the polyethylene foamed material suitable for the dosage forms of this invention is available commercially in sheet form or roll stock , from which the dosage forms can be cut or punched , having a thickness varying from one - sixteenth inch to one thirty - second inch . the polyethylene foamed material can be made from ultra high molecular weight polyethylene or from high density polyethylene . suitable polyethylene foam materials can be obtained from porex technologies corporation of fairburn , ga . as porex x - 4900 , a fine polyethylene foam made from ultra high molecular weight polyethylene having a void volume of 45 % per unit of surface area , a 20 - 25 micron pore size and available in 12 inch square sheets having a thickness of one - sixtheenth inch . another foam material is porox p - 20 , a polyethylene foam made from high density polyethylene having a void volume of 40 % per unit of surface area , a 20 - 25 micron pore size and also available in 12 inch square sheets having a thickness of one - sixteenth inch . other suitable polyethylene foam materials can be obtained from chromex corporation of brooklyn , n . y . the polyethylene foam material can be heat - sealed to , for example , an aluminum foil laminate coated on its topside with a suitable heat - seal coating such as a coating of ethyl vinyl acetate , polyethylene or a polyvinylchloride . aluminum foil laminates can be obtained from meditect division of labeltape , inc . of grand rapids , mich . the polyethylene foam material heat - sealed to the aluminum foil laminate can have applied to its obverse surface a suitable adhesive coated flannel - cerex facestock , adhesive side up , and on top of the facestock a heavy weight white paper release liner . the flannel - cerex facestock is a skin adhesive backed by a soft white fine textured non - woven fabric . the effectiveness of the polyethylene dosage forms of the invention in transdermally delivering medication is shown in the following examples in comparison with polyurethane dosage forms . in the examples menthol was employed as a penetration enhancer as disclosed and claimed in copending application ser . no . 564 , 654 , filed dec . 22 , 1983 of andrew g . tsuk . other penetration enhancers can also be employed such as those described in u . s . pat . nos . 4 , 548 , 922 and 4 , 405 , 616 . patches were prepared by attaching a 5 . 1cm 2 circular disk of polyethylene foam , 1 / 16 &# 34 ; thick , 60 % void volume , 40 to 45 μ diameter pore size , to a suitable non - porous adhesive coated tape , approximately 6 cm × 6cm . polyurethane foam patches were prepared similarly using a 1 / 32 &# 34 ; thick foam , with 40 pores / linear inch . estradiol formulation was prepared and divided into aliquots . one aliquot was spiked with h 3 labelled estradiol and 400 mg of the formulation was applied to each polyethylene patch . a second aliquot was spiked with c 14 labelled estradiol and 250 mg was applied to each polyurethane patch . this amount of formulation was sufficient to fill the void volume of each patch . one of each of the two patches was applied to backs of each of 10 male albino rats one day following clipping . additional porous tape was used to hold the patches in place . the rats were placed in individual metabolism cages and urine was collected at 3 , 6 , 9 , 12 , 24 , 31 , 48 , 55 , and 72 hours after patch application . patches were removed 24 hours after application and the treatment site was washed with soapy water , rinsed and dried . urine samples were assayed for each radioactive isotope . results from the study are presented in fig . i and ii and show the rate or excretion of 17 - β - estradiol as a function of time . each point is the average value for the 10 rats treated . these data indicate that the polyethylene disk is an efficient system for transdermal delivery of estradiol . two patches were similarly prepared to those in example 1 . however , an additional layer of foam adhesive tape was applied to non - porous tape and placed concentrically around the foam disk . approximately 200 mg of c 14 labelled formulation was applied to the polyurethane disk and approximately 415 mg was applied to the polyethylene disk . one patch was applied to each arm of a rhesus monkey , in a region that had been clipped one day prior to the study . the monkey was restrained during the experiment . urine samples were collected 2 , 5 , 8 , 11 , 14 , 24 , 27 , 31 , 48 , 72 and 120 hours after treatment . the patches were removed 24 hours after treatment . samples were assayed for c 14 and h 3 content by liquid scintigraphy . results from the study are presented in fig . iii and iv and show the rate of excretion of 17 - β - estradiol as a function of time . these data indicate that the polyethylene disk is an efficient system for transdermal delivery of estradiol . patches were prepared by attaching a 0 . 