Surgery – Respiratory method or device – Means for mixing treating agent with respiratory gas
Reexamination Certificate
1998-05-28
2001-02-06
Weiss, John G. (Department: 3761)
Surgery
Respiratory method or device
Means for mixing treating agent with respiratory gas
C128S203120
Reexamination Certificate
active
06182655
ABSTRACT:
AREA OF APPLICATION OF THE INVENTION
The invention relates to a dry powder inhaler with dosed administration of a medical preparation upon inhalation by the patient. The dry powder—in loose form or pre-dosed units for dispensing—is contained in a medicament reservoir. The invention concerns the generic type of inhalers in which, upon activation, a defined dose is first of all introduced from the internal medicament reservoir into the inhalation channel by means of a portioning mechanism, and from there the patient draws this defined dose into his airways via a mouthpiece, in a flow of air generated by aspiration.
Inhalation is a proven method of depositing medicinal agents in the lungs or delivering them to the blood. Thus, in addition to the devices for atomizing or nebulizing of liquids, for example by means of air, compressors, ultrasound, liquefied propellant gases (fluorohydrocarbons, fluorochlorinated hydrocarbons), inhalers for pulverulent preparation with dosed portioning were also developed for the purpose of inhalation.
A defining feature of inhalers is that the active substance particles of the medicament are deposited, by inhalation, in a defined dose and particle size (about 1-6 &mgr;m) either in the central or peripheral lung compartments (topical treatment) or as very small particles by means of absorption in the alveolar region into the blood stream of the patient (systemic treatment).
However, micronized particles with the diameter in question here have extremely poor flow characteristics. This problem is solved by a number of conventional methods. Thus, powder mixtures are produced with a carrier which generally has a greater particle diameter than the active substance, with the active substance particles depositing themselves on the carrier surface. On the other hand, in the manufacture of soft pellets, a large number of active substance particles are massed together to form respectively larger particles, the pellets. Under the effect of force, the pellets split up again into the individual, smaller active substance particles. During inhalation it should be possible with the inhaler to detach the active substance particles from the carrier or to break the pellets up again into small particles. Simple swallowing of the medicament is completely undesirable. For this reason, special functional demands are imposed on inhalers in principle.
PRIOR ART
EP-A-0 404 454 and EP-A-0 558 879 disclose inhalers for single use. Such designs are appropriate only for special applications, since on the one hand the patient has no control over the correct use, i.e. the optimum inhalation, and on the other hand a new inhaler has to be used for each inhalation, which is costly, inconvenient and not environmentally friendly.
Thus, inhalers with a dry powder as medicament were developed also for multiple use. WO 93/03782 discloses an inhaler with a medicament reservoir and a dosing mechanism, by means of which the medicament is conveyed in doses from the storage container into the inhalation channel and can be sucked from there with the flow of air generated by the patient. This inhaler does not yet satisfy all the requirements. The exact and prescribed use can still not necessarily be sufficiently guaranteed. The dosing accuracy has to be increased; humidity too easily penetrates into the inhaler, the deagglomeration and atomization have to be improved, and keeping the inhaler clean is complicated.
U.S. Pat. No. 5,239,992 discloses a further inhaler in which a dosing cavity is present in a longitudinally displaceable piston rod and this dosing cavity, first positioned under the medicament reservoir, receives a dose of medicament. The patient has to inhale counter to the force of a spring, so that the piston rod moves and the ready-to-use dose can be sucked by the patient through suction openings in the guide channel of the piston rod. In principle, this inhaler too exhibits the abovementioned inadequacies.
WO 94/05359 describes an inhaler for multiple dosed administration of a pharmacological dry powder which is contained within a medicament reservoir provided inside the housing. On the inhaler a mouthpiece is joined which is closed outside inhalations by a folding down protective cap. The inhaler further has inside a horizontally movable carriage with a dosing depression. If the protective cap is closed the dosing depression is positioned underneath the funnel-shaped outlet of the medicament reservoir, so that dry powder by its gravity should flow into the dosing depression until it is full if the inhaler is in a vertical position. One filling of the depression represents one dose.
After a preceding inhalation a spring arranged above a bellows is tensed by closing the protective cap. The bellows is placed on the medicament reservoir, an air permeable membrane is provided as a separating wall. During opening the protective cap, the locking of the tensed spring is released, so an air pressure pulse acts upon the medicament reservoir. This air pressure pulse ought to guarantee that in each case the dosing depression is properly filled with dry powder. The carriage is moved by further opening of the protective cap, so the dosing depression is positioned within a suction channel. With the inhalation the medicament dose is sucked out from the dosing depression through the mouthpiece. The mouthpiece has at one side a flange for joining to the housing of the inhaler and has at the other side a suction pipe outwardly trumped-like opening. A flow channel flows tangentially into the flange which channel is connected with the suction channel, where the medicament dose is available in readiness for inhalation. At the flange, tangentially arranged air openings are provided for the purpose of turbulence of the medicament containing air stream sucked into the mouthpiece.
The spring above the bellows again tenses by closing the protection cap and the carriage goes back into its starting position, so the dosing depression is again positioned underneath the funnel-like outlet of the medicament reservoir and the next inhalation cycle can start.
The previously described inhaler and its pertinent mouthpiece shows the following essential disadvantages:
Independent of the intensity of the inhalation, the medicament from the dosing depression can be sucked out too low such that the medicament particles only insufficiently arrive at their intended position within the patient's respiratory ducts and/or actually only a part of the dose available is sucked out. Thus the patient has no control as to whether the inhalation has been actually done or correctly completed.
After opening the protective cap and during inhalation, the inhaler has to be positioned vertically, otherwise the dry powder can flow back from the dosing depression into the medicament reservoir or come into the suction channel situated above the dosing depression and deposit there as a loss. A construction feature is missing which obligates or requires the patient to apply the inhaler in the right functional position, i.e., not in an angled or oblique position in which the medicament does not flow or flows insufficiently into the channel inside the inhaler from which the patient inhales the powder.
At lease a part of the dry powder of the unused dose can come into the suction channel if the inhalation is incompletely finished or not done at all and the inhaler is not held strictly vertically. By the next inhalation cycle it is metered again, and therefore inaccuracies of the dosage can emerge. Based on the construction, double dosages or dosages under the limit can happen.
The extending bellows sucks in a larger amount of external air with each closing of the protective cap, thereby permitting moisture to enter the medicament reservoir. This is disadvantageous for the flowability and the accuracy of metering of the dry powder as known from the literature and the practice.
A further construction feature is missing which guarantees that the last 5 to 10 nominal doses in the declared measure (weight and volume) can be delivered in order to
Eggimann Thomas
Keller Manfred
Jago Research AG
Selitto & Associates
Weiss John G.
Weiss, Jr. Joseph F.
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