`© 1993 Elsevier Science Publishers B. V. All rights reserved 0168-3659/93/$06.00
`
`21
`
`COREL00811
`
`Controlled buccal delivery ofbuprenorphine
`
`J.P. Cassidy, N.M. Landzert and E. Quadros
`Ciba-Geigy Corporation, Ardsley, New York, USA
`(Received 7 October 1992; accepted in revised form 13 November 1992)
`
`Buprenorphine is a potent opiate agonist-antagonist used in the treatment of both acute and chronic
`pain. Like many opiates, it has low oral bioavailability due to both presystemic metabolism in the wall
`of the gastrointestinal tract and extensive first pass metabolism. Controlled delivery of analgesics re(cid:173)
`sults in good pain relief and a lower total requirement for the drug. Buccal delivery offers advantages
`in terms of accessibility, avoidance of first pass metabolism and the ability to provide controlled deli v(cid:173)
`ery for extended periods of time. Buccal permeation of buprenorphine was measured in vitro and in
`vivo in the dog model using prototype non-woven and hydrogel systems. The fluxes of drug were iden(cid:173)
`tical from solutions and from non-woven systems in vitro, providing a reliable way of applying a drug
`solution to the mucosa without leaking. A model is described that permits screening of potential buccal
`systems in vitro to select a system for in vivo use. In vivo, steady-state plasma levels were obtained
`using both non-woven and hydrogel systems. Steady state was attained in 1 to 1.5 hand was maintained
`during the time of application of the system. Assuming that the flux in man is similar to that in the
`dog, controlled buccal delivery ofbuprenorphine would provide adequate analgesia over an extended
`period of time.
`
`Key words: Buccal; Buprenorphine; Analgesia; Controlled delivery; Hydrogels
`
`Introduction
`
`Buprenorphine, an opiate agonist-antagonist
`with 20 to 40 times the potency of morphine [ 1 ] ,
`is used in the treatment of both acute and chronic
`pain [ 2,3]. Like many opiates, it is extensively
`metabolized in both the gastrointestinal ( GI)
`tract and the liver [ 4,5] and is therefore a poor
`candidate for oral delivery. It is currently admin(cid:173)
`istered as repeated intravenous or intramuscular
`injections and as a sublingual tablet. In the con(cid:173)
`trol of pain, it has been reported that administra(cid:173)
`tion of an analgesic at a constant rate results in
`
`Correspondence to: E. Quadros, Ciba-Geigy Corporation, 444
`Saw Mill River Road, Ardsley, NY 10502, USA.
`
`both optimal patient comfort and a reduced total
`amount of analgesic [ 6]. Controlled delivery of
`buprenorphine may therefore, offer advantages
`in pain management.
`The buccal route offers several advantages for
`controlled drug delivery for extended periods of
`time. The mucosa is well supplied with both vas(cid:173)
`cular and lymphatic drainage and first-pass me(cid:173)
`tabolism in the liver and pre-systemic metabo(cid:173)
`lism in the GI tract are avoided. The area is
`obviously very accessible for placement and re(cid:173)
`moval of a delivery device. Polymeric systems
`with an impermeable backing could deliver drug
`in a unidirectional fashion to the mucosa and
`avoid loss due to swallowing. The ultimate aim
`would be to develop a small, thin, flexible de>rice
`
`DRL - EXHIBIT 1024
`DRL001
`
`
`
`22
`
`that would adhere to the mucosa during normal
`activities, including eating and drinking. Buccal
`delivery also offers the advantage of rapid ab(cid:173)
`sorption, which would obviously be necessary in
`the control of pain, and buprenorphine is known
`to be efficacious as a sublingual tablet [ 7]. The
`use of a device that provides rapid, long-lasting
`and adequate pain control by noninvasive means
`could offer considerable advantages in pain
`management.
`In the present study, the buccal absorption of
`buprenorphine was assessed in vitro in modified
`U ssing chambers [ 8]. Three different prototype
`systems, one non-woven and two hydrogels of
`varying water content, were assessed in vitro and
`in vivo in the dog~ Hydrogels have previously
`been used for the buccal delivery of diclofenac
`sodium in both the dog and man [9,10], and
`similar fluxes were measured in both species.
`Preliminary results of the current studies have
`been presented [ 11 , 12 ] .
`
`Materials and Methods
`
`Materials
`
`Buprenorphine hydrochloride was obtained
`from Diosynth (Bensenville, IL) and was used
`without further purification. Radioimmunoas(cid:173)
`say (RIA) kits were purchased from Diagnostic
`Products Corporation (Los Angeles, CA). t-Bu(cid:173)
`tyl peroctoate was from Pennwalt, Buffalo, NY,
`2-hydroxyethyl methacrylate
`(HEMA, Lot
`#64622) was obtained from Polysciences, Inc.,
`Warrington, PA, and monomer:macromer mix
`was kindly supplied by Dr. K. F. Mueller of Cen(cid:173)
`tral Research, Ciba-Geigy Corporation, Ardsley,
`NY. All other reagents were of HPLC or analyt(cid:173)
`ical grade and were used as purchased.
