CA1166960A

CA1166960A - Transdermal nitroglycerin pad

Info

Publication number: CA1166960A
Application number: CA000383561A
Authority: CA
Inventors: Dilip R. Sanvordeker; James G. Cooney; Ronald C. Wester
Original assignee: GD Searle LLC
Current assignee: GD Searle LLC
Priority date: 1980-08-11
Filing date: 1981-08-10
Publication date: 1984-05-08
Also published as: SE450338B; CH650672B; DK162876B; DK162876C; NL193135C; DK354981A; IE51490B1; GB2081582A; FR2488134A1; NL193135B; AU552363B2; DE3131610A1; GB2081582B; AU7393881A; NL8103753A; FR2488134B1; US4336243A; IE811819L; SE8104764L; DE3131610C2

Abstract

Abstract The present invention provides a trans-dermal delivery pad for nitroglycerin administration, specifically a microsealed, trans-dermal nitroglycerin pad having a backing which is impervious to nitroglycerin absorption and transport and a silicon matrix affixed thereto, said silicone polymer matrix being of cross-linked silicone rubber having from about 10 to 200 micron microsealed compartments being formed by in situ cross-linking of the silicone rubber after it is mixed with a hydrophilic solvent system containing the nitroglycerin and a hydrophilic solvent which enhances nitroglycerin dispersion and transport.

Description

~6&~

sackground of the Invention In recent years, various drug delivery systems have been developed which provide sustained release thereapy via a suh-dermal insert. Systems have been disclosed which also provide drug delivery systems suitable for transdermal drug administration.
U.S. Patent Mo. 3,964,106, commonly assigned, dis-closes a microsealed pharmaceutical delivery device suit-able for implantation or trans-dermal use, as well as vag-inal or intrauterine use.
It has now been found, that in the case of nitrogly- - ?
cerin as the drug to be~delivered, drug transport is greatly enhanced and drug~delivery increased if triglycerides of saturated coconut oil acids, i.e. migloyl oil 812, and iso-propyl palmitate alone, or in combination with mineral oil are added to compliment the hydrophilic solvent system in the poIymer matrix.
U.S. Patent No. 3,996,934 also discloses a medical ~bandage comprising a backing member and a facing member having at least one reservoir containing systemically active drug either as a dlstinct layer or as~a plurallty of micro-capsules distributed throughoùt a silicone polymer matrix. -~
Example one discloses a nitroglycerin pad.
It is also known that a nitroglycerin bandage may ~-contain from 1-10 parts of nitroglycerin per 100 parts of carrier. Mineral oil and lanolin are taught to enhance the transport and ,~ ' , ,''' ',~ .
, .

.

-2- ~I6~96~

absorption of nitroglycerin when the carrier is selected from the group consisting of polyethylene, polypropyléne, polybutylene or polyrnethylbutylene.
Despite the prior art teachings, the only topical form of ni~roglycerin corMnercially available at the present time remains ointments or creams which cause ~taining and r~quire relatively freauent applications over a much larger sufrace areas than is required by the nikroglycerin pad of the present invention.
Summar of the Invention ~ - .
The prese~t invention provides a transdermal delivery system for the administration of nitroglycerin, and more 3peci~ically provides a nitroglycerin pad which is conveniently applied to the skin to provide trans-15 dermal nitroglycexin administration over a prolongedperiod of time.
The pad of the present invention can vary in size depending upon the dosage needs of the individual p~tient. The preferred size is 2 x 4 cm. The pad 20 comprises a biologically acceptable silicone polymer matrix having ~icrosealed oompartments ~hroughout, the micro-: ~ealed compartments cQntainlng nitroslycerin in a hydrophllic solvent ~ystem wherein the ratio of the parti~ion of coefficient of nitroglycerin and the biologically acceptable 25 5ilicone polymer matrix to the solubility of nitroglycerin : in the hydrophilic solvent system is between 1 and 10-4 ml/mcg.
A hydrophobic solvent system~is also incorpoxated to enhance diffusion of the nitroglycerin throughout the matrix.
~ The nitroglycerin i~ dispersed throughout the matrix, preferably : 30 as a ~itroglycerin-lactose mixture for ease and safety of handlins being diffusable through the biologically acceptable ~ilicon polymer matrix at a therapeutically effective rate when the : pad is in contact with the skin~ ~he pad is designed in such a way ~hat the liquid on the surface of the pad acts 35 both as a primary contact between the skin and the pad, as well as a trigger, and promotes diffusion ar-d absorption from the pad and into the skir~.

