CA1128897A - Diffusional active agent dispenser - Google Patents
Diffusional active agent dispenserInfo
- Publication number
- CA1128897A CA1128897A CA350,350A CA350350A CA1128897A CA 1128897 A CA1128897 A CA 1128897A CA 350350 A CA350350 A CA 350350A CA 1128897 A CA1128897 A CA 1128897A
- Authority
- CA
- Canada
- Prior art keywords
- active agent
- water
- dispenser
- diffusional
- composition
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Expired
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Abstract
DIFFUSIONAL ACTIVE AGENT DISPENSER
Abstract Diffusional active agent dispensers comprising an outer microporous wall that defines an inner compartment that contains a water soluble active agent composition and an expandable member that expands when it absorbs water is disclosed. The inclusion of the expandable member in the compartment helps maintain the solution of active agent composition in a saturated state, thereby keeping the release rate of agent from the dispenser constant.
4:130:22 A-l 1/30/80
Abstract Diffusional active agent dispensers comprising an outer microporous wall that defines an inner compartment that contains a water soluble active agent composition and an expandable member that expands when it absorbs water is disclosed. The inclusion of the expandable member in the compartment helps maintain the solution of active agent composition in a saturated state, thereby keeping the release rate of agent from the dispenser constant.
4:130:22 A-l 1/30/80
Description
~Z~8~
a DIFFUSIONAL ACTIVE AGENT DISPENSER
DESCRIPTION
~5 Technical Field The invention is an improvement in active agent dispensers, particularly those in which the agent is a pharmaceutical, that
a DIFFUSIONAL ACTIVE AGENT DISPENSER
DESCRIPTION
~5 Technical Field The invention is an improvement in active agent dispensers, particularly those in which the agent is a pharmaceutical, that
2~ operate by a diffusional mecbanism in which water diffuses into the dispenser through a microporous wall and agent, in solution, diffuses out of the dispener through the microporous wall.
~ Background Art .~
The invention concerns diffusionaI active agent dispensers ~ that are intended for use in an aqueous environment and comprise ; an inner core of a water-soluble active agent composition surrounded by a coating or wall of a polymer that swells and becomes porous thereby permitting water to reach the core and dissolve the activ~ agent composition. The resulting solution of active agent di~fuses out of the dispenser througb the pores in the wall. As long as the solution is saturated with the active agent, the release rate of agent will be substantially constant. As agent i5 released from the dispenser the concentration of agent in the solution will ultimately drop below saturation. Once this occurs the release rate will ' ,;
8~7 release rate will begin to decline, following first order kinetics.
The object of the present invention is to prolong the time over which the solution of agent in the core remains saturated and thus prolong the period over which the release rate is substantially constant.
Disclosure of Invention The invention provides an active agent dispenser comprising: an outer microporous wall that surrounds and defines an inner compartment which contains a water soluble active agent composition and an expandable member, said member comprising an expandable semipermeable member that encapsulates an osmotically effective solute, a gas generating couple, or a water swellable polymer.
In operation the dispenser is placed in an aqueous environment and water from the environment diffuses through the pores of the microporous wall into the inner compartment where it dissolves the active agent composition creating a saturated solution thereof. The resulting solution diffuses through the pores out of the dispenser. Simultaneously water within the compartment is imbibed into the expandable member through the semipermeable wall of the member. The member expands in response to the imbibed water by virtue of hydrostatic pressure when the member's core is made of an osmotically effective solute, swelling when the member's core is made of a water swellable polymer, and pneumatic pressure when the member's core is made of a gas generating couple. The imbibition of water by the member reduces the water available for dissolving active agent composition and the expansion of the member reduces the volume in the compartment that is available for occupation by the solution of active agent composition. This results in saturation conditions being main-tained for a longer period.
The invention will further be described, by way of example only, with reference to the accompanying drawings.
~!r Brief Description of the Drawings In the drawings:
Figure 1 is an enlarged perspective view of a dispenser in the form of a tablet for orally admini,stering a drug to a warm blooded animal;
Figure 2 is a partly schematic, sectional view of the dispenser of Figure 1 in operation; and Figure 3 is a graph, the curves of which depict the 1 theoretical release rate of drug from the dispenser of Figure 1 versus time as compared to the theoretical release rate of drug from a prior art dispenser versus time.