`
`Methods
`
`Analytical methodology
`
`HPLC. Buprenorphine was quantitated by re(cid:173)
`verse phase high performance liquid chromato(cid:173)
`graphy (HPLC) on a C-18 column ( 3 em, 3 pm
`particle size; Perkin-Elmer, Norwalk, CT) with
`
`fluorescence detection using an excitation wave(cid:173)
`length of 213 nm and a 360 nm emission cut-off
`filter. The mobile phase ( 60 I 40 acetonitrile I
`O.OlM KH2P04 , 0.01% TEA, adjusted to pH 3
`with phosphoric acid) was pumped isocratically
`at a flow rate of 1.5 ml/min. Standards were
`made up in the same solution as the samples
`being assayed. The standard curve was linear over
`the concentration range 25 ng/ml to 20 pg/ml,
`using an injection volume of 15 pl.
`
`RIA. Buprenorphine in Tris-phosphate sali:Qe
`[ 13 ] was measured using a modification of a
`commercially available kit. Briefly, 50 pl of sam(cid:173)
`ple (or standard) was incubated with 1 00 pi of
`1251] buprenorphine and 1 00 pi of antiserum at
`[
`room temperature for 1 h. Separation of anti(cid:173)
`body-bound from free buprenorphine was ac(cid:173)
`complished by the addition of a second antibody
`(goat anti-rabbit gamma-globulin), and centrif(cid:173)
`ugation at 25oC ( 1500xgfor 30 min). The pel(cid:173)
`let, containing antibody-bound material, was
`counted using a gamma counter (Minaxi Gamma
`Model 5000, Packard Instrument Company,
`Downers Grove, IL). The amount of buprenor(cid:173)
`phine was calculated from the standard curve
`which ranged from 0.05 to 15 ng/ml. Samples
`were assayed undiluted or at a dilution of 1 : 5 or
`1 : 20. The assay was validated at all dilutions
`studied and stability of buprenorphine was con(cid:173)
`firmed in buffer stored at -70oC for up to 21
`days prior to analysis.
`
`Solubility ofbuprenorphine hydrochloride
`The solubility of buprenorphine HCI was de(cid:173)
`termined by the addition of excess drug to either
`phosphate buffers [ 14, 15 ] or physiological buffer
`(Tris-phosphate saline) with initial pH values
`between 4 and 8. The vials were capped, vor(cid:173)
`texed and placed in a shaking water bath at 25 oc
`for 24 h. 1.5 ml of solution was removed, centri(cid:173)
`fuged in a microfuge (Model 235B, Fisher Sci(cid:173)
`entific, Springfield, NJ) at 15000xg for 2 min
`at room temperature and diluted for determina(cid:173)
`tion of buprenorphine by HPLC. The pH of the
`solutions was measured to give the final pH of
`the solutions.
`
`DRL - EXHIBIT 1024
`DRL002
`
`
`
`Buprenorphinejlux across buccal mucosa in vitro
`Male New Zealand White rabbits (2-4 kg)
`were sacrificed by carbon dioxide inhalation and
`beagle dogs of either sex (7-11 kg) were sacri(cid:173)
`ficed by an intravenous overdose of Nembutal®
`and exsanguination. All animal experimentation
`was performed according to protocols approved
`by Ciba-Geigy's Animal Care Committee. Buc(cid:173)
`cal tissue was removed by blunt dissection, sep(cid:173)
`arated from underlying muscle, rinsed in buffer
`and mounted in modified Ussing chambers
`(WPI, Sarasota, FL). Equilibration wasin 10 ml
`Krebs-Henseleit buffer [ 16], containing 10 mM
`glucose. The pH was maintained at 7.4 by bub(cid:173)
`bling with 95o/o 0 2 / 5o/o C02 and the temperature
`was maintained at 37oC by water-jacketing. The
`tissue was equilibrated for 30-60 min before drug
`donor solution was added to the mucosal side and
`fresh buffer was added to the serosal side. Sam(cid:173)
`ples (0.5 ml) were taken at intervals from the
`serosal side and the volume replaced with buffer.
`Samples were assayed for buprenorphine con(cid:173)
`tent by RIA or HPLC. Due to the low solubility
`ofbuprenorphine at neutral pH, some flux stud(cid:173)
`ies were performed at pH 4 using Tris-phosphate
`saline buffer. To monitor tissue viability, tran(cid:173)
`sepithelial potential difference and short-circuit
`current were measured by salt bridges of2% agar
`in Krebs-Henseleit buffer in contact with Ag/
`AgCl electrodes connected to a voltage current
`clamp (DVC-1000, WPI, Sarasota, FL) via a
`preamplifier.