-2a~

Materials used -to form the biologically acceptable polymer container are those capable of forming thin walls or coatings through which pharmaceuticals can pass at a controlled rate. Suitable polymers are bio-logically and pharmaceutically compatible, non-allergenic and insoluble in and non-irritating to body fluids or tissues with which the device is contacted. The use of soluble polymers is to be avoided since dissolution or erosion of the device would affect the release rate of the pharmaceutical release rate, as well as the capability of the device to remain in place for convenience of removal.
Exemplary materials for fahricating the biologically acceptable polymer container include polyethylene, poly-propylene, ethylene/propylene copolymers, ethylene/ethy-lacrylate copolymers, ethylene/vinyl acetate copolymers,silicone rubbers, especially the medical grade polydi-methyl siloxanes, neoprene rubber, chlorinated polyethy-lene, polyvinyl chloride; vinyl chloride copolymers with vinyl acetate, poly methacrylate polymer(hydrogel), vinylidene chloride, ethylene and propylene; polyethylene terephthalate; butyl rubber; epichlorohydrin rubbers;
ethylene/vinyl alcohol copolymer; ethylene/vinyloxyethanol copolymer; and the like. For best results, the biologically acceptable polymer container should be selected from polymers of the above classes with glass transition temper-atures below room temperature. The polymer may, but need not necessarily, have a degree of crystallinity at room temperature.
The preferred biologically acceptable silicone polymer matrix material is selected :Erom room temperature or elevated temperature cross-linking silicone rubber (polydimethyl siloxane) such as silicone polymers represented by the formula:

-3-R

- C13 - L ~c j3 -~ - si- ~ o ~ o-- ~ o~--CH3 n CH3 n I

~ 3 ~ Si ~ ~
I

CH3 n wherein ~ is Cl-C7 alkoxy, vinyl or allyl and wherein n is about 100-5000.
Suitable polymers are capable of forming thin walls or coatings through which nitroglycerin can pass at a controlled rate, are biologically and pharmaceutically compati~le, non-allergenic and insoluble in and non--irritating to the skin, and preferably have the following parameters:
.
Parameter Value Durometer hardness 30-100 shore A
Tensile Strength 500-700 psi,Die C
Elongation 100-400%,Die C
Tear Strength 70-lOO,ppi,Die B
The hvdrophilic sol~ent system employed in the practice of this invention generally comprises from about 10 to 30 volume percent of polyethylene glycol, preferably polyethylene glycol 400 in distilled water.
The hydrophilic solvent system is embedded with the hydrophobic solvent system within the silicone matrix.
The combined solvent systems incorporated within the matrix serve the unic~ue purpose of partitioning and enhancing the diffusion b~ nitroglycerin throughout the matrix, there~y allowing delivery of nitroglycerin at a controlled rate after the pad has been applied to the skin. Mitroglycerin is then allowed to diffuse through the pad into the skin for absorption to provide the desired pharmacological effect.

~4~

The hydrophobic solvent system comprises from about 5 to 15 weight percent of a compound selected from the group consisting of isopropyl palmitate, mineral oil, cholesterol or a triglyceride of a saturated coconut oil acid such as miglyol oil, or a mixture thereof. The in-corporation of isopropyl palmitate alone, or in combination with, for example, mineral oil or cholesterol, improves the transport and absorption of nitroglycerin.
It is preferable to admix from about 6 to 22 weight percent of a commercially availabl~ 10 percent nitroglycerin-lactose mixture into the hydrophilic solvent system prior to the preparation of the pad of the present invention.
Detailed Description o Pre~-r:ed Ltb~di~e~
A preferred embodiment of the present invention is a microsealed, transdermal nitroglycerin pad having a backing which is impervious to nitroglycerin absorption and transport, and a silicon polymer matrix affixed thereto, the silicone polymer matrix being of cross-linked silicone rubber having from about 10 to 200 micron microsealed compartments being formed by in situ cross-linXing of the silicone rubber after it is mixed with the hydrophilic solvent system containing the nitroglycerin and the hydrophobic solvent system which enhances nitroglycerin transport and dispersion, the nitroglycerin being diffusible through the bioloyically acceptable sillcon polymer matrix at a therapeutically effective constant rate when the ~P microsealed nitroglycerin pad is affixed to the skin, said hydrophilic solvent bein~ non-diffusible through the biologically ac~eptabl~ polymer ma~rix.
~ most preferred embodiment of the present invention is a microsealed 7 transdermal nitroglycerin delivery device comprising a biologically acceptable silicone polymer matrix constructed of silicone polymers represented by the formula:

