Surgery – Controlled release therapeutic device or system – Implanted dynamic device or system
Reexamination Certificate
1999-04-08
2001-11-20
Kennedy, Sharon (Department: 3763)
Surgery
Controlled release therapeutic device or system
Implanted dynamic device or system
C604S131000, C604S181000
Reexamination Certificate
active
06319245
ABSTRACT:
The present invention relates to a drug delivery means.
In the treatment of patients it is often desirable to provide a means whereby a drug or a like agent can be introduced in a controlled manner over an extensive period of time. This is particularly the case in the treatment of patients suffering from constant pain as in the case of terminally ill patients who require a controlled delivery of an analgesic to be administered in order for them to be able to withstand the pain. In many cases it is desirable that the patient be able to administer the analgesic according to the patients needs.
In other instances it is necessary that the patient receive a drug or like agent at regular or irregular periods which in the past has required self injection by the patient or the patient's carers
In the past several devices have been proposed for controlling the introduction of a drug into the body whereby it can be delivered in a controlled manner over a period of time. Such devices have comprised pumps driven by a power source which controls the delivery of drug to the body. Some of these pumps may be mounted externally to the body and are connected to a catheter introduced to the body of the patient. Other devices have comprised a pump which is mounted subcutaneously to the body of the patient and which delivers the drug to the body at a desired location. Such devices suffer the disadvantage however that they are quite expensive and that they utilise a power source in order to effect delivery of the drug. In the event of the failure of the power source the pump must be replaced. The power source has in the past taken a variety of forms including utilisation of a phase change fluid as in the case of a device marketed under the trade mark “INFUSAID”.
The present invention comprises a development of the drug delivery means which is the subject of patent application PCT/AU94/00469 and may be mounted either externally or subcutaneously within the body of the patient and which can be controlled by the patient for the administration of a drug or like agent for the long term reduction of pain and/or the treatment of an ailment whereby the drug or agent can delivered continuously or periodically as required.
According the invention resides in a drug delivery means comprising a holding reservoir, a pumping means, a delivery reservoir and an outlet, said holding reservoir being connected to the delivery reservoir through the pump where the pump is operable manually to effect transfer of fluid from the holding reservoir to the delivery reservoir, the delivery reservoir being connected to the outlet through a flow restriction means which controls the flow to the outlet, the delivery reservoir being formed to be resiliently expandable to a maximum volume and wherein the connection between the holding reservoir and the delivery reservoir prevents pressurisation of the delivery reservoir substantially beyond a predetermined pressure which will be achieved on the delivery reservoir obtaining its maximum volume, a control means provided with the delivery reservoir to prevent further pressurisation of the delivery reservoir substantially beyond the predetermined pressure, said delivery reservoir being accommodated within the holding reservoir.
The invention may be positioned externally of the body of the patient or subcutaneously.
Other prior art delivery devices have comprised a manually operated pump which may be mounted externally to the body or subcutaneously in the body of the patient whereby the pump can be activated by the patient for the delivery of the drug as the need arises. Examples of such devices are disclosed in U.S. Pat. Nos. 4,588,394; 4,681,560; and 5,085,644 the contents of which are included herein by reference and comprise devices whereby a pumping chamber is connected via a catheter directly into the body and derives its source of drug from a holding reservoir. The pumping chambers are of the form whereby they are biased to a maximum volume condition and on activation by the patient it is moved to a minimum volume position. In the case of U.S. Pat. No. 5,085,644 the entry of drug into the pumping chamber is controlled by means of a capillary such that the pump is only able to deliver a full volume after a predetermined period of time. The disadvantage with this form of delivery means however is that the drug levels within the body will vary periodically whereby on activation of the pump the drug level within the body initially is at a high level which is then allowed to decay over a period of time until the pump is reactivated.
In addition the prior art devices do not provide for a variety of dosage regimes. For instance in some circumstances it may be desirable to provide a substantially constant dosage rate over a period of time. In other circumstances it may be desirable to provide a dosage rate which decays over a period of time from a maximum level and where with repeated activation of the device the dosage rate can be maintained at a generally constant level for an extended period of time. In other instances it may be appropriate that at each dosage occasion the volume of drug which is to be delivered may need to be varied according to the circumstances of the patient.
According to one embodiment of the invention the drug delivery means is capable of a delivery of the drug at a generally constant flow rate between dosage occasions. This is achieved in one particular form of the embodiment by providing a delivery reservoir having a high volume relative to the flow rate of the flow restriction means. According to a preferred feature of the embodiment the pressure induced on the fluid within the delivery reservoir between the dosage occasions is generally constant.
According to another embodiment of the invention the drug delivery means is capable of a delivery of the drug at a decaying flow rate between dosage occasions. This is achieved in one particular form of the embodiment by providing a delivery reservoir having a low volume relative to the flow rate of the flow restriction means.
According to a preferred feature of the invention a bacterial filter is provided between the delivery reservoir and the flow restriction means. According to one particular embodiment the filter is adapted to enable gas to separate from the liquid passing to the filter and has a gas outlet for the gas which opens into the holding reservoir. It can be a further feature of the embodiment that the filter is accommodated within the holding chamber.
According to a further preferred feature the holding reservoir is associated with a filling port.
According to a further preferred feature of the invention the pump is accommodated on or within the holding reservoir.
In one form the control means comprises a first valve between the holding reservoir and the pump and a second valve between the pump and the delivery reservoir, said first and second valves permitting unidirectional flow to the pump and delivery reservoir respectively when the delivery reservoir is not filled to its maximum volume and the pressure within the delivery reservoir is less than the predetermined pressure, the second valve permitting fluid flow back to the holding reservoir when the pressure within the delivery reservoir is at least equal to the predetermined pressure.
According to an alternative form the control means comprises a unidirectional first valve between the holding reservoir and pump and a relief chamber between the pump and the first and second valve respectively, said relief chamber being resiliently expandable with the expandable portion of the wall of the relief chamber having a higher modulus of elasticity than the expandable portion of the delivery reservoir whereby the expandable portion of the relief chamber will expand on the pressure between the pump and the first and second valve respectively being at least equal to the predetermined pressure.
In another form the control means may comprise a relief valve communicating with the delivery reservoir which will permit the flow from the delivery reservoir to t
Kennedy Sharon
Ladas & Parry
Serke Catherine
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