`
`Preparation of hydrogel discs
`The hydrogels were prepared by copolymeri(cid:173)
`zation of HEMA with a macromer synthesized
`by the reaction of polytetramethylene glycol
`(Polymeg®) with isophorone diisocyanate in a
`1 : 2
`ratio
`[ 1 7]. Both
`90: 10
`(mono(cid:173)
`mer:macromer, wt/wt) and 80:2Qhydrogel sys(cid:173)
`tems were assessed. 90: 10 and 80: 20 hydrogels
`were prepared by the addition of HEMA to a
`70:30 monomer:macromer mixture. After de(cid:173)
`gassing for 30 min, 0.2 wto/o oft-butyl peroctoate
`was added as initiator. The solution was placed
`between two Mylar® -covered glass plates with the
`appropriate Teflon® spacer around tb,t: perime(cid:173)
`ter. The polymer was crosslinked by placing the
`
`23
`
`mold at 80 o C for 1 h. After cooling, the polymer
`was removed and washed with 5 changes of 8 1 of
`distilled water. Discs were punched ·from the
`water-washed polymer, and remaining mono(cid:173)
`mer was removed by Soxhlet extraction in
`ethanol overnight. The extracted discs were dried
`in a vacuum oven at 45 o C for 24 h.
`For drug loading, the dried discs were weighed,
`placed in a solution of buprenorphine HCl ( 15
`wto/o in 70o/o ethanol/30o/o 0.01 M KH2P04, pH
`4) and stirred at 45 o C for 72 h. The loaded sys(cid:173)
`tems were removed, rinsed briefly in 70o/o ethanol
`and dried for 48 h at room temperature in a vac(cid:173)
`uum desiccator. Before use, the systems were
`placed in a 95% humidity chamber for 48 h at
`room temperature.
`
`Dissolution testing
`The release profiles of the systems were deter(cid:173)
`mined using dried discs in a standard dissolution
`apparatus with stainless steel baskets (Vander(cid:173)
`kamp 600, Van-Kel Industries, Chatham, NJ).
`Dissolution was determined in 500 ml of dis(cid:173)
`tilled water at 32 o C. At various time intervals,
`0.8 ml of the solution was withdrawn from the
`reservoir and assayed for buprenorphine content
`byHPLC.
`
`Systems application in vitro
`The fluxes of buprenorphine across canine
`buccal mucosa were measured from both non(cid:173)
`woven and hydrogel discs in vitro. Buprenor(cid:173)
`phine (220 ,ul of 10 mg/ml buprenorphine hy(cid:173)
`drochloride in 10 mM KH2P04 ) was pipetted
`onto the surface of the non-woven material. The
`system was applied to the buccal mucosa and
`mounted in the Ussing chamber. Hydrogel discs,
`prepared as described above, were applied to the
`mucosal surface, backed with Parafilm ® and
`mounted in the Ussing chamber. In all experi(cid:173)
`ments, the total exposed surface area was 1 cm2
`
`,
`
`Buccal absorption in vivo
`Beagles {7-11 kg) of either sex were fasted
`overnight and had free access to water until the
`time of experimentation. They we.re anesthe(cid:173)
`tized with sodium pentobarbital (approximately
`25 mg/kg) via a 22 G Abbocath® in the cephalic
`
`DRL - EXHIBIT 1024
`DRL003
`
`
`
`24
`
`vein and additional doses were administered to
`maintain anesthesia during the course of the ex(cid:173)
`periment. Cannula patency was maintained with
`an i. v. drip of sterile lactated Ring~rs ( 1 ml/
`min). Blood samples ( 3 ml) were drawn into
`heparinized Monoject® syringes and plasma, ob(cid:173)
`tained following centrifugation (2000Xg for 10
`min), was placed in microfuge tubes and frozen
`in a dry ice-ethanol bath. Samples were stored
`for up to 3 weeks at - 70oC.
`To determine the i.v. pharmacokinetics ofbu(cid:173)
`prenorphine, a 0.30 mg bolus of buprenorphine
`HCl in 1.5 ml of lactated Ringers solution was
`injected through a second catheter placed in the
`saphenous vein. The bolus was followed by 5 ml
`oflactated Ringers to insure injection of the total
`dose. Plasma samples were obtained over a 4 h
`period and assayed for buprenorphine content by
`RIA. The fit of the plasma profile to a biexpo(cid:173)
`nential equation was modelled using R-Strip
`(Micromath, Inc.) with a y2 weighting, and
`pharmacokinetic parameters were determined for
`each animal.
`To determine buccal delivery of buprenor(cid:173)
`phine, beagles were anesthetized as described
`above, and a zero time blood sample was taken.
`The inner cheek was blotted dry with gauze, the
`appropriate device ( s) was placed on the cheek
`and the area covered by an impermeable back~ng
`membrane held in place by a peripheral adhesive
`(Super Polygrip, Dentco, Inc., Jersey City, NJ).