-4a-_ .

--~ O ~ Sji ~ ~r O ~ si-- ~ ~ si-- 0~ __ CH3 l CH3 _ ~ q CH3 ~ Sl ~ 0 _ CH3 I
wherein R is alkoxy, alkyl, phenyl, vinyl or allyl and wherein n is abou-t 100 to 5000 and wherein the bioloyically acceptable silicone polymer matrix has microsealed compartments distributed throughout, said microsealed compartments containing from 6 to 22 weight percent of 10 weight percent nitroglycerin mixed with lactose in a hydrophillic solvent system comprising water, from 10 to 30 volume % polyethylene glycol, and from 5 to 15 weight percent of a hydrophobic solvent selected from the group consisting of mineral oil, oils derived from coconut oil or mixtures thereof. Representative coconut oil derivatives include isopropyl palmitate and miglyol oil. The microsealed compartments are formed by in situ cross-linking of the liquid silicone polymer after it is emulsified with the hydrophillic solvent system containing the nitroglycerin and the hydrophobic solvent.
Generally speaking, to prepare the transdermal nitroglycerin pad of the present invention, a saturated solution of a 10 percent nitroglycerin-lactose mixture is prepared in a suitable hydrophillic solvent system such as 10-30 (v/v) percent polyethylene glycol 400 in distilled water. An excess amount of the nitroglycerin-lactose mixture is maintained in this preparation -to obtain a uniform paste after manual or mechanical mixing for approximately 5-10 minutes. This uniform paste is added to the sillcone elastomer, i.e., MDX 4-4210 elastomer, Dow Corning, Midland Michigan, along with the required amount of a hydrophobic solvent or a similar solvent mixture, such as mineral oil, isopropyl palmitate, or a mixture thereof. ~11 of these ingredients are mixed from 5 to 15 minutes in a low shear, explosion-proof mixing vessel maintained under a vacuum of from 45-70 cm. The polymerizing catalyst is added and ; mixing is continued under vacuum from about 15 to 30 minutes. The final mixture is viscous, and 6 ~

~b-is poured, with the aid of mixing equipment, into clean, dry stainless steel plates. In the case of 2 x 4 cm pads, suitable amounts of the final mixture are poured into 12" by 12" stainless steel plates fitted with a fr~e of a desired thickness ranging from 5.0 mm to 1.2 mm.
A suitable material, such as aluminum foil, is place~ on the poured material and top plates having the same dimensions as the bottom plates , ~ut without frames, are pressed to fill the molds with the polymerizing formulation. The molds are secured in pla~e with screws in four corners and placed v --5~
'in an air circulating oven at ahout 60C. After two hours, the molds are removed, cooled, and the cured pad material adhering to the aluminum foil is pulled off, cut into suitable size pads, e.g. 2 x 4 cm with aluminum foi]. backingO The pads are then stored in air tight containers.
The pads preferably contain from about 6 to about 22 weighk percent of a commercially available 10 percent nitroglycerin-lactose mixture to provide the optimum, transdermal dosage. The optimum dosage was determined both from a series of bioa~ailability studies with neat nitro-glycerin as well as with pads of the present invention of differing dosages and thicknesses, as described in detail in the examples hereinbelow.
The followin~ examples further illustrate the ,present invention.
~xample 1 A 10 percent nitroglycerin-lactose mi~ture (55 g~, labeled with C14 nitroglycerin, was mixed for about 5 mi~utes with 25.0 g of 10 percent(v/vj polyethylene glycol 400 solution in deionized water. A uniform paste of the above mixture was added to 157.5 g of MDX 4-4210 silicone ~ elastomer(Dow Coxlling, Midland Michigan). Upon initial ; mixing for about 10 minutes under deaeration, a uniform dispersion was obtained in a low shear mlxer, To this dispersion was added 12.5 g of the curing agent for t~e MDX 4-4210 elastomer and mixing was continued for another 15 minutes. The final mixture was poured into 12" x 12"
stainless steel plates with a 5 cm frame to hold the curing material.Aluminum ~oil(12" x 12") was placed onto 30 each plate and pressed into the mold with a 12'i x 12"
stainless steel plate. The molds were secured with screws a~fixed on four corners and placed in an air-circulating oven at about 60C or approximately two hours.
Upon cooling, the polymer matrix, adhering to the aluminum foil as a backing, was removed from the molds and cut i~to 1.6 x 3.2 cm pads which were stored in air tight containers until use.

