemulsions showing that transport can be further
`increased with decreasing pH and has reference to Example
`7.
`
`FIG. 9 graphically illustrates acyclovir transport with
`transport enhancing additives (EtOH, SLS, Brij 35, etc.) and
`has reference to Example 8.
`FIG. 10 graphically illustrates acyclovir transport in the
`presence of transport enhancerS Such as Sodium Salicylate
`and Sodium lauryl Sulfate, and has reference to Example 8.
`FIG. 11 graphically illustrates acyclovir transport in
`Pluronic L44 uE with labrasol and labrafacas co-surfactants,
`and has reference to Example 10.
`FIG. 12 graphically illustrates acyclovir transport with
`polyethyleneglycol (PEG)200, 300, and 400 added to the
`Pluronic L44 uE, and has reference to Example 11.
`FIG. 13 graphically illustrates acyclovir transport at
`different points on the Pluronic L44-linoleic acid phase map
`demonstrating the Specificity of the chosen proportions, and
`has reference to Example 12.
`FIG. 14 graphically illustrates acyclovir transport in the
`presence of a gelling agent (Myverol), and has reference to
`Example 13.
`FIG. 15 graphically illustrates acyclovir transport in the
`presence of Selected gelling agents and also has reference to
`Example 13.
`
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`

`5,883,103
`
`15
`
`25
`
`3
`The invention will now be described in more detail with
`respect to numerous embodiments and examples in Support
`thereof.
`The term “acyclovir is used herein to refer to 2-amino-1,
`9-dihydro-9-(2-hydroxy-ethoxy) methyl-6H-purin-6-one
`and the pharmaceutically acceptable Salts thereof. Acyclovir
`is an antiviral which inhibits human herpes viruses, includ
`ing herpes simplex types I (HSV-1) and 2 (HSV-2), varicella
`Zoster, Epstein-Barr virus (EBV) and cytomegalovirus
`(CMV). The inhibitory activity of acyclovir is highly selec
`tive for these viruses. Acyclovir is not a substrate for the
`thymidine kinase (TK) expressed by uninfected normal
`cells. However, TK encoded by HSV, varicella Zoster, and
`EBV converts acyclovir into acyclovir monophosphate, a
`nucleotide analogue. The monophosphate is further con
`verted into diphosphate by cellular guanylate kinase and into
`triphosphate by a number of cellular enzymes. Acyclovir
`triphosphate interferes with viral DNA polymerase and to a
`lesser degree cellular C.-DNA polymerase. In vitro, acyclovir
`triphosphate is incorporated into growing chains of DNA by
`viral DNA polymerase and thereby terminates DNA repli
`cation. Acyclovir is preferentially taken up and Selectively
`converted to the active triphosphate form by herpesvirus
`infected cells. Thus, acyclovir is much leSS toxic in vitro for
`uninfected normal cells because leSS is taken up, leSS is
`converted to the active form and cellular C.-DNA polymerase
`is less sensitive to the effects of the active form.
`An emulsion is a dispersed System containing at least two
`immiscible liquid phases, a hydrophobic phase and a hydro
`philic phase. The emulsion comprises the dispersed phase,
`the dispersion phase and an emulsifying agent or Surfactant
`agent, except when the hydrophobic material is a “Self
`emulsifying ester, whereby it is possible to produce an
`emulsion without a separate emulsifying agent. Usually one
`of the two immiscible liquids is an oil while the other is
`aqueous. Which phase becomes the dispersed phase depends
`on the relative amounts of the two liquid phases and which
`emulsifying agent is Selected. Therefore, an emulsion in
`which the aqueous phase is dispersed as droplets throughout
`the hydrophobic phase is called an water-in-oil (w/o) emul
`Sion and vice versa. The term “colloidal' refers to emulsions
`in which the dispersed phase is of Very fine particles, usually
`less than about 1 mm in size. A "microcolloid” is an
`emulsion wherein the dispersed particles are usually about
`100 um or less in size. CoSurfactants are also common
`components of microcolloids and are Simply Surfactants
`included in addition to the primary Surfactant.
