Surgery – Respiratory method or device – Means for mixing treating agent with respiratory gas
Patent
1994-10-12
1998-07-14
Asher, Kimberly L.
Surgery
Respiratory method or device
Means for mixing treating agent with respiratory gas
12820319, A61M 1500, A61M 1600, B05D 714, B65D 8306
Patent
active
057788731
DESCRIPTION:
BRIEF SUMMARY
This application is a 371 of PCT/GB93/00335 filed Feb. 18, 1993.
FIELD OF THE INVENTION
This invention relates to a metering device for transferring a desired volumetric dose of a flowable substance from a storage chamber containing the substance to a location outside the chamber, which device is of particular use in an inhaler for delivering a dose of a medicament or other substance for inhalation into the lungs of a user. The invention also relates, inter alia, to an inhaler incorporating such a metering device; to a method for transferring a desired volumetric dose of a substance from one location to another using such a device; and to a container for containing metered doses of a substance, the container incorporating one or more such devices.
BACKGROUND OF THE INVENTION
It is often necessary to transfer an accurate volume of a substance from a storage chamber containing that substance to another location, but it is not always easy to effect the transfer accurately and efficiently. In particular, it is often desired to transfer a powdered medicament from a storage chamber to an inhalation passage in a dry powder inhaler.
Powder inhalers, which deliver a drug in a dry, finely divided form, have been shown to give certain medical advantages over other forms of delivery system. In particular, they are more popular than inhalers which propel a drug in pressurised gas from an aerosol, because of environmental and other considerations.
EP-079478, EP-166294 and GB-2165159 disclose examples of dry powder inhalers which include a medicament storage chamber and an inhalation passage through which air is drawn via a mouthpiece. A metering member provided with a metering recess takes a dose of medicament from the storage chamber and deposits it in the inhalation passage.
It is considered that the accuracy of such arrangements can be very poor: on the one hand, by repeated indexing of the metering member it is possible to deposit two or more doses of medicament into the inhalation passage, resulting in the administration to the user of an overdose of medicament; on the other hand, since the medicament normally drops from the metering recess into the inhalation passage under gravity, particles of medicament can adhere to the interior of the metering recess so that an underdose is delivered.
US-2587215 discloses dry powder inhalers with the same disadvantages as those mentioned above. However, this document also discloses an embodiment in which the metering member presents the medicament in an upwardly open dispensing cup to a mixing chamber, where it is mixed with air before being sucked into an inhalation tube via a nozzle having a narrow opening. Air sucked into the inhaler passes into the inhalation tube either directly or through the mixing chamber and nozzle. Accordingly, not all the air passes over the dispensing cup. If medicament adheres to the surface of the dispensing cup but is not sucked therefrom, an underdose of medicament will be delivered to the user. Upon repeated use of a dispensing cup to deliver doses to the inhalation tube, a continually increasing amount of the medicament powder can adhere to the base of the dispensing cup, resulting in progressively decreased dosages to the user.
This build-up of adherent powder is thought to be a source of inaccurate dosing in many of the inhalers previously proposed.
Moreover, in the inhaler of US-2587215, the metering member is a rotary sliding device journalised on a cylindrical pivot member extending from the bottom of the body of the device. Such an arrangement is susceptible to jamming due to ingress of powdered medicament between the cylindrical contacting surfaces of the pivot member and the metering member.
Another form of inhaler which is currently available includes a metering member having a number of tapered metering recesses which are open at top and bottom. In use, finely divided medicament from a storage chamber is packed into the recesses, whereupon the metering member is moved to a dispensing position in which air can be drawn through
REFERENCES:
patent: 1858735 (1932-05-01), Goodsell
patent: 2587215 (1952-02-01), Priestly
patent: 4604847 (1986-08-01), Moulding, Jr. et al.
patent: 4635829 (1987-01-01), Brittingham
patent: 4934358 (1990-06-01), Nilsson et al.
patent: 5447151 (1995-09-01), Bruna et al.
Asher Kimberly L.
Innovata Biomed Limited
Schindler Edwin D.
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