Description of Specific Embodiments of the Invention , In the drawings Figures 1 and 2 depict a dispenser, generally designated 10, in the form of a tablet. Dispenser 10 is comprised of a body 11 the exterior of wbich is defined by a shape-retaining wall 12 having a plurality of pores 16 which are depicted as being circular for the purposes of illustration.
Wall 12 defines and encloses an inner compartment 13. Compartment 13 contains a water soluble drug composition 14 and an expandable member 15. Member 15 consists of an outer expandable semipermeable membrane 17 that encloses an inner core 18 of an osmotically effective solute composition, a water swellahle polymer, or a gas generating couple.
Dispenser 10 operates as follows once it is swallowed.
Water from the gastrointestinal tract diffuses through pores 16 of wall 12 into the dispenser and dissolves composition 14.
Composition 14 is shown in solution in Figure 2. Once in solution, composition 14 diffuses outwardly through pores 16
~ Background Art .~
The invention concerns diffusionaI active agent dispensers ~ that are intended for use in an aqueous environment and comprise ; an inner core of a water-soluble active agent composition surrounded by a coating or wall of a polymer that swells and becomes porous thereby permitting water to reach the core and dissolve the activ~ agent composition. The resulting solution of active agent di~fuses out of the dispenser througb the pores in the wall. As long as the solution is saturated with the active agent, the release rate of agent will be substantially constant. As agent i5 released from the dispenser the concentration of agent in the solution will ultimately drop below saturation. Once this occurs the release rate will ' ,;
8~7 release rate will begin to decline, following first order kinetics.
The object of the present invention is to prolong the time over which the solution of agent in the core remains saturated and thus prolong the period over which the release rate is substantially constant.
Disclosure of Invention The invention provides an active agent dispenser comprising: an outer microporous wall that surrounds and defines an inner compartment which contains a water soluble active agent composition and an expandable member, said member comprising an expandable semipermeable member that encapsulates an osmotically effective solute, a gas generating couple, or a water swellable polymer.
In operation the dispenser is placed in an aqueous environment and water from the environment diffuses through the pores of the microporous wall into the inner compartment where it dissolves the active agent composition creating a saturated solution thereof. The resulting solution diffuses through the pores out of the dispenser. Simultaneously water within the compartment is imbibed into the expandable member through the semipermeable wall of the member. The member expands in response to the imbibed water by virtue of hydrostatic pressure when the member's core is made of an osmotically effective solute, swelling when the member's core is made of a water swellable polymer, and pneumatic pressure when the member's core is made of a gas generating couple. The imbibition of water by the member reduces the water available for dissolving active agent composition and the expansion of the member reduces the volume in the compartment that is available for occupation by the solution of active agent composition. This results in saturation conditions being main-tained for a longer period.
The invention will further be described, by way of example only, with reference to the accompanying drawings.
~!r Brief Description of the Drawings In the drawings:
Figure 1 is an enlarged perspective view of a dispenser in the form of a tablet for orally admini,stering a drug to a warm blooded animal;
Figure 2 is a partly schematic, sectional view of the dispenser of Figure 1 in operation; and Figure 3 is a graph, the curves of which depict the 1 theoretical release rate of drug from the dispenser of Figure 1 versus time as compared to the theoretical release rate of drug from a prior art dispenser versus time.
Description of Specific Embodiments of the Invention , In the drawings Figures 1 and 2 depict a dispenser, generally designated 10, in the form of a tablet. Dispenser 10 is comprised of a body 11 the exterior of wbich is defined by a shape-retaining wall 12 having a plurality of pores 16 which are depicted as being circular for the purposes of illustration.
Wall 12 defines and encloses an inner compartment 13. Compartment 13 contains a water soluble drug composition 14 and an expandable member 15. Member 15 consists of an outer expandable semipermeable membrane 17 that encloses an inner core 18 of an osmotically effective solute composition, a water swellahle polymer, or a gas generating couple.
Dispenser 10 operates as follows once it is swallowed.
Water from the gastrointestinal tract diffuses through pores 16 of wall 12 into the dispenser and dissolves composition 14.
Composition 14 is shown in solution in Figure 2. Once in solution, composition 14 diffuses outwardly through pores 16
3 into the gastrointestinal tract. Also, once water is present in the dispenser, member 15 becomes activated. Water from the solution of composition 14 diffuses through semipermeable membrane 17 and reaches core 1~. If core 18 is composed of an osmotically effective solute the water dissolves the solute and 3j an osmotic pressure gradient is established across membrane 17 between the solution of composition 14 and the solute solution.