`The device was left in position for 2 to 4 h. Blood
`samples were taken at intervals during the appli(cid:173)
`cation of the device and after its removal. All
`plasma samples were assayed for buprenorphine
`content by RIA. Results are expressed as the
`mean::!: 1 SEM.
`
`Results
`
`Solubility of buprenorphine hydrochloride
`
`At the end of the 24 h incubation period all
`vials contained undissolved material which was
`removed by centrifugation. The solubility ofbu(cid:173)
`prenorphine was highly pH dependent with the
`highest solubility seen at low pH ( 17.3 mg/ml at
`
`pH 4.2). The solubility at neutral pH was con(cid:173)
`siderably lower (52 ,ug/ml at pH 7.3) (Fig. l).
`Essentially, similar solubilities were measured in
`USP, phosphate, and physiological (TPS) buff(cid:173)
`ers, except at pH 4.2 when the solubility was con(cid:173)
`siderably lower in TPS ( 4.2 mg/ml).
`
`Buprenorphine flux across buccal mucosa in vitro
`
`The flux of buprenorphine in vitro was mea(cid:173)
`sured across buccal mucosa obtained from both
`rabbit and dog. The donor solutions were at sat(cid:173)
`uration ( 4.3 mg/ml) in TPS buffer, adjusted to
`pH 4 with isotonic citric acid. Steady-state fluxes
`were calculated by linear regression using the
`asymptotic region of the cumulative amount/
`time curve and the time lag (to steady-state) was
`determined from the intercept on the abscissa.
`The steady-state fluxes and time lags were
`4.2::!:0.6,ug/cm 2/hand2.7±0.1 h (n=6) in the
`rabbit and 22.3::!: 6.0 ,ug/cm2/h and 1.6 ±: 0.4 h
`(n=4) in the dog, respectively. In the rabbit,
`steady-state flux was linearly related to donor
`concentration over the range 0.04 to 4.3 mg/ml
`(Fig. 2, r=0.998 ). The addition of sodium azide
`(10 mM), a metabolic inhibitor, to the mucosal
`solution at the same time as the drug caused the
`abolition of the transepithelial potentilll differ(cid:173)
`ence and an approximately 1 0-fold increase in the
`flux of buprenorphine, with no attainment of
`steady-state within the experimental time period.
`
`..
`•
`
`0
`
`10
`
`•
`
`.... 0
`
`~ Cl .s
`~
`:g
`0
`G')
`
`0.1
`
`..
`
`•
`
`0
`
`..
`
`it
`
`I
`
`0.01 L_ ___ L . . _ __ ____j ___ _ .L ___ .....J
`
`6
`
`pH
`
`8
`
`•
`
`Phosphate
`
`•
`
`USP.
`
`o
`
`TPS
`
`Fig. l. Solubility of buprenorphine hydrochloride in phos(cid:173)
`phate, USP phosphate and physiological (TPS) buffers.
`
`DRL - EXHIBIT 1024
`DRL004
`
`
`
`M 1 =l- I 8exp{-D[2n+!]:n 2t/L 2
`
`Mco
`
`n=O
`
`(2n+ l) 1l
`
`25
`
`)
`
`{18)
`
`where: M 1 =total amount of drug released at time
`t, M==total drugloaded into hydrogel, D=drug
`diffusion coefficient, and L =thickness of
`hydrogel.
`The diffusion coefficient for buprenorphine
`can be calculated using an early time approxi(cid:173)
`mation of the above equation:
`
`This equation is accurate to within 1% for MJ
`Moo<0.6.
`The diffusion coefficients for buprenorphine
`were 6.6±0.72X 10- 5 and 2.2±0.14X 10- 6
`cm2 /h for the 90: 10 and 80: 20 hydrogels,
`respectively.
`
`Flux from systems in vitro
`
`Steady-state flux across dog buccal mucosa
`from a solution ofbuprenorphine ( 10 mg/ml in
`10 mM KH2P04, pH 4) was 87.1 ±30.3 pg/cm2 /
`h with a time lag of 1.3±0.33 h, n=7 (Fig. 4).
`The
`permeability
`coefficient
`was
`2.42 ± 0.84 X 10- 6 cmjs. The steady-state flux
`from the same solution loaded onto a non-woven
`chamber was 78.7 ±26.4 J.lg/cm2/h with a time
`
`soo.---------------------,
`
`400
`
`·e
`~
`" .a 300
`..
`i
`e-g 200
`~ g .,
`
`100
`
`0
`
`0
`
`~
`' 1 rfl j - o..,.... Non-woven
`
`-•- 10 mgtml
`n•10
`
`n•10
`
`T TJ~
`y-VT'l
`-"""i""
`
`1.
`
`5
`
`Time (hr)
`
`Fig. 4. Cumulative flux of buprenorphine across dog buccal
`mucosa from a solution of 10 mg/ml (n= 10) andfrom 220
`JLl of a I 0 mg/ml solution loaded on to a non-woven system
`(n= 10).
