Surgery – Means for introducing or removing material from body for... – Treating material introduced into or removed from body...
Reexamination Certificate
1998-03-13
2003-08-12
Hayes, Michael J. (Department: 3763)
Surgery
Means for introducing or removing material from body for...
Treating material introduced into or removed from body...
C222S321200
Reexamination Certificate
active
06605060
ABSTRACT:
TECHNICAL FIELD
The present invention relates to an improved apparatus for effecting patient-controlled infusion of medicaments and is particularly applicable to the delivery of medicaments which may be absorbed across dermal and mucosal surfaces such as the respiratory tract, the nasal mucosa, the sublingual area, the ocular surface, intravaginal mucosa or intrarectal mucosa.
BACKGROUND ART
It has been recognised for some time that patient controlled medicament delivery (PCDD) as in the case of patient controlled analgesia (PCA) is desirable in many situations. Before the advent of patient controlled medicament delivery, therapeutic treatments relied upon periodic injections of medicaments such as natural and synthetic opioids by a physician or nurse. This has the disadvantage that for most of the time the patient's medicament level may be significantly above or below the optimum.
PCDD improved on the prior art by enabling the infusion of small quantities of medicaments at regular intervals as perceived to be required by the patient. However, to date PCDD has been effected by sophisticated electronic pump systems which have a number of disadvantages:
(a) They are expensive;
(b) They are complex and require skilled maintenance; and
(c) They are capable of administering an overdose as a result of machine failure or of operator error in setting up; a number of deaths from this cause have been reported.
Recently mechanical PCDD pumping systems have been developed to ameliorate some of the disadvantages attendant with prior art devices. Such devices generally consists of a reservoir and a pumping assembly that contains a dose chamber which takes a predetermined amount of time to fill. These pumps have the disadvantage that filling of the dose chamber in the pumping assembly may take a long time and filling of the last portion of the dose chamber may be extremely slow. Moreover, if patients activate mechanical PCDD pumping systems prior to complete filling of the fluid dose chamber they may receive an excess of medicament. Thus, physicians may have no means of controlling the total amount of medicament delivered to a patient, leading to possible medicament overdosing by the patient.
Physicians generally associate the term “lockout” with a period of delay between medicament deliveries. They also have an expectation that the dose chamber in the delivery device will be 100% full at the end of each lockout period.
The filling cycle of electronic PCDD pumps is generally immediate. Electronic pumps allow a unit dose of medicament to be delivered and control a time interval where no further doses of medicament can be delivered. When this time interval is completed the patient can activate a switch which indicates his/her desire for another dose. The next unit dose will then be delivered and the next lockout will take effect.
In mechanical PCDD pumps the filling time of the dose chamber is progressive over a period of time which is equivalent to the predetermined lockout period. Typically, a concave filling curve is observed wherein the majority of the dose chamber fills rapidly after medicament delivery/release after which there is a slow and progressive filling of the last portion of the dose chamber. Often the filling time which leads to 100% filling of the dose chamber in such pumps is greater than the lockout period. Thus, a patient who activates the device prior to specified delivery times may obtain less than the absolute dose that is required to fill the dose chamber.
Depending on the type of PCDD pump employed, a patient may also gain significantly greater doses of a medicament than he/she should receive, by using the device at frequent intervals before the dose chamber is completely full. For example, a patient who activates a mechanical PCDD pump once every few minutes for an hour will gain significantly greater amounts of a medicament than they should receive if they use the pump once every 10 minutes over a 1 hour period. This is because the most rapid filling in mechanically controlled PCDD lockout pumps occurs in the first minutes. In some circumstances a patient may, for example, receive more than 200% of the expected dose of medicament if he/she activates the device at shorter time intervals than recommended for medicament delivery. This phenomena has in the past led to patient overdose.
It has been found that by controlling the number of doses of a medicament that a patient receives per hour, it is possible to control many patient symptoms. In particular, patients can control their own symptoms by measuring the symptoms and adding doses of medicaments as required. In such situations physicians would choose the limit which will be an index of medicament safety for a certain dose to be delivered per hour.
DISCLOSURE OF INVENTION
The present invention seeks to provide an improved PCDD apparatus which is simple and inexpensive to manufacture and use, and which has a high level of inherent safety.
The present invention provides a delivery device for patient-controlled infusion of a medicament, the delivery device comprising: (i) a reservoir for the medicament; and (ii) a pump which has a predetermined delivery dose, wherein the pump comprises a first conduit which connects the reservoir to a pump chamber, a one-way valve in fluid communication with the first conduit and the pump chamber which permits medicament flow into the chamber but prevents reverse flow therefrom, a second conduit extending from the pump chamber and having a distal end through which the medicament may be released, and a controlling means in fluid communication with said pump chamber and said second conduit, wherein the first conduit is suitably adapted to restrict the flow of medicament into the chamber to a predetermined maximum delivery rate, and wherein the controlling means is adapted to: (a) open only when pressure within the dose chamber exceeds a pre-selected minimum opening pressure for the controlling means; and, (b) is adapted to prevent the reverse flow of medicament and air into the pumping means.
The present invention attempts to minimise the potential for patients to overdose with medicaments by providing a physical time delay between one dose and the next. This delay is created as a working interrelationship between the first conduit, the pumping means and the controlling means. The first conduit restricts the passage of medicament into the dose chamber thereby providing the dose chamber with a predetermined filling time. In combination the controlling means retards the release of medicament from the dose chamber until a suitable opening pressure (driving force) can be generated in the dose chamber to open the controlling means. Thus, an efficient lockout may be created whereby a patient is prevented from obtaining additional doses of a medicament from the delivery device until the chamber contains a suitable dose of spray to treat said patient's ailment.
The first conduit is preferably a fine calibre tube which has a very narrow bore and which limits the filling time of the dose chamber to between 1 minute and 12 hours. The desired time delay for filling the dose chamber would depend on a variety of factors such as the concentration of medicament to be delivered by the delivery device, the physical properties of the medicament, the delivery route, the delivery volume and the number of times that the medicament is to be delivered per day. Preferably, the time delay is between 1 and 60 minutes with 10 to 20 minutes being optimal. For example, the time delay may be 15 minutes.
Any fine calibre tubing that is able to limit the flow rate of medicament into the dose chamber to a desired fill time may be used in the invention. Such a tube and a method for producing it are described in co-owned international patent application WO88/02637. Preferably the tube is 1 to 700 cm in length is substantially resistant to kinking and has a lumen diameter of about 0.001 mm to 0.2 mm. For example, nasal spray apparatuses for the delivery of fentanyl which employ fine calibre tubing that have a lume
Frederickson & Byron, P.A.
Hayes Michael J.
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