- ~66~

xampl2 2 A 10 percen~ nitroglycerin-lactose mixture(22 g), labeled with C14-nitroglycerin, was mi~.ed for about 5 mi~utes with 8 g of a 10 percent(v/v) polyethylene glycol solution in deionized water. A uniform paste of these ingredients and 20 g of mineral oil were added to 45 g of MDX 4-4210 silicone elastomer. Upon inl~ial mixing for 10 minutes under deaeration, a uniform dispersion was obtained in a low sheax mixer. To this mixture, 5 g of the curing agent were added and the mixing was continued for about fifteen minutes under deaeration. The final mixture was poured into stainless steel plates itted with a 5 mm thick frame.
A 12" x 12" piece of aluminum foil was paced on top and the mold~top plates were placed thereon, pressed and secured with scre~s affixed on four corners. The molds were placed in an air cir ulating oven at 60C for approximately two hours. Upon cooling, khe polymer matrix adhering to the ~` aluminum backing was remo~ed from the mold, cut into 1.6 x 3.2 cm pads and stored in air tight containers until use.
: E ~
Nitroglyceri~ pads (1.6 x 1.6 cm) were prepared ollowing th~ method of Example 2 f.r~m 11 g of 10 percent nitroglycerin-lactose, labeled with C14-nitroglycerin, 25 4.0 g o 10 percent (v/v) polyethylene glycol 400 in deionized water, 27O5 g of~.DX 4-4210 silicone elastomer, ; 5.0 g of isopropyl palmitate and 2.5 g of curing agent.
The pads were stored in airtight containers.

Following the method of Ex~mple 2, 2 x 4 cm nitroqlycerin pads were prepared from 22 g of 10 percent C14-labeled ~itroglycexin-lactose, 8.0 g of 10 percent (v/v) polyethylene glycol 400-deionized water solution, 20.0 g of miglyol 812 oil, 45.0 g of ~lDX 4-4210 silicone 3S elastomer and 5.0 g o~ curing agent. The pads wer~ stored in airtight containers until use.

69~
~7--Example 5 Nitroglycerin pads( 2 x 4 cm) were prepared following the method of Example 2 from 11 g of C14-labeled nitroglycerin-lactose mixture, 7 g of 10 percent~v/~) polyethylene glycol 400 in deionized water~ A uniform paste of the above ingredien~s and a mixture o~ 13.0 g of isopropyl palmitate and 6.0 g of mineral oil were added to 57 g of ~DX 4 4210 ~ilicone elastomex and, following initial mixing, 6.0 g of the curing agent wa~ added and the procedure of Exa~ple 2 followed thereafter.
The pads were stored in airtight containers until use.
Exam~le 6 . . _ Nitroglycerin pads (2 x 4 cm3 were prepared follo~ing the method of Example 2 from 11 g of C14-labeled 10 percent nitroglyc~rin-lacto~e, 4 g of 10 percent(v/v) polyethylene glycol 400 in deionized ~a~er, 5.0 g of iso-propyl palmi~ate, 5.0 g of mineral oil, 22.5 g of MDX 4~4210 silicone elastomer and 2.5 g of curing agent. The pads wPre stored in airtight containers until use.
~
~ ollowing the method of Example 2~ 2 x 4 and 1.6 x 1.6 cm nitroglycerin pads werP prepared ~rom 5.5 g of a C14-labeled 10 percent nitrog~ycerin-lactose mixture,

