referring to the figures for a better understanding of the invention , it will be appreciated that a chemically crosslinked hydrogel will remain solid and in gel form as long as the water content is retained , therefore it is desirable to enclose the hydrogel 11 within a removable container such as a peelable release paper 12 as shown in fig1 and 2 . it will be appreciated that the hydrogel 11 can be formed and packaged in this manner by conventional methods such as passing the plastic hydrogel 11 through a set of forming rollers with strips of release paper 12 on either side . likewise the gel can be cured in molds of various shapes and sizes and individually packaged . the crosslinked hydrogels 11 thus formed and in accordance with my invention include a medicant as an active ingredient which when placed into contact with the skin of a patient will be received into the patient &# 39 ; s system via transdermal transport . the preferred active ingredients are lidocainehydrochloride , hydrocortisone , menthol , and methyl salicylate , although other well - known ingredients used in topical applications may be useful . in fig3 and 4 , the hydrogel is formed with a scrim 13 contained internally , the scrim 13 may be gauze or a paper towel and serves to strengthen the hydrogel . in each of my hydrogels , i have utilized aluminum acetate as the crosslinking and ionization agent , however each active ingredient requires a somewhat different formulation as shown in the tables below . it should be understood that is is difficult to achieve the desired stabilization of the hydrogels in that if they are excessively crosslinked , the product tends to decompose , while under - crosslinking leaves the product too fluid . table i______________________________________lidocainehydrochloride formulation # 1______________________________________100 cc water1 . 4 g carboxymethylcellulose2 . 0 g lidocainehydrochloride7 . 2 g gelatin3 . 0 g polyethylene glycol0 . 17 g aluminum acetate______________________________________ table ii______________________________________lidocainehydrochloride formulation # 2______________________________________100 cc water1 . 4 g carboxymethylcellulose2 . 0 g lidocainehydrochloride3 . 0 g polyethylene glycol0 . 7 g menthol0 . 17 g aluminum acetate______________________________________ table iii______________________________________limits on lidocainehydrochloride formulation / 100 cc water______________________________________1 . 2 to 1 . 7 g carboxymethylcelluloseup to 4 . 0 g lidocainehydrochloride0 . 0 to 8 . 0 g gelatin0 . 0 to 6 . 0 g polyethylene glycol0 . 0 to 2 . 0 g menthol0 . 17 to 0 . 50 g aluminum acetate______________________________________ table iv______________________________________hydrocortisone formulation______________________________________100 cc water1 . 4 g carboxymethylcellulose0 . 5 g hydrocortisone3 . 2 g polyethylene glycol1 . 0 g menthol0 . 16 g lanolin0 . 17 g aluminum acetate______________________________________ table v______________________________________limits on hydrocortisone formulation / 100 cc water______________________________________1 . 1 to 1 . 6 g carboxymethylcelluloseup to 0 . 5 g hydrocortisone2 . 0 to 5 . 0 g polyethylene glycol0 . 0 to 5 . 0 g menthol0 . 0 to 1 . 0 g lanolin0 . 17 to 0 . 50 g aluminum acetate______________________________________ table vi______________________________________methyl salicylate formulation______________________________________100 g water1 . 4 g carboxymethycellulose6 . 67 g methyl salicylate1 . 32 g menthol2 . 7 g polyethylene glycol0 . 14 g lanolin0 . 2 g aluminum acetate______________________________________ table vii______________________________________limits on methyl salicylate formulation / 100 cc water______________________________________1 . 2 to 1 . 6 g carboxymethylcellulose3 . 0 to 8 . 0 g methyl salicylate0 . 5 to 5 . 0 g menthol2 . 0 to 3 . 5 g polyethylene glycol0 . 0 to 2 . 2 g lanolin0 . 20 to 0 . 50 g aluminum acetate______________________________________ as may be seen from the tables , the chemicals used in each formulation are readily commercially available from a variety of sources . to produce any one of the formulations all of the ingredients listed in the specific tables , e . g . table iv , except the crosslinking agent , aluminum acetate , are mixed at once and heated at about 160 degrees fahrenheit for one hour . the solution is then cooled to below 120 degrees , whereupon the required amount of aluminum acetate is added . the solution may then be fabricated into any of the products shown in fig1 - 6 . for example , solid discs , rectangles or squares may be made by pouring the solution into appropriately shaped molds to the desired thickness . electrodes , such as shown in fig5 and 6 , may be made by spraying or painting the solution on a conductive carbon or silicon electrode 14 which can provide electrical connection for tens or iontophoresis treatment . or the hydrogel may be painted or sprayed onto a scrim 13 , or fed through rollers together with the release paper and scrim , which permits the fabrication of thinner hydrogels due to the structural support of the scrim . the curing time for crosslinking of the hydrogel is from about four to about twenty - four hours at room temperature . while i have shown my invention in various forms , it will be obvious to those skilled in the art that it is not so limited but is susceptible of various changes and modifications without departing from the spirit thereof .
a chemically crosslinked hydrogel includes an active ingredient for transdermal transport selected from the group of lidocainehydrochloride , hydrocortisone , menthol , and methyl salicylate and utilizes as a crosslinking agent an aluminum acetate , which is a polyvalent salt , which renders the resulting hydrogel electrically conductive with a resistance of less than 10 , 000 ohms per linear centimeter .