`A "microemulsion' is an optically clear, isotropic and
`thermodynamically stable liquid. Microemulsions are com
`posed of an oily phase, an aqueous phase, a Surfactant and,
`50
`Sometimes, a coSurfactant. A homogeneous mixture forms
`when components of the microemulsion are mixed together
`in any order. The resulting composition is thermodynami
`cally Stable with either a water continuous phase, an oily
`continuous phase, or a bicontinuous combination of the
`phases. Specifically, the microemulsion of the invention is a
`water-in-oil microemulsion, with the oil as the continuous
`phase.
`Microemulsions are ideal for oral acyclovir delivery
`Systems since they are homogeneous, thermodynamically
`Stable and have uniform droplet sizes of approximately
`20-40 nanometers. A water-in-oil microemulsion, in
`particular, has Small aqueous phase droplets, uniformly
`dispersed in the continuous oil phase. In general, the chemi
`cal Structure of acyclovir dictates that it will be at least
`somewhat, if not mostly, water soluble, and thus will be
`located inside the water droplet or very near the Surface of
`
`4
`the droplet of the water-in-oil microemulsion system. The
`outer oily phase of the microemulsion is able to incorporate
`into the intestinal cell matrix, thus creating channels (either
`paracellularly or transcellularly) through which the acyclo
`Vir can pass.
`One general preparation procedure that maximizes acy
`clovir Solubility is as follows: first, the acyclovir is prepared
`as a slurry in the aqueous phase at pH 2, Second, the
`Surfactant is added and mixed thoroughly; third, the oily
`phase is added and mixed to form the microemulsion. The
`ingredients of the microemulsion can be any of the below
`named Surfactants, oily phases or aqueous phases.
`In large-scale manufacture, these Steps can be accom
`plished using Standard mixing equipment employed in the
`production of ointments, creams and lotions. Specifically,
`mixing tanks made by Lee Industries (New Cumberland,
`Pa.) can be readily used. Regardless of the equipment
`employed, mixing needs to be accomplished using as low a
`Shear rate as practical, in order to maintain the physical
`integrity of the acyclovir.
`It is important to Select a hydrophobic material that can
`erode or degrade slowly in the intestine or become incor
`porated into the intestinal cell matrix So that the acyclovir is
`released. In addition, it is possible to combine the two
`approaches, for example, by incorporating enteric materials
`in the hydrophobic phase. This would preclude the necessity
`of coating the capsule with an enteric polymer.
`In accordance with the present invention, certain hydro
`phobic materials provide enhanced absorption capabilities
`for oral delivery of acyclovir. These materials are selected
`from the group consisting of long chain carboxylic acids,
`long chain carboxylic acid esters, long chain carboxylic acid
`alcohols and mixtures thereof.
`Further, certain materials, when combined in accordance
`with the invention to form a water-in-oil microemulsion,
`give enhanced absorption capabilities. These materials are
`an oily phase, composed of long chain carboxylic acids or
`esters of alcohols thereof, an aqueous phase composed
`primarily of water and Surface active agent, primarily of the
`non-ionic block copolymer type, that are mixed together to
`form a water-in-oil microemulsion.
`The long chain carboxylic acids, generally contain 4-36
`carbon atoms and preferably contain at least 12 carbon
`atoms, most preferably 12 to 22. In Some cases this carbon
`chain is fully Saturated and unbranched, while others contain
`one or more double bonds. They can have Saturated,
`unsaturated, branched or Straight chain hydrocarbon chains.
`A few contain 3-carbon rings or hydroxyl groups. The
`compounds are generally not Surface active. They are poorly
`Soluble in water and the longer the acid chain, the fewer the
`double bonds, the lower the solubility in water. The car
`boxylic acid group is polar and ionized at neutral pH. This
`accounts for the slight Solubility of short-chain acids in
`Water.