4.0 g of polyethyle~e glycol 400 in deionized water, 7.5 g of isopropyl palmita~e, 5,0 g of mineral oil, ?.5.5 g of MDX 4-~210 silicone elastomer and 2.5 g of curing agent.
The pads were stored in airtight containers until use.
Ex ~
Following the method of Example 2,2x~ cm paæ.s were m2de from 3 g of C14-labeled nitroglyr~erin in a 10 percent nitroglycerin-lactose mixture, 2.25 g of 10 percent(v~v) polyethylene glycol 400 in deionized water, 5~0 g of isopropyl palmitate,

5.0 g of mineral oil, 31.5 grams o~ MDX 4-4210 silicone elastomer~ Dow Corning, Midland, Michigan) and 3.25 g of the curing agent. The pads were stored in airtight containers until use.

Exam~le 9 Following the method o Example 2, 2 x 4 cm nitro-glycerin pads were prepared from 3 g of C14-labeled nitroglycerin in a 10 percent nitroglycerin-lactose mixture, 2.5 g of 1~ percent(v/v) polyethylene glycol 400 in deionizPd wa~er, 7.5 g of isopropyl palmitate, 5.n g of mineral oil, 29.5 g of MDX 4~4210 silicone elastomer an~
2.75 g o curing agent. The pads were stored in airtight containers until use.
~
Studies to determine the topical availability of nitroglycerin were carried out in ivo with the rhesus m~nkey(Macaca mulata). Percutaneous absorption in this animal model has been shown to be similar to man 15 for a number of compounds~
The animals were plàce in metabolism chairs for the lenyth of time of the dose application. Urine was collected while ~he animals were still in the metabolism chairs. After the dose was removed, the animals were 20 mo~ed to a meta~olism cage for continued urine collection.
Nitroglycerin,labeled with carbon-14,was applied to the skin. The site of application can be any part of the body; however, the ventral forearm or upper part of the ~: inner arm was used for convenience. The area of application 25 is generally small, i.e., 2-10 cm2; however, any area can be used. The final concentration is expressed as an amount per unit area o~ skin~i.eO 1.0 mg/ 1 cm2).
In the case o~ liquîd, cream or ointment formulations~ the dose was spread over the exact s~in area.
30 In the case o~ the pads uf the~ pxesent. invention, they ~: were taped to the skin. In the case of liquids, cream or ointments, the treated area was covered with aluminum foil and tape. In all cases, the tape and foil and where appIicable the nitroglycerin pad were re~oved after 24 hours and the 35 site of application was wiped three times with gauze so~kcd with ethanol, then washed with soap and water.
Absorption is quantlfied on the hasis of the p~rcent of radioactivity excreted in urine for ~ days ~ollowing application of a known amount of the labeled -9~

r roglyc~rin to th~ skin. Daily urinary excretion values are corrected for excretion of radioactivity by other routes and retention of radioactivity in the body ~y the administration of an intravenous dose of C14-labeled nitroqlycerin according to the following formula:
. %dose of radioactivitv in urine ~rcm topical xlOO
Perc~n~ Absorptln=%dDse of radioactivity Ln urine fro~ rV
In ~e case of C14-labeled nitroglyGerin applied via 10 the ni~ro~lycerin pad of ~he pxesent invention, the device can be removed ~rom the skin And analyzed for residual radloactivity. The amount of radioactivity which has been removed from the device, ~y cnmpArative assays with devices not appli~d to skin, is considered to have been 15 released in vivo during the time of ~kin application. Analysis _ _ _ for radioactivity can be conductsd using any commerically available liquid scintillation counter. To determine the amount of radioactivity in this study, l.O ml o~ radio-active urine was mixed with scintillation fluid(10 ml of 20 PCS~solubilizer, ~mersham Corporation, Arlington Heights, Illinois). The urine mixed with scintillant i~ counted for xadioactivity i~ a liquid scintillation counter and the amount of radioactivity determined.
The resul~s of neat nitroglycerin absorption are 25 set forth in Table I.The data show that i the topical concentration of nitroglycerin increases from 0.1 to 1.~ mg/cm~
: s~in area, the bioavailability of nitroglycerin remains equal to or grea~er than 40% for a 24 hour application.
Topical concentrations of 7 and 10 mg/cm~ showed decrease~
30 absorption and it was concluded that the aximum,optimum dosage for good bioavailability i5 5 mg/cm .
Table I
Percutaneous Absorption of C14 Nitroglycerin: Topi~al Concentratlon Versus _bsorption or Neat Li~uid Applic~tion _ 35 Topical Concentration Percent Dose Absorhed 0.01 41.8 ~ 3.2 0.1 43 5 ~ 3-3 1.0 36.6 ~ 3.7 7.~ 22.6 ~ 4.2.
10.0 7.8 ~ 0.7 g~ ~