`
`Donor concentration (mg/mll
`
`Fig. 2. Relationship between donor concentration and steady(cid:173)
`state flux of buprenorphine across rabbit buccal mucosa in
`vitro. The number of experiments was between 4 and 6.
`
`, .,, .
`• ..
`f ..,
`•
`.2
`'0
`~
`
`80
`
`60
`
`40
`
`20
`
`-- 90:10
`
`n•3
`_.,_ 80:20
`n•3
`--....- Non-woven
`
`0~--~--~----~--~--_J
`0.00
`0.50
`1.00
`1.50
`2.00
`2.50
`
`Square root of time
`
`Fig. 3. Dissolution of buprenorphine from non-woven and
`hydrogel systems as a function of the square root of time in
`hours.
`
`Dissolution of buprenorpbine from systems
`
`The hydrogel discs were 1.9 cm2 and 0.138 mm
`thick. The release profiles ofbuprenorphine from
`90: 10 and 80: 20 hydrogel discs were linear with
`the square root of time for 1 and 2 h, respectively
`(Fig. 3). The release rates were 432±25 and
`173 ± 5 J.lg/cm2 /h- 112 for the 90: 10 and 80:20
`discs, respectively ( n = 3, for each system).
`Drug release from these monoliths that are ini(cid:173)
`tially swelled with water may be described by the
`equation:
`
`DRL - EXHIBIT 1024
`DRL005
`
`
`
`26
`
`lag of0.952:0.24 h, n=ll (Fig. 4). There was
`no significant difference between the flux from
`solution or from the non-woven device, suggest(cid:173)
`ing that the use of non-woven systems in vivo
`would be equivalent to the application of a solu(cid:173)
`tion to the buccal mucosa without the associated
`problems of leakage and clamping of the device
`in place. Although there was a fairly large varia(cid:173)
`tion in the fluxes among animals, the flux across
`tissue from a single animal was much more re(cid:173)
`producible. Paired experiments were performed
`using solutions, 90: 10 and 80: 20 hydrogel discs
`on buccal mucosa from 4 dogs in vitro in Ussing
`chambers (Fig. 5). The steady-state fluxes were
`65.02:19.0,20.82:3.1 and 10.42:2.4pg/cm2/h
`with time lags of 1.82:0.15, 1.42:0.21 and
`2.1 2: 0.12 h, respectively.
`
`Buprenorphine pharmacokinetics in the dog
`
`Representative plasma levels of buprenor(cid:173)
`phine following an intravenous bolus of 0.3 mg
`of buprenorphine hydrochloride are shown in
`Fig. 6. The pharmacokinetic parameters deter(cid:173)
`mined for each dog are shown in Table 1. The
`experimental data were fitted to a biexponential
`rate equation to give the following mean param(cid:173)
`eter values:
`C( t) = 79.2e< -5.B9>t + 7.5e< -0.33)1
`
`where C(t) is the plasma concentration in ng/
`
`250
`
`! 200
`
`.a 150
`~
`1:
`0.
`l; 100
`·" ~
`g.
`lD
`
`50
`
`0
`
`0
`
`)
`-·- 10 mg/ml
`-·- 80:20
`
`n•4
`-o- 90:10
`n•4
`
`n•4
`
`T/I
`T/l
`r/l
`r_......V
`T/!
`/e
`1
`-/! ~----~......-~
`~--
`-- -
`1
`... -
`_ ........ 8--Q--2 ~-·--i-~
`
`T_..,..-0
`
`4
`
`Time (hr)
`Fig. 5. Cumulative flux ofbuprenorphine across dog buccal
`mucosa from solution (I 0 mg/ml ), 90: I 0 and 80:20 hydro(cid:173)
`gel discs, n= 4.
`
`50
`
`· - - · · · - - - · - · · · · - - - - - - · -
`
`~
`E 40
`
`~
`1: 30
`
`0. g ..
`~ 20
`.0 ..
`.. a:
`~ 10
`
`0
`
`0
`
`2
`
`4
`
`Time (hr)
`Fig. 6. Representative plasma profile ofbuprenorphine fol(cid:173)
`lowing administration of a 0.3 mg intravenous bolus. The data
`points were fitted to the curve shown by the dotted line using
`the equation in the figure.
`
`ml at time t (h) after dosing. The mean clear(cid:173)
`ance value was 144::!:: 10 ml/min and the total
`volume of distribution was 26.3±2.31 (n=6).
`These values are similar to those reported in the
`literature [ 19].