This causes more water to be imbibed through membrane 17 into
This causes more water to be imbibed through membrane 17 into
-4~ 7 member 15. The resulting hydraulic pressure causes member 15 to expand. If core 18 is composed of a water swellable polymer, the water swells tbe polymer thus causing member 15 to expand.
If core 18 is composed of a gas generating couple, the water causes the couple to react and generate gas. The resulting pneumatic pressure causes member 15 to expand. As member 15 absorbs water, it reduces the water content of the solution of composition 14. And, as member 15 expands, it reduces the volume witbin compartment 13 tbat may be occupied by the solution of composition 14. Tbe net result of tbis combined action is to keep the colution of composition 14 saturated and tbus at unit activity.
Figure 3 illustrates the release rate of drug versus time from the dispenser of Figure 1 (dasbed line DEF) as lS compa~ed to a similar dispenser tbat does not include an expanding member 15 (solid line ABC). As shown tbe constancy of release rate is prolonged from time B to time E and the decline from constancy to exhaustion is much more rapid in the case of the dispenser of Figure 1.
The microporous material from which wall 12 is made has ~2~ a plurality of microscopic interconnected pores or voids when the dispenser is in operation. The pores generally constitute
If core 18 is composed of a gas generating couple, the water causes the couple to react and generate gas. The resulting pneumatic pressure causes member 15 to expand. As member 15 absorbs water, it reduces the water content of the solution of composition 14. And, as member 15 expands, it reduces the volume witbin compartment 13 tbat may be occupied by the solution of composition 14. Tbe net result of tbis combined action is to keep the colution of composition 14 saturated and tbus at unit activity.
Figure 3 illustrates the release rate of drug versus time from the dispenser of Figure 1 (dasbed line DEF) as lS compa~ed to a similar dispenser tbat does not include an expanding member 15 (solid line ABC). As shown tbe constancy of release rate is prolonged from time B to time E and the decline from constancy to exhaustion is much more rapid in the case of the dispenser of Figure 1.
The microporous material from which wall 12 is made has ~2~ a plurality of microscopic interconnected pores or voids when the dispenser is in operation. The pores generally constitute
5% to 95% of the volume of the material and have sizes in the range of 50 angstroms and 100 microns. The pores may be preformed in the material or formed in situ in the gastrointestinal tract. The polymers that may be used to make such materials and the techniques for forming the pores are well known.
Examples of techniques for preforming the pores are etching a polymer by nuclear tracking, cooling a polymer solution to form solvent crystals in the polymer followed by curing the polymer to remove the crystals, stretching polymer films, and leaching 3 soluble components from a polymer. The pores may be formed in situ by using a polymer that swells and becomes porous or that includes a water soluble pore-forming component that is dissolved or leached form the polymer to create pores therein.
Examples of polymers that may be used for wall 12 are described in U.S. Patent No. 4,160,452.
The semipermeable polymers that may be used to make membrane 17 are permeable to water and substantially impermeable to the other contents of compartment 13 and member 15. Examples of such polymers are cellulose acetate, cellulose diacetate, cellulose triacetate, dimethyl cellulose acetate, cellulose acetate ethyl carbamate, and the other cellulose ethers and esters. In order to impart flexibility and expandability to membrane 17 it may be desirable to add one or more plasticizers to the semipermeable polymer. Examples of such plasticizers are dimethyl phthalate, dipropyl phthalate, di(2-ethylhexyl)-phthalate, di-isopropyl phthalate, diamyl phthalate and dicapryl 0 phthalate; alkyl and aryl phosphates such as tributyl phosphate, trioctyl phosphate, tricresyl phosphate, and triphenyl phosphate;
alkyl citrate and citrates esters such as tributyl citrate, triethyl citrate, and acetyl triethylcitrate; alkyl adipates such as dioctyl adipate, diethyl adipate, and di(2-methoxyethyl)-adipate; dialkyl tartrates such as diethyl tartrate and dibutyl ~5 tartrate; alkyl sebacates such as diethyl sebacate, dipropyl sebacate and dinonyl sebacate; alkyl succinates such as diethyl succinate and dibutyl succinate; alkyl glycolates, alkyl glycerolates, glycol esters and glycerols esters such as glycerol diacetate, glycerol triacetate, glycerol monolactate 2~ diacetate, methyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate, ethylene glycol diacetate, ethylene glycol diabutyrate, triethylene glycol diacetate, triethylene glycol dibutyrate and triethylene glycol dipropionate.