`Examples of Such acids are those ranging from C to C.
`with up to three unsaturated bonds (also branching).
`Examples of Saturated Straight chain acids are n-dodecanoic
`acid, n-tetradecanoic acid, n-hexadecanoic acid, caproic
`acid, caprylic acid, capric acid, lauric acid, myristic acid,
`palmitic acid, Stearic acid, arachidic acid, behenic acid,
`montanic acid and melissic acid. Also useful are unsaturated
`monoolefinic Straight chain monocarboxylic acids.
`Examples of these are oleic acid, gadoleic acid and erucic
`acid. Also useful are unsaturated (polyolefinic) Straight
`chain moncarboxylic acids. Examples of these are linoleic
`acid, ricinoleic acid, linolenic acid, arachidonic acid and
`behenolic acid. Useful branched acids include, for example,
`diacetyl tartaric acid.
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`Examples of long chain carboxylic acid esters include,
`but are not limited to those from the group of glyceryl
`monoStearates, glyceryl monopalmitates, mixtures of glyc
`eryl monoStearate and glyceryl monoalmitate (My vaple 600,
`Eastman Fine Chemical Company); glyceryl monolinoleate;
`glyceryl monooleate; mixtures of glyceryl monopalmitate,
`glyceryl monoStearate, glyceryl monooleate and glyceryl
`monolinoleate (Myverol 18-92, Eastman Fine Chemical
`Company); glyceryl monolinolenate; glyceryl monogado
`leate; mixtures of glyceryl monopalmitate, glyceryl
`monoStearate, glyceryl monooleate, glyceryl monolinoleate,
`Glyceryl monlinolenate and glyceryl monogadoleate
`(Myverol 18-99, Eastman Fine Chemical Company); acety
`lated glycerides Such as distilled acetylated monoglycerides
`(Myvacet 5-07, 7-07 and 9-95, Eastman Fine Chemical
`Company); mixtures of propylene glycol monoesters, dis
`tilled monoglycerides, Sodium Steroyl lactylate and Silicon
`dioxide (Myvatex TL, Eastman Fine Chemical Company);
`d-alpha tocopherol polyethylene glycol 1000 Succinate
`(Vitamin ETPGS, Eastman Fine Chemical Company); mix
`tures of mono- and di-glyceride esterS Such as Atmul
`(Humko Chemical Division of Witco Chemical); calcium
`Stearoyl lactylate; ethoxylated mono- and di-glycerides,
`lactated mono- and di-glycerides, lactylate carboxylic acid
`ester of glycerol and propylene glycol, lactylic esters of long
`chain carboxylic acids, polyglycerol esters of long chain
`carboxylic acids, Sodium Stearoyl lactylate, Sorbitan
`monoStearate; SOrbitan monooleate; other Sorbitan esters of
`long chain carboxylic acids, Succinylated monglycerides,
`Stearyl monoglyceryl citrate, Stearylheptanoate, cetyl esters
`of waxes, Stearyl octanoate; Co-Co cholesterol/lavosterol
`esters, and Sucrose long chain carboxylic acid esters.
`Examples of the Self-emulsifying long chain carboxylic
`acid esters include those from the groups of Stearates,
`pamitates, ricinoleates, oleates, behenates, ricinolenates,
`myristates, laurates, caprylates, and caproates.
`The alcohols useful in the invention are exemplified by
`the hydroxyl forms of the carboxylic acids exemplified
`above.
`Additives to the carboxylic acid/alcohol phase can be
`used to create a Solid at room temperature. This addition
`affords the opportunity to make better use of enteric coat
`ings. Examples of Such additives are glycerol behenate, cetyl
`alcohol, Stearic acid, Sorbitan ester derivatives Such as
`Sorbitan Stearate, Sorbitan isoStearate, polyethylene glycol
`1000 to 6000, saturated polyglycolised glycerides, acrylic
`polymers, glyceryl monoricinoleate, palmitic acid, myristic
`acid, and polyvinyl acetate.