79cm 2 circular disk of 1 / 16 &# 34 ; thick polyethylene foam to an occlusive plastic backing . formulations were prepared , using the concentrations listed in tables 1 - 4 , and spiked with either h 3 labelled 17 - β - estradiol or h 3 labelled estrone sulfate , or , in the albuterol formulation , left unlabelled . all formulations were applied to the polyethylene patches prior to the initiation of the experiment . cadaver skin was obtained at autopsy and frozen until use , at which time it was dermatomed 250 microns thick . mouse skin was excised from freshly killed nude mice . both skins were mounted on the diffusion cell with the dermal surface towards the receiving fluid reservoir . the patches were placed on the skin so that the stratum corneum was in contact with the formulation . the receiving fluid was phosphate buffer , ph 7 . 4 , and was mechanically stirred and maintained at 32 ° c . the cadaver skin experiments ran for 48 hours , while the mouse experiments ran for 24 hours . samples of the receiving fluid were taken by an automatic sampler and analyzed for drug content by either a liquid scintillation counter ( beckman 5800 ) or hplc . results for all diffusion cells are shown in tables 1 - 4 . the steady state flux was determined by a least - squares best fit of the amount of drug diffused as a function of time , divided by the area of the patch . these data indicate that the polyethylene disk is an efficient system for transdermal delivery of 17 - β - estradiol , estrone sulfate and albuterol . table 1______________________________________transfer of 17β - estradiol across nude mouseskin from polyethylene patches drug transferred steady state fluxexperiment # ( mcg ) ( mcg / hr / cm . sup . 2 ) ______________________________________1 7 . 93 . 362 10 . 49 . 473 38 . 90 2 . 094 20 . 08 1 . 165 69 . 01 3 . 986 27 . 31 1 . 49formulation : 5 % 17 - β - estadiol 5 % menthol 90 % propylene glycol______________________________________ table 2______________________________________transfer of 17 - β - estradiol across cadaverskin from polyethylene patches drug transferred fluxexperiment # ( mcg ) ( mcg / hr / cm . sup . 2 ) ______________________________________1 4 . 74 0 . 082 7 . 63 0 . 153 15 . 85 0 . 394 17 . 23 0 . 815 6 . 73 0 . 216 29 . 33 1 . 07formulation : 5 % 17 - β - estradiol 5 % menthol 90 % propylene glycol______________________________________ table 3______________________________________transfer of estrone sulfate across cadaverskin from polyethylene patches drug transferred steady state fluxexperiment # ( mcg ) ( mcg / hr / cm . sup . 2 ) ______________________________________1 6 . 32 . 232 7 . 52 . 443 23 . 37 1 . 864 8 . 03 . 465 22 . 62 1 . 886 28 . 08 1 . 75formulation : 8 . 4 % purified conjugated estrogen concentrate , of which 17 . 9 % is estrone sulfate 62 . 7 % propylene glycol 12 . 5 % water 8 . 4 % isopropanol 8 . 0 % menthol______________________________________ table 4______________________________________transfer of albuterol across nude mouseskin from polyethylene patches drug transferred steady state fluxexperiment # ( mcg ) ( mcg / hr / cm . sup . 2 ) ______________________________________1 236 . 29 27 . 372 241 . 09 25 . 743 247 . 69 28 . 92formulation : 10 . 0 % albuterol 67 . 5 % 2 -( 2 - ethocyethoxy ) ethanol 22 . 5 % n -- methyl - 2 - pyrrolidone______________________________________
the invention provides a transdermal / transmucosal pharmaceutical delivery system having an improved drug reservoir comprising a thin layer of foamed material made from high molecular weight polyethylene , the foamed material having a void volume of at lesat 20 % per unit of surface area and a narrow pore size variation per unit of surface area .