Osmotically effective solutes that may be used in member 15 includes organic and inorganic compounds that exhibit high osmotic pressures in solution. Such solutes include magnesium sulfate, magnesium chloride, sodium chloride, lithium chloride, potassium sulfate, sodium carbonate, potassium acid phosphate, mannitol, urea, sucrose, and the like. Other osmotically effective solutes are disclosed in l].S. Patents Nos. 3,854,770 3 and 4,077,407.
Swellable polymers that may be used in member 15 are the lightly cross-linked hydrophilic hydrogels that swell in the presence of water to a high degree without dissolution, usually exhibiting a 5 to 50 fold volume increase. Exemplary hydrogels include poly(hydroxyalkyl methacrylates), poly(acrylamide), poly(methacrylamide), poly(N-vinyl-2-pyrrolidone), anionic and cationic hydrogels, polyelectrolyte complexes, a
Examples of techniques for preforming the pores are etching a polymer by nuclear tracking, cooling a polymer solution to form solvent crystals in the polymer followed by curing the polymer to remove the crystals, stretching polymer films, and leaching 3 soluble components from a polymer. The pores may be formed in situ by using a polymer that swells and becomes porous or that includes a water soluble pore-forming component that is dissolved or leached form the polymer to create pores therein.
Examples of polymers that may be used for wall 12 are described in U.S. Patent No. 4,160,452.
The semipermeable polymers that may be used to make membrane 17 are permeable to water and substantially impermeable to the other contents of compartment 13 and member 15. Examples of such polymers are cellulose acetate, cellulose diacetate, cellulose triacetate, dimethyl cellulose acetate, cellulose acetate ethyl carbamate, and the other cellulose ethers and esters. In order to impart flexibility and expandability to membrane 17 it may be desirable to add one or more plasticizers to the semipermeable polymer. Examples of such plasticizers are dimethyl phthalate, dipropyl phthalate, di(2-ethylhexyl)-phthalate, di-isopropyl phthalate, diamyl phthalate and dicapryl 0 phthalate; alkyl and aryl phosphates such as tributyl phosphate, trioctyl phosphate, tricresyl phosphate, and triphenyl phosphate;
alkyl citrate and citrates esters such as tributyl citrate, triethyl citrate, and acetyl triethylcitrate; alkyl adipates such as dioctyl adipate, diethyl adipate, and di(2-methoxyethyl)-adipate; dialkyl tartrates such as diethyl tartrate and dibutyl ~5 tartrate; alkyl sebacates such as diethyl sebacate, dipropyl sebacate and dinonyl sebacate; alkyl succinates such as diethyl succinate and dibutyl succinate; alkyl glycolates, alkyl glycerolates, glycol esters and glycerols esters such as glycerol diacetate, glycerol triacetate, glycerol monolactate 2~ diacetate, methyl phthalyl ethyl glycolate, butyl phthalyl butyl glycolate, ethylene glycol diacetate, ethylene glycol diabutyrate, triethylene glycol diacetate, triethylene glycol dibutyrate and triethylene glycol dipropionate.
Osmotically effective solutes that may be used in member 15 includes organic and inorganic compounds that exhibit high osmotic pressures in solution. Such solutes include magnesium sulfate, magnesium chloride, sodium chloride, lithium chloride, potassium sulfate, sodium carbonate, potassium acid phosphate, mannitol, urea, sucrose, and the like. Other osmotically effective solutes are disclosed in l].S. Patents Nos. 3,854,770 3 and 4,077,407.
Swellable polymers that may be used in member 15 are the lightly cross-linked hydrophilic hydrogels that swell in the presence of water to a high degree without dissolution, usually exhibiting a 5 to 50 fold volume increase. Exemplary hydrogels include poly(hydroxyalkyl methacrylates), poly(acrylamide), poly(methacrylamide), poly(N-vinyl-2-pyrrolidone), anionic and cationic hydrogels, polyelectrolyte complexes, a
-6~
water-insoluble, water-swellable copolymer produced ~y forming a dispersion of finely divided copolymers of maleic anhydride with styrene, ethylene, propylene, butylene or isobutylene cross-linked with from about 0~001 to about 0.5 moles of a polyunsaturated cross-linking a8ent per mole of maleic anhydride in the copolymer, the water-swellable polymers of N-vinyl lactams, semi-solid cross-linked poly(vinyl pyrrolidone), diester cross-linked polyglucan hydrogels and anionic hydrogels of heterocyclic N-vinyl monomers.