`Such ingredients could be, but are not limited to, long
`chain carboxylic acids or esters of alcohols thereof which
`are paste or Solid at room temperature or which, upon
`incorporation into the microemulsion, form a gel, Such as
`glyceryl behenate, cetyl alcohol, Stearyl alcohol, Stearic acid,
`Sodium Stearate, Saturated polyglycolised glycerides, acrylic
`polymers, myverol 18-92, myverol 18-99, myvacet 9-45,
`vitamin E TPGS, vitamin E-6 - 100, glyceryl
`monoricinoleate, Gelucire 44-14, palmitic acid, myristic
`acid, polyvinyl acetate.
`Such a paste formulation is incorporated into a conve
`nient oral dosage form of the pharmaceutical agent. One
`Such dosage form is to incorporate the microemulsion into a
`gelatin capsule. The gelatin capsule can be either hard shell
`or soft shell. The preferred format of the invention is the soft
`shell gelatin capsule. The convenient oral dosage form
`would allow ease of Swallowing and may be coated with a
`polymer of the enteric coating type, Such that the polymer is
`impervious to an acidic environment like that found in the
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`Stomach, but would dissolve in a relatively basic environ
`ment like that found in the intestine.
`The types of protective or Sustained release coatings that
`can be used include, but are not limited to, ethylcellulose,
`hydroxypropylmethylcellulose, hydroxypropylcellulose,
`hydroxyethylcellulose and ester of methacrylic and
`ethacrylic acid (Eudragit RL, RS, and NE polymer products,
`Rohm Pharma, Darmstadt, Germany). The enteric protective
`materials or coatings can be, for example, cellulose acetate
`pthalate, hydroxypropylmethylcellulose pthalate, ethylviny
`lacetate pthalate, polyvinylacetate pthalate and esters of
`methacrylic and ethacrylic acid (Eudragit S, Eudragit Land
`Eudragit E30D, Rohm Pharma, Darmstadt, Germany).
`The composition or preparation of the invention can
`further include a Surfactant, or a mixture of two or more
`Surfactants. A Surfactant is an amphiphilic molecule consist
`ing of a hydrophobic tail and a hydrophilic head. These
`molecules possess distinct regions of both hydrophilic and
`hydrophobic character. The hydrophobic tail can be a hydro
`carbon or fluorocarbon chain of 8 to 18 carbon atoms. They
`are long chain molecules Such as, for example, Soaps or
`detergents. Surface active agents or Surfactants are long
`chain molecules, Such as Soaps and detergents, which accu
`mulate at the hydrophilic/hydrophobic(water/oil) interface
`and lower the Surface tension at the interface. One effect of
`the reduced Surface tension is the Stabilization of the emul
`Sions. This is because molecules with both polar and non
`polar groups become oriented Such that the hydrocarbon tail
`embeds itself into the hydrophobic phase and the hydro
`philic head protrudes into the hydrophilic phase. Where the
`hydrophobic composition or other component of the prepa
`ration includes a Surface-active agent, Such as a Surfactant,
`it is usually present in amounts of about 0.05% to 50.0%
`weight/weight of the hydrophobic composition with a pre
`ferred range of 1.0% to 3.0% (w/w). Preferred surfactants
`include, for example, the Tween (polyoxyethylene Sorbate)
`family of surfactants (ICI, Wilmington Del.), the Span
`(Sorbitan long chain carboxylic acid esters) family of Sur
`factants (ICI), the Pluronic (ethylene or propylene oxide
`block copolymers) family of Surfactants (BASF, Parsippany
`N.J.), the Labrasol, Labrafil and Labrafac (each polyglyco
`lyzed glycerides) families of Surfactants (Gappe Fosse, St.