`
`Buccal absorption in vivo
`
`Plasma buprenorphine levels following buccal
`application of one and three 1 cm2 non-woven
`devices are shown in Fig. 7. Steady-state levels
`(c •• ) were calculated from the linear portions of
`the cumulative area under the plasma concentra(cid:173)
`tion time curves (AUC) versus time plots and
`the time lag to steady-state was the intercept on
`the. abscissa (Fig. 8 ) . The steady-state plasma
`levels were 8.2± 1.1 (n=6), 1.6±0.06 (n=3)
`and 1.5 ng/ml (n=2) during the application of
`three 1 cm2 discs, four 0.5 cm2 discs and one I
`cm2 disc, respectively. Steady-state flux (Jss> was
`calculated from the following equation
`
`C,, x Clearance
`A
`
`J,,
`
`where A= area in em 2
`The steady-state fluxes were 22.0::!:: 3.4 pgj
`cm2 /h (n=6) from three 1 cm 2 devices, 7.0::!:: 0.3
`from four 0.5 cm2 discs and 12.7 ,ug/cm2 /h from
`a single 1 cm2 device. The steady-state flux ofbu(cid:173)
`prenorphine from the smaller (0.5 cm2
`} devices
`
`DRL - EXHIBIT 1024
`DRL006
`
`
`
`TABLE I
`
`Pharmacokinetic parameters for an intravenousbolus ofbuprenorphine hydrochloride ( 300 ,ug)
`
`Parame~er
`
`Dog No.
`
`616567
`
`991911
`
`99267
`
`996971
`
`581216
`
`487945
`
`Weight (kg)
`Sex
`A (ng/ml)
`a (h- 1 }
`B (ng/ml)
`PCh- 1
`)
`Clearance 1 (ml/min)
`Vi (I)
`
`9.5
`
`F
`74.5
`6.9
`7.5
`0.33
`151
`27.5
`
`10.5
`F
`156.3
`8.1
`9.5
`0.37
`110
`18.0
`
`10.2
`F
`64.8
`4.1
`8.9
`0.33
`116
`21.1
`
`10.2
`F
`66.4
`5.6
`6.2
`0.37
`173
`28.4
`
`10.2
`M
`59.3
`4.9
`6.8
`0.31
`148
`28.5
`
`11.8
`F
`53.7
`5.8
`6.2
`0.29
`163
`34.0
`
`27
`
`Mean±SEM
`
`10.4 ±0.3
`
`79.2 ± 15.7
`5.9 ±0.6
`7.5 ±0.6
`0.33±0.01
`± lO
`144
`26.3 +2.3
`
`1Clearance
`
`Dose
`Area under curve
`Clearance
`Terminal halflife"
`
`2
`
`Vd
`
`10
`
`8
`
`6
`
`..
`.
`~
`.s
`.E
`""'
`..
`~
`a
`::0 ..,
`E . 2
`•
`• ii:
`
`c;
`
`4
`
`I Removal
`t
`l T T T
`
`1
`
`1.
`
`T
`l
`
`T T
`T
`.L ~
`.L
`
`Removal
`
`t
`.-e--&-e....
`'s .....
`
`-s-~
`
`..o-G-
`e
`,P'
`
`--€r"
`
`------ 3x 1 cm2
`
`--o-- 1x1cm2
`
`T
`1 T
`l T
`1
`
`0
`
`0
`
`2
`
`4
`
`5
`
`6
`
`Time (hr)
`Fig. 7. Plasma levels of buprenorphine obtained after appli(cid:173)
`cation of one or three I cm2 non-woven buccal devices. The
`single device was applied for 3 h and the three devices for
`4h.
`
`was significantly lower than that from three I cm2
`devices (p<O.Ol ), when expressed on the basis
`of area.
`Using the 80: 20 hydrogels, steady-state plasma
`levelsof3.7±0;6ng/ml (n=3) and 1.6±0.4ng/
`ml ( n = 3) were achieved following application
`of one 3.75 cm2 and three I cm2 discs, respec(cid:173)
`tively (Fig. 9 ). The time-lags to steady-state were
`0.9 ±0.4 and 0.7 ±0.1 h, respectively. The steady(cid:173)
`state fluxes were 8.6±0.9 and 4.8 ±0.7 Jlgfcm2 j
`h from one 3.75 cm2 and three l cm2 discs re(cid:173)
`spectively. The flux from three 1 cm2 hydr~gel
`
`40
`
`~ 30
`.. .s
`g 20
`< .. > :;:: .. "3
`
`§ 10
`0
`
`0
`
`0
`
`T 1
`T 1
`
`- - - HT 3x1
`
`-~· 80:~0 1d.75
`
`2
`
`4
`
`5
`
`6
`
`7
`
`Time {hr)
`
`Fig. 8. Cumulative AUC versus time curves following the ap(cid:173)
`plication of non-woven and hydrogel systems to canine buc(cid:173)
`cal mucosa.
`
`discs was significantly lower than that from three
`1 cm2 non-woven discs (p<O.OI) and the time
`lag to steady-state was significantly longer (0.7
`vs. 0.3 h, p<O.OI ). Using the higher water con(cid:173)
`tent hydrogels of various sizes (0.5 to 3.75 cm2
`)
`steady-state plasma levels were not achieved and
`considerable variation was seen. The flux data are
`summarized in Table 2.