The gas generating couples that may be used in member 15 comprise a solid acid compound and a basic compound that dissolve and react in the presence of water to produce carbon dioxide. The acid compounds include organic acids such as malic, fumaric, tartaric, itaconic, maleic, citric, adipic, lS succinic and mesaconic, and inorganic acids such as sulfamic or phoæphoric, also acid salts sucb as monosodium citrate, potassium acid tartrate and potassium bitartrate. The basic compounds include metal carbonates and bicarbonates, such as alkali metal carbonates and bicarbonates. Exemplary materials include ; lithium, sodium, and potassium carbonates and bicarbonates, and 2~ the alkaline earth compounds magnesium and calcium carbonates and bicarbonates. The acid and base of the couple are preferably in ~ubstantially stoichiometric proportions.
The dispensers may be manufactured according to standard procedures. For example member 15 is first made by encapsulating an osmotic solute, gas generating couple, or swellable polymer with a semipermeable polymer film, and then the water soluble active agent composition 14 is coated or pressed about member 15. Wall 12 is then applied to the resulting subassembly by molding, spraying, air suspension or dipping. In another procedure wall 12 is first cast and then shaped into an open container which is then filled with active agent composition 14 and member 15, and then closed and sealed.
The following examples further illustrate the invention.
They are not intened to limit the scope of the invention in any way. Unless indicated otherwise, percentages and proportions are by weight.
:
water-insoluble, water-swellable copolymer produced ~y forming a dispersion of finely divided copolymers of maleic anhydride with styrene, ethylene, propylene, butylene or isobutylene cross-linked with from about 0~001 to about 0.5 moles of a polyunsaturated cross-linking a8ent per mole of maleic anhydride in the copolymer, the water-swellable polymers of N-vinyl lactams, semi-solid cross-linked poly(vinyl pyrrolidone), diester cross-linked polyglucan hydrogels and anionic hydrogels of heterocyclic N-vinyl monomers.
The gas generating couples that may be used in member 15 comprise a solid acid compound and a basic compound that dissolve and react in the presence of water to produce carbon dioxide. The acid compounds include organic acids such as malic, fumaric, tartaric, itaconic, maleic, citric, adipic, lS succinic and mesaconic, and inorganic acids such as sulfamic or phoæphoric, also acid salts sucb as monosodium citrate, potassium acid tartrate and potassium bitartrate. The basic compounds include metal carbonates and bicarbonates, such as alkali metal carbonates and bicarbonates. Exemplary materials include ; lithium, sodium, and potassium carbonates and bicarbonates, and 2~ the alkaline earth compounds magnesium and calcium carbonates and bicarbonates. The acid and base of the couple are preferably in ~ubstantially stoichiometric proportions.
The dispensers may be manufactured according to standard procedures. For example member 15 is first made by encapsulating an osmotic solute, gas generating couple, or swellable polymer with a semipermeable polymer film, and then the water soluble active agent composition 14 is coated or pressed about member 15. Wall 12 is then applied to the resulting subassembly by molding, spraying, air suspension or dipping. In another procedure wall 12 is first cast and then shaped into an open container which is then filled with active agent composition 14 and member 15, and then closed and sealed.
The following examples further illustrate the invention.
They are not intened to limit the scope of the invention in any way. Unless indicated otherwise, percentages and proportions are by weight.
:
-7~ 7 Example 1 First, an expandable member is manufactured by compressing 125 mg of sodium chloride and then coating the pressed sodium chloride in a~ air suspension machine with a composition comprising 70% cellulose acetate having an acetyl content of 32% mixed with 30% polyethylene glycol having a molecular weight of 400 dissolved in methylene chloride-methanol, 80:20 by volume, until an expandable film is formed on the 1~ member.
Next, 235 mg of dry procainamide is mixed with the member and the mixture is compressed. This compressed mix is then coated in an air suspension machine with a composition consisting of 65 g of celluIose acetate having an acetyl content of 32%, 41 g of hexane hexol, 11.7 g of polyethylene glycol 400, and solvent consisting of 19 ml of acetone and 375 ml of water.
The coating is 175 microns thick.
Example 2 First, an expandable member is made by pressing a mixture of 56.7% potassium hydrogen carbonate, 40.2% citric acid and 3% anhydrous magnesium silicate, and then coating the mixute in an air suspension macbine with a film consisting of 90% cellulose acetate having an acetyl content of 32% having homogenously dispersed therein 10% by weight of polyethylene glycol having a molecular weight of 400. The coating process is carried out with a solvent consisting of methylene chloride-methanol, 80:20, by volume.