The data for the in vivo release and bio-availability or nitroglycerin from the transdermal nitro-glycerin pads prepared according to the methods, of Examples l-9 are set forth in Table II. In Table II, the transdermal nitroglycerin pads are referred to as MDD-N.G
N.G. stands for nitroglycerin.
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2 5 C ~ -- CO ~ f O ~ I o ~ ~ N

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Literature reports on topical nitroglycerin ointment sug~es~ an effective clinical response from ap~roximately 20 to 40 mg of nitroglycerin(Cardiolo~y:63 337,1978; American Heart J. 96: 578,1978~.
It will be a~parent ~o those s~illed in the art that the nitroglycerin pads of Examples 1 9 were prepared wi~h C14-labeled nitroglycerin for purposes of bioavailability studies and that the pads are norma3.1y ~repared with unlat,eled nitroglyceri~. It will also be apparent to those skilled in the art that the lactose mixture is used for ease and safety of handling.
Exam~le 11 275 Grams of 10% nitroylycerin-lactose mixture was mixed with 175.0 g of 10% (v/v) polyethylene glycol 400 in deionized water. A uniform paste of these ingxedients, 325.0 y of isopropyl palmitate, 150.0 g of mineral oil and 150 g of curing agent for MDX 4-4210 were added to 142S.0 g of silicone elastomer MDX 4-4210. The mixture was mixed for 5 minutes without deaeration in a helicone 4 CV mixer (Atlantic Re~earch Corporation, Gainesville,VA) and the 20 mixiny was continued under a vacuum of about 60-70 cm for 30 minutes~ The final mix was poursd in suitable amounts(100-140 g) into 12"x12l' stainless steel plates with 1.3 mm frames. Aluminum foilwas placed atop the poured - material in each plate and pressed into the molds with 12" x 12" plates. The molds were secured with screws affixed on four corners and then placed in an air circulating oven at 60C for abo~t two hours. Upon coolins, the cured polymer matrix adhering to the aluminum foil w`as removed fr~m the molds, stored overnight covered with aluminum foil, and cut into 2 x 4" pads of app~oximately 2 mm thicknes The pads were packaged in SURLY ~ lam-inate foil(Ludlow Co., Lombard, Illinois) and stored in suitable containers.

.

Claims

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. A microsealed, nitroglycerin pad suitable for transdermal administration of nitroglycerin comprising a backing, a biologically acceptable silicone polymer matrix affixed to said backing, said silicone polymer matrix being of cross-linked silicone rubber having a plurality of 10 to 200 micron microsealed compartments therein, and containing therein from 10 to 30 volume percent of an aqueous hydrophillic solvent system comprising from about 6 to 22 weight percent of a mixture containing 10 weight percent nitroglycerine mixed with lactose therein, and from 5 to 15 weight percent of a hydrophobic solvent system, said hydrophobic solvent system being selected from the group consisting of mineral oil, a triglyceride of a saturated coconut oil acid and mixtures thereof, and said hydrophillic solvent being a polyethylene glycol.

2. The nitroglycerin pad of Claim 1 wherein said hydrophilic solvent system is an aqueous polyethylene glycol 400 solution.

3. The nitroglycerin pad of Claim 2 wherein said hydrophobic solvent is isopropyl palmitate.

4. The nitroglycerin pad of Claim 2 wherein said hydrophobic solvent is mineral oil.

5. The nitroglycerin pad of Claim 2 wherein said hydrophobic solvent comprises isopropyl palmitate and mineral oil.

6. The nitroglycerin pad of Claim 2 wherein said hydrophobic solvent is mineral oil and migloyl oil.