`
`Discussion
`
`The solubility of buprenorphine hydrochlo(cid:173)
`ride was highly pH dependent, with an exponen-
`
`DRL - EXHIBIT 1024
`DRL007
`
`
`
`28
`
`~ E 4
`.. 1:
`:g_
`:;
`1: ..
`0.
`~ ..
`.. ii:
`!i
`
`3
`
`2
`
`1
`
`0
`
`2
`
`5
`
`6
`
`7
`
`Time (hr)
`
`-+- 3x1cm1
`n=3
`
`Fig. 9. Plasma levels of buprenorphine following the buccal
`application of 80:20 hydrogel discs. The time of application
`for the 3. 75 cm2 disc was 4 hours and for the three I cm 2
`discs, 3.5 hours.
`
`TABLE 2
`
`In vivo fluxes ofbuprenorphine from prototype systems in the dog
`
`System•
`
`Non-woven
`JX 1 em'
`4X0.5cm2
`1x1 cm1
`
`80:20 hydrogels
`I x3.75 em'
`3x I em'
`
`Flux
`(flg/em 2/hr)
`
`Steady-state plasma
`concentration (ng/ml)
`
`22.0± 3.4
`7.0±0.3
`12.7
`
`8.2±1.1
`1.6±0.06
`1.5
`
`8.6±0.9
`4.8±0.7
`
`3.7±0.6
`1.6±0.4
`
`n
`
`6
`3
`2
`
`•N umber of systems X area of system.
`Results are the mean ± 1 SEM.
`
`tial increase in solubility as the pH decreased. Its
`behavior in solution was similar to that reported
`for fentanyl and sufentanil, which are also weakly
`basic narcotic analgesics [ 20]. The presence of
`salts at a physiological concentration decreased
`the solubility from 17.3 mg/ml in phosphate
`buffer to 4.2 mg/ml.
`The permeation of buprenorphine through
`rabbit buccal mucosa in vitro was linearly re(cid:173)
`lated to the donor concentration over the range
`0.04 to 4.3 mg/ml, which is supportive of pas(cid:173)
`sive diffusion as the mechanism oftransport. The
`permeability of canine buccal mucosa was about
`seven-fold greater than that of the rabbit, with
`
`permeability coefficients of 14.4 and 2. 7 x 10- 7
`cm/s, respectively. The relative permeability was
`similar to that reported for CGS 1661 7, a highly
`hydrophilic angiotensin converting enzyme in(cid:173)
`hibitor [ 8]. The addition of sodium azide, an
`uncoupler of oxidative phosphorylation, re(cid:173)
`sulted in significantly increased flux of bupren(cid:173)
`orphine across rabbit buccal mucosa. Azide
`abolishes the spontaneous transepithelial poten(cid:173)
`tial difference and the barrier properties of buc(cid:173)
`cal mucosa from a variety of species [ 8] _ The flux
`of buprenorphine was the same from a 10 mg/
`ml donor in free solution or loaded onto a non(cid:173)
`woven chamber, suggesting that the non-woven
`chamber in vivo would be equivalent to the ap(cid:173)
`plication of a drug solution to the mucosa. The
`use of cups containing solutions has been asso(cid:173)
`ciated with leakage and the problems of clamp(cid:173)
`ing a cup securely in position without it moving
`or compromising the blood supply to the area.
`The application of non-woven systems to the
`buccal mucosa for 3 to 4 h resulted in steady-state
`plasma levels which were maintained until the
`removal of the systems. The slower decline in
`plasma levels compared to the rapid fall after an
`intravenous dose suggests the presence of a de(cid:173)
`pot in the buccal mucosa. The lower flux from
`smaller systems even when corrected for area may
`reflect an edge effect which may be due to poor
`contact with the tissue. The 80: 20 hydrogel sys(cid:173)
`tems also produced steady-state plasma levels
`with a similar slow decline after system removal
`(Fig. 9), but the flux was significantly lower than
`that obtained during the application of non(cid:173)
`woven systems of the same size. The higher water
`content hydrogels gave rise to much more erratic
`plasma levels and steady-state was not achieved.
`
`Conclusions
`
`Steady-state plasma levels of buprenorphine
`were obtained in the dog using two different pro(cid:173)
`totype systems, one non-woven and the other a
`hydrogel. The lag times were less than I h in both
`cases which would therefore provide rapid deliv(cid:173)
`ery of this analgesic. Good analgesic effect was
`obtained in man with sublingual buprenorphine
`
`DRL - EXHIBIT 1024
`DRL008
`
`
`
`following a similar delay in absorption [ 7]. The
`dog has been reported to be a good model for man
`[ 9, 10] and extrapolation of these results to man
`suggests that the buccal route of delivery of bu(cid:173)
`prenorphine would be feasible and would offer
`an excellent treatment modality for pain relief.