Next, the member is surrounded with 500 mg of potassium chloride, by compression, in a'Manesty machine, and a microporous wall of poly(vinyl cbloride) is prepared by leaching a sheet of polymer consisting the poly(vinyl chloride) containing the pore forming agent poly[p-dimethylamino-styrene]. The wall is formed by cas,ting from a cyclohexane solution and the solvent evaporated. Then, an aqueous acidic solution of hydrochloric acid is used to leach the pore formers and yield the microporous wall. Tbe leaching is carried out at room tempera~ure followed by washing with distilled water to remove the acid.
Next, 235 mg of dry procainamide is mixed with the member and the mixture is compressed. This compressed mix is then coated in an air suspension machine with a composition consisting of 65 g of celluIose acetate having an acetyl content of 32%, 41 g of hexane hexol, 11.7 g of polyethylene glycol 400, and solvent consisting of 19 ml of acetone and 375 ml of water.
The coating is 175 microns thick.
Example 2 First, an expandable member is made by pressing a mixture of 56.7% potassium hydrogen carbonate, 40.2% citric acid and 3% anhydrous magnesium silicate, and then coating the mixute in an air suspension macbine with a film consisting of 90% cellulose acetate having an acetyl content of 32% having homogenously dispersed therein 10% by weight of polyethylene glycol having a molecular weight of 400. The coating process is carried out with a solvent consisting of methylene chloride-methanol, 80:20, by volume.
Next, the member is surrounded with 500 mg of potassium chloride, by compression, in a'Manesty machine, and a microporous wall of poly(vinyl cbloride) is prepared by leaching a sheet of polymer consisting the poly(vinyl chloride) containing the pore forming agent poly[p-dimethylamino-styrene]. The wall is formed by cas,ting from a cyclohexane solution and the solvent evaporated. Then, an aqueous acidic solution of hydrochloric acid is used to leach the pore formers and yield the microporous wall. Tbe leaching is carried out at room tempera~ure followed by washing with distilled water to remove the acid.
-8 Examele 3 A dispenser in the form of a tablet for administering procainamide hydrochloride to the gastrointestinal tract of a warm~blooded animal i9 made as follows: first, 200 mg of lightly cross-linked, swellable poly(hydroxyalkyl) methacrylate is coated in an air suspension machine with a composition comprising 70% cellulose acetate having an acetyl content of 32% mixed with 30% of polyethylene glycol having a molecular weight of 400 dissolved in methylene chloride-methanol, 80:20 by volume, until the polymer is encapsulated. Next, 235 mg of procainamide hydrochloride is pressed into a solid mass having ~ a shape corresponding to the shape of member 15 and joined `15 thereto by spreading a drop of liquified cellulose acetate between their interfaces. Then, the resulting subassembly is surrounded with a wall of a microporous poly~eric polypropylene having a void volume of 0.565 to 0.075 cm3/gm, a density of 0.60 to 0.85 gm/cm3, and a pore size of 150 to 5000 angstroms.
While only dispersers in which the active agent is drug 2~ bave been described above it will be appreciated ~hat embodiments containing other active agents such as agricultural chemicals and water treatment chemicals may be made.
While only dispersers in which the active agent is drug 2~ bave been described above it will be appreciated ~hat embodiments containing other active agents such as agricultural chemicals and water treatment chemicals may be made.
Claims
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:
1. An active agent dispenser comprising: an outer microporous wall that surrounds and defines an inner compartment which contains a water soluble active agent composition and an expandable member, said member compris-ing an expandable semipermeable member that encapsulates an osmotically effec-tive solute, a gas generating couple, or a water swellable polymer.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA350,350A CA1128897A (en) | 1980-04-22 | 1980-04-22 | Diffusional active agent dispenser |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CA350,350A CA1128897A (en) | 1980-04-22 | 1980-04-22 | Diffusional active agent dispenser |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1128897A true CA1128897A (en) | 1982-08-03 |
Family
ID=4116755
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA350,350A Expired CA1128897A (en) | 1980-04-22 | 1980-04-22 | Diffusional active agent dispenser |
Country Status (1)
| Country | Link |
|---|---|
| CA (1) | CA1128897A (en) |
-
1980
- 1980-04-22 CA CA350,350A patent/CA1128897A/en not_active Expired
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