Gas driven dispensing device and gas generating engine therefor

A fluid driven dispensing device for delivering an agent into an environment of use at a substantially constant rate over a substantial portion of a predetermined agent administration period, the device comprising:

• (a) a syringe having a moveable piston, the piston dividing the syringe into an agent compartment and a driving compartment said agent compartment having outlet means communicating with the environment of use;
• (b) a reservoir fluid in said driving compartment and comprising a material selected from the group consisting of an aqueous basic fluid, an aqueous acidic fluid and water;
• and
• (c) a gas generating engine disposed within the driving compartment, the gas generating engine comprising:
• (i) a material selected from the group consisting of, respectively, a solid acidic composition, a solid basic composition an a mixture of a solid acidic and a solid basic composition;
• and
• (ii) means for maintaining the surface area of the solid composition exposed to the reservoir fluid substantially constant over said substantial portion of said administration period;
• wherein in operation, the agent is delivered from the device by reacting the solid composition with the reservoir fluid to generate a gas in the driving compartment which exerts pressure on the piston to deliver the agent from the agent compartment to the environment of use.

A fluid driven dispensing device for delivering an agent into an environment of use at a substantially constant rate over a substantial portion of a predetermined agent administration period, the device comprising:

• (a) housing means;
• (b) piston means slidably received within the housing means, the piston means having first and second ends, the first end having a cross-sectional area greater than the second end;
• (c) an agent compartment formed between the housing means and the second end of the piston means and having agent outlet means communicating with the environment of use;
• d) a driving compartment formed between the housing means and the second end of the piston means;
• (e) a reservoir fluid in said driving compartment and comprising a material selected from the group consisting of an aqueous basic fluid, an aqueous acidic fluid and water;
• and
• (f) a gas generating engine within the driving compartment actuateable by the reservoir fluid, the gas generating engine comprising:
• (i) a material selected from the group consisting of, respectively, a solid acidic composition, a solid basic composition and a mixture of a solid acidic and a solid basic composition;
• and
• (ii) means for maintaining the surface area of the solid composition exposed to the reservoir fluid substantially constant over said substantial portion of said administration period;
• whereby a given volume of gas delivered to the driving compartment from the engine means will dispense a larger volume of agent from the agent compartment.

A fluid driven dispensing device for delivering a beneficial agent to an environment of use at a substantially constant rate over a substantial portion of a predetermined agent administration period, the device comprising:

• a) a syringe housing adapted to contain the agent and having outlet means proximate one end thereof;
• b) an amplication housing attached at one end to the other end of the syringe housing;
• c) a driving housing attached to the other end of the amplification housing adapted to contain a reservoir fluid;
• d) piston means slidably received within the syringe housing and the amplification housing, the end of the piston means within the syringe housing comprising plunger means having a larger cross-sectional area than the end of the piston proximate the driving housing, the piston means being movable from a first position proximate the amplification housing end of the syringe housing to a second position proximate the outlet means;
• e) a reservoir fluid comprising a material selected from the group consisting of an aqueous basic fluid, an aqueous acidic fluid and water within the driving housing;
• and
• (f) a gas generating engine within the driving compartment actuateable by the reservoir fluid and in gas communicating relationship with the piston means, the gas generating means comprising:
• (i) a material selected from the group consisting of, respectively, a solid acidic composition, a solid basic composition and a mixture of a solid acidic and a solid basic composition;
• and
• (ii) means for maintaining the surface area of the sollid composition exposed to the reservoir fluid substantially constant over said substantial portion of said administration period;
• whereby a given volume of gas delivered to the piston means from the gas generating engine will dispense a larger volume of an agent from the syringe housing.

In a fluid driven agent dispensing device comprising:

• piston means having first and second ends;
• and
• housing means slideably receiving the piston means, the first end of the housing forming an agent dispensing compartment having outlet means through which an agent may be displaced by movement of the first end of the piston, the second end of the housing being adapted to maintain a gas generating engine in discharging relationship to the second end of the piston and to contain a reservoir fluid for the engine fluid for the engine;
• the improvement, whereby the a small volume of gas can dispense a larger volume of agent at a substantially constant rate over a substantial portion of a predetermined administration period, which comprises:
• a) the cross-sectional area of the first end of the piston is at least 1.5 times the cross-sectional area of the second end;
• b) the reservoir fluid is a material selected from the group consisting of an aqueous basic fluid, an aqueous acidic fluid and water;
• and
• c) the gas generating engine comprises:
• (i) a material selected from the group consisting of, respectively, a solid acidic composition, a solid basic composition and a mixture of a solid acidic and a solid basic composition;
• and
• (ii) means for maintaining the surface area of the solid composition exposed to the reservoir fluid substantially constant over said substantial portion of said administration period.