`
`References
`
`R.C. Heel, R.N. Brodgen, T.M. Speight and G.S. Avery,
`Buprenorphine: a new strong analgesic, Curr. Ther. 5
`( 1979) 29-33.
`2 P.J.Q. Watson, H.J. McQuay, R.E.S. Bullingham, M.C.
`Allen.and R.A. Moore, Single-dose comparison ofbu(cid:173)
`prenorphine 0.3 and 0.6 mg i.v. given after operation:
`clinical effects and plasma concentrations, Br. J. An(cid:173)
`aesth. 54 (1982) 37-43.
`3 H. Adriaensen, B. Mattelaer and H. Vanmeenen, A long(cid:173)
`term open, clinical and pharmacokinetic assessment of
`sublingual buprenorphine in patients suffering from
`chronic pain, Acta Anaesthesia!. Belg. l ( 1985) 33-40.
`4 D. Brewster, M.J. Humphrey and M.A. McLeavy, Bili(cid:173)
`ary excretion, metabolism and enterohepatic circula(cid:173)
`tion ofbuprenorphine, Xenobiotica II ( 1981) 189-196.
`5 M.J. Rance and J.S. Shillingford, The metabolism of
`phenolic opiates by rat intestine, Xenobiotica 7 ( 1977)
`529-36.
`6 P.C. Rutter, F. Murphy and H.A.F .. Dudley, Morphine:
`controlled trial of different methods of administration
`for postoperative pain relief, Br. Med. J. I ( 1980) 12-
`13.
`7 R.E.S. Bullingham, H.J. McQuay, D. Dwyer, M.C. Al(cid:173)
`len and R.A. Moore, Sublingual buprenorphine used
`post-operatively: clinical obervations and preliminary
`pharmacokinetic analysis, Br. J. Clin. Pharm. 12 ( 1981)
`I 17-122.
`8 E. Quadros, J. Cassidy, K. Gniecko and S. LeRoy, Buc(cid:173)
`cal and colonic absorption ofCGS 16617, a novel ACE
`inhibitor, J. Controlled Release 19 ( 1991) 77-86.
`
`29
`
`12
`
`10
`
`9 C.D. Ebert, V.A. John, P.T. Beall and K.A. Rosenzweig,
`Transbuccal absorption of diclofenac sodium in a dog
`model, Controlled-Release Technology (1987), W.R.
`Good and P. Lee, Eds: American Chemical Society, pp.
`310-321.
`J. Cassidy, B. Berner, K. Chan, V. John, S. Toon, B. Holt
`and M. Rowland, Buccal delivery of diclofenac sodium
`in man using a prototype hydrogel delivery device, Proc.
`Int. Symp. Controlled Release Bioact. Mat. 16 ( I 989)
`91-92.
`11 E. Quadros and J. Cassidy, Buccal flux of buprenor(cid:173)
`phine in vitro, Pharm. Res. 8 ( 199 L) S-156.
`J. Cassidy and E. Quadros, Sustained buccal delivery of
`buprenorphine in the dog in vivo, Pharm. Res. 8 ( 1991 )
`S-155.
`13 S. Reiser and P.A. Christiansen, The properties ofNa +(cid:173)
`dependent and Na +-independent lysine uptake by iso(cid:173)
`lated intestinal epithelial cells, Biochim. Biophys. Acta
`307 (1973) 212-222.
`14 U.S. Pharmacopeia ( 1985) pp. 1419-1420.
`15 Geigy Scientific Tables, Vol. 3 ( 1984) C. Lentner, Ed.
`Ciba-Geigy, Limited, Basle, pp. 58-60.
`16 H.A. Krebs and K. Henseleit, Untersuchugen uber -die
`Hamstoffbildung im Tierkorper, Hoppe-Seyler's Z.
`Physiol.Chem.2IO (1932) 33-66.
`17 W.R. Good and K.F. Mueller, A new family of mono(cid:173)
`lithic hydrogels for controlled release application, Con(cid:173)
`trolled Release of Bioactive Materials, Academic Press,
`NewYork, 1980,pp.ISS-175.
`18 1. Crank, The mathematics of diffusion, 2nd ed., Clar(cid:173)
`endon Press, Oxford, 197 5.
`19 E.R. Garrett and V.R. Chandran, Pharmacokinetics of
`morphine and its surrogates X: analyses and pharma(cid:173)
`cokinetics of buprenorphine in dogs, Biopharm. Drug
`Disp. 11 ( 1990) 311-350.
`20 S.D. Roy and G.L. Flynn, Solubility behavior of nar(cid:173)
`cotic analgesics in aqueous media: solubilities and dis(cid:173)
`sociation constants of morphine, fentanyl and sufen(cid:173)
`tanil, Pharm. Res. 6 (I 989) 147-151.
`
`DRL - EXHIBIT 1024
`DRL009