Mems device and method for delivery of therapeutic agents

Abstract

Embodiments of an implantable device for delivering a therapeutic agent to a patient include a reservoir configured to contain a liquid comprising the therapeutic agent, and a cannula in fluid communication with the reservoir. A valve for maintaining a constant flow rate through the cannula independent of the pressure applied to the device may be included.

1 . An implantable device for delivering a therapeutic agent to a patient, the device comprising:
 a reservoir for a liquid;   a cannula in fluid communication with the reservoir, the cannula having an outlet configured for fluid communication with the patient; and   a valve for maintaining a constant flow rate through the cannula independent of pressure applied to the device.   
     
     
         2 . The device of  claim 1  wherein the reservoir comprises a first wall puncturable by a needle to facilitate refilling of the reservoir. 
     
     
         3 . The device of  claim 2  wherein the first wall reseals itself upon removal of the needle. 
     
     
         4 . The device of  claim 2  wherein the reservoir further comprises a second wall which is generally unpuncturable by the needle. 
     
     
         5 . The device of  claim 1  wherein the cannula outlet is insertable into the patient. 
     
     
         6 . The device of  claim 1  wherein the valve is at the end of the cannula. 
     
     
         7 . The device of  claim 1  wherein the cannula is parylene. 
     
     
         8 . The device of  claim 1 , further comprising:
 first and second electrodes and circuitry for activating the electrodes; and   a flexible membrane disposed above the electrodes and defining a wall of the reservoir, the membrane being configured to expand and contract with increases and decreases in pressure, activation of the electrodes causing creation of a gas to thereby expand the membrane so that liquid is forced from the reservoir into the cannula.   
     
     
         9 . The device of  claim 8  wherein the membrane has a series of corrugations facilitating expansion and contraction thereof. 
     
     
         9 . A method of delivering a therapeutic agent to a patient from a drug pump implanted in the patient, the drug pump comprising a reservoir and a cannula, the method comprising the steps of:
 pumping a therapeutic liquid to a body site from the reservoir through the cannula; and   maintaining a constant flow rate of the liquid through the cannula independent of the pressure applied to the drug pump.   
     
     
         10 . The method of  claim 9 , wherein the reservoir comprises a first wall, and further comprising the step of puncturing the first wall by a needle to facilitate refilling of the reservoir, the first wall resealing itself upon removal of the needle. 
     
     
         11 . The method of  claim 9 , wherein the constant flow is maintained by a valve. 
     
     
         12 . The method of  claim 11 , wherein the valve is disposed at the end of the cannula.