Delivery system

Claim 1

ILIL i-LIIIIIIII 4. A device according to claims 1 or 2 wherein said porous material is selected from a first group consisting of sintered poly(ethylene), sintered poly-(propylene), sintered poly(tetrafluoroethylene), sintered poly(vinyl chloride) or sintered polystyrene; and a second group consisting of a porous fabric material selected from poly(ethylene), poly(propy- lene), poly(tetrafluoroethylene), glass or modacrylic. A device according to any of claims 1 to 4, wherein said aqueous liquid-containing environment is the rumeno-recticular sac of a ruminant animal. 6. A device according to claim 5 wherein the hydrogel so medium is gelled cellulose triacetate. 7. A device according to claim 6 wherein the chemical is an anthelmintic agent. 8. A device according to claim 7 wherein the anthel- mintic agent is a water soluble acid addition salt of levamisole, S pyrantel or morantel. 9. A device according to claim 8 wherein the water soluble acid addition salt of morantel is the tartrate. 10. Process for production of a device according to O. claim 1 for the controlled and continuous release of a chemical to an aqueous liquid-containing environment over a prolonged period of time characterized in that a chemical is enclosed in a reservoir surrounded by a shaped wall formed in part at least of a porous material, said porous material being in contact with at least a part of said reservoir, the pores of said porous material being impregnated with a hydrogel medium, said hydrogel medium means having channels or pores which permit the diffusion of aqueous liquid from said environment into said reservoir to form a solution of said chemical in said aqueous liquid; and permit the diffusion of said solution containing said chemical to said environment, so that said device when placed in said environment continuously releases said chemical from said reservoir to said environment at a physiologically effective controlled rate, the dissolved chemical so released being replaced by the continuous dissolving of said chemical in said reservoir, the amount of dissolved chemical in said reservoir changing continuously throughout said prolonged tinii. period, so as to maintain the rate of chem- ical release to said environment substantially constant during S. a substantial portion of said prolonged time period. 11. Process as claimed in claim 0 characterized in that the porous material is sintered poly(ethylene), sintered poly(propylene), sintered poly(tetrafluoro-ethylene), sintered poly(vinyl chloride) or sintered polystyrene. 12. Process according to claim 11, characterized by production of a device to be placed in the rumeno-reticular sac of a ruminant animal, the chemical being an anthelmintic agent. .13. Process according to any of claims 11 to 12, characterized in that the hydrogel medium is gelled cellulose 1. triacetate. 14. Process according to claim 13, characterized in that the chemical is water soluble salt of levamisole, pyrantel or morantel. Process according to claim 14, characterized in that the water soluble acid addition salt of morantel is the tartrate. 4 56 DATED this THIRTIETH day of OCTOBER, 1980 PFIZER INC. Patent Attorneys for the Applicant SPRUSON FERGUSON 9 *5 9. S a. a. 4SS S. a. S *559 deSS S *5S* S S SS 55 9 a a.. S