`Priest, France), Sorbitan esters of oleate, Stearate, laurate or
`other long chain carboxylic acids, polo Xamers
`(polyethylene-polypropylene glycol block copolymers or
`the Pluronic brand surfactants, BASF Inc. Parsippany, N.J.),
`other Sorbitan or Sucrose long chain carboxylic acid esters,
`mono and diglycerides, PEG derivatives of caprylic/capric
`triglycerides and mixtures thereof.
`Microemulsions are generally formed by adding the
`aqueous phase, oily phase, and Surfactant to a Suitable vessel
`and mixing. If any of the ingredient is a Solid, it should be
`added to a liquid phase in which it is Soluble and heated to
`dissolve. For example, if the Surfactant is a Solid, and it is
`soluble in the oily phase, then it should be dissolved
`completely, then followed with aqueous phase, etc. On the
`other hand, if the Surfactant is Soluble in the aqueous phase,
`then it should first be added to the aqueous phase, dissolved
`completely, followed by the oil phase. Appropriate mixing
`devices as mentioned above can be employed for this
`purpose.
`The preparation of an water-in-oil emulsion based
`System, requires that the acyclovir be dispersed into the
`hydrophilic material as described above, with the hydropho
`bic phase being added in the presence of Surfactant of
`Self-emulsifying hydrophobic long chain carboxylic acid
`ester. This emulsion is then filled into a soft or hard gelatin
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`7
`capsule. The capsule may be further processed to provide
`gastric protection by enterically coating the capsule.
`In accordance with the invention, acyclovir is incorpo
`rated into the microemulsions by admixture using conven
`tional mixing devices and homogenizers used by Semi-Solid
`ointments and lotions, with agitation at Speeds common to
`emulsified products Such as creams and emulsions.
`Examples of common equipment employed are propeller or
`turbine mixers, homogenizers, colloid mills, ultraSonic
`mixer and microfluidizers. Examples of Such brand name
`mixing equipment are Lee Kettle, Gaulin mixer and
`Stephan. The shear of the agitation should be sufficient to
`form a Stable dispersion, but not too great to cause degra
`dation of the acyclovir. The shear forces will form aggre
`gates that have diameters ranging from 100-500 angstroms.
`Suitable homogenizers are available from Micromedics,
`Inc., Silverson, And APV Crepaco, Arde Barinco. Stephen
`and Fryma mixers can also be employed with Suitable
`vacuum to prevent formation of bubbles. Monitoring and
`evaluation of pH, Viscosity, Specific gravity and aggregate
`Sizes are necessary.
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`EXAMPLE 1.
`General Methodology for Transport of Acyclovir
`AcroSS Caco-2 Cells Using an Acyclovir
`Microemulsion Formulation
`The following materials were used as received to prepare
`the acyclovir microemulsion: Pluronic L44 (BASF,
`Parsippany, N.J.), Linoleic acid (Emerseol 315, Emery
`Group, Henkle, Cincinnati, Ohio), Hank's buffer (Biofluids,
`Rockville, Md.). The microemulsion consists of 27.3%
`Pluronic L44, 63.6%. Linoleic acid, and 9.95% Hank's
`buffer. The microemulsion was prepared with the incorpo
`rated acyclovir as follows.
`A Stock Solution of acyclovir was prepared by adding
`acyclovir to Hank's buffer. The surfactant Pluronic L44 was
`then added and mixed thoroughly. The linoleic acid was
`added last. The microemulsion is assumed to have a density
`of 1 g/ml.
`The Caco-2 cell line has been recognized as an appropri
`ate in Vitro Screening model for oral drug delivery. Caco-2
`cells are derived from a colon cancer and differentiate in
`culture to form intestinal epithelium similar to that found in
`the small intestine. The cells form a monolayer with many
`of the Specific properties of the epithelial lining of the
`intestine: they form a brush border with normal enzymes,
`they form tight junctions between cells, and they acquire the
`barrier properties of an enterocyte sheet. When grown on
`permeable Supports these cells can be used to Screen drug
`microemulsion formulations.
`Caco-2 colon carcinoma cells were obtained from Ameri
`can Type Culture Collection (R