Surgery – Liquid medicament atomizer or sprayer – Pre-pressurized container holding medicament
Reexamination Certificate
2001-05-11
2003-09-30
Lo, Weilun (Department: 3761)
Surgery
Liquid medicament atomizer or sprayer
Pre-pressurized container holding medicament
C128S200140, C128S200190, C128S203120, C222S635000
Reexamination Certificate
active
06626171
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
This invention relates to a metering valve and more particularly, to a metering valve utilizing a metered amount of a fluid or compressed gas carrier combined in a mixing chamber with a metered amount of a medicament and the like. The ingredients are measured and transported by a dosing means under conditions whereby a gaseous medicament dispersion is formed.
2. Description of the Prior Art
Metered dose inhalers (MDIs first introduced in 1956) are self-contained packages usually consisting of an aluminum can and a lid with a metering valve crimped on it. The formulation inside the can usually consists of propellant(s) and drugs, either in solution or suspension, along with excipients to aid in stability and dosimetry of the product. The valve system is fitted to an actuator along with a mouthpiece, which links the canister to the patients' mouth. When the valve is actuated a pre-metered volume of the formulation is released through the valve into the mouthpiece. The latent heat of vaporization of the volatile propellant provides the energy for atomization of droplets of product released from the valve. Usually, a partial evaporation of about 10-20% of propellant vehicle occurs immediately after expulsion of product from the nozzle. It is this violent evaporation of propellant that causes instant break-up of aerosol droplets into fine respirable particles, usually ≦10 &mgr;m subsequently yielding particles with a mass median aerodynamic diameter (MMAD) in the range between 3 and 8 &mgr;m.
Chloroflurocarbons (CFCs) are substituted halogenated alkanes used extensively in the pharmaceutical industry because they are inert, non-toxic and possess enough vapor pressure to warrant their use as drug delivery carriers in pharmaceutical aerosols. Aerosolized beta-agonists and anti-allergic compounds were the first series of pharmaceuticals to use CFCs as propellants for drug delivery to the lung. For these products, appropriate combinations of CFC propellant blends are necessary to insure a proper balance between vapor pressure and device performance. Such propellant combinations enable the formation of a fine spray upon actuation of the delivery mechanism. The use of a metering valve allows delivery of a predetermined volume of the product upon actuation. Hence, these delivery systems are also referred to as metered-dose inhalers (MDIs). These CFC propellants are suggested to interfere with stratospheric ozone protection. In 1991, the total consumption of CFCs in medical aerosols was estimated to be about 0.5% of the total worldwide consumption of these materials, but despite such low levels of CFCs consumed in MDIs, environmentally conscious groups are committed to see a total ban on the production and use of these products. There are medical, ethical and social consequences for abandoning CFCs totally before suitable alternatives are available.
The need to replace CFCs in clinical and industrial applications based on scientific, medical and environmental mandates, including the Montreal Protocol, has led to large research programs to identify and test acceptable substitutes. A number of possible alternative propellants have been rejected for safety reasons. Some, for example compressed gases, simply do not have the physical properties needed to achieve uniform doses from MDIs. Others, for example hydrocarbons, are unsuitable because of their flammability. Yet others are toxic because they cause drowsiness or affect the heart. Attention is now being focussed on two hydrofluoroalkanes (HFAs), HFA-134a and HFA-227, respectively called tetrafluorethane and heptafluoropropane. These propellants appear to have the necessary physical properties, do not cause ozone depletion, are non-flammable and, most importantly, appear to be non-toxic when compared to CFCs at equivalent doses. Establishing the suitability of these alternative propellants before introducing them for use in MDIs involves a lengthy and highly regulated process. The significant progress made thus far is a reflection of the substantial development effort made by the pharmaceutical industry to phase out CFCs from MDIs while maintaining the range of treatment options available for patients.
Although HFAs possess several desirable properties which make them suitable, effective and safe alternatives to CFC propellants, they nonetheless are greenhouse gases and have the potential to cause undue global warming (e.g., warming of oceans, and water evaporation, which would further delay the transmission of heat). Thus, future drug delivery systems should concentrate on technology platforms that are truly inert to the environment.
More recently, electronically-controlled devices which use aqueous formulations in a manner similar to conventional MDIs have been developed. Piezo devices produce a spray out of a single drop of drug solution. The drug is metered by a nozzle onto a mesh or grid. The device usually consists of an actuator head, a housing, a piezo-electric element, and a mesh. The liquid droplet on the mesh is energized by the piezo-electric element using an alternating voltage thus causing vibrations of drug molecules in the droplet. The vibrations are amplified by the housing. This causes the mesh and the liquid droplet to also vibrate subsequently resulting in spray formation. Particle size thus depends on the flow rate of drug solution onto the mesh. Particle size distribution of the aerosolized particles depend also on the hole size in mesh, number of holes in the mesh, and magnitude of the vibrational energy.
Nebulized inhalation systems are aqueous formations which are aerosolized with the aid of external energy. The process converts water droplets to the vapor phase, which is inhaled by the patient. Unlike MDIs, the composition of these systems resembles injectable formulations and is administered with specific devices, namely compressors and atomizers. The formulations generally contain dissolved drug but suspensions of the drug together with other inactive excipients may be neubulized for stability and taste reasons. At the time of use, the solution is poured into the nebulizer, which generally contains an ultrasonic probe or an air jet source to aid aerosolization. A mouthpiece or hood traps the resulting particles so that tidal breathing may be used by the patient to inhale the drug. Nebulizers are not compact like MDIs and they are often too bulky for ambulatory use. In addition, they take several minutes to hours to complete the dosing. In spite of this limitation, nebulizers offer several significant advantages. They contain mainly water as a vehicle and therefore present no great safety concerns in regard to formulation toxicity.
Nebulizers present a variety of dosing schemes and dose volumes so that they are flexibly adaptable for drugs whose activity is so low as to require several milligram to gram quantities to obtain measurable pharmacologic effects. However, there are a number of technical and clinical limitations concerning nebulized drug technologies. Sterility of drug formulations, the need for ancillary hardware, example generator, and their suitability to non-ambulatory care because of size, places them at a disadvantage.
Unlike MDIs and nebulizers, where drug solution or suspension is initially released as a “wet” spray, DPIs constitute formulations and devices where a predetermined dose of active, either alone or in a blend with some carrier like lactose, is released as a fine mist of dry powder for inhalation. These systems differ significantly from MDIs and nebulizers in that they do not contain any liquid media (e.g., propellant or water). The drug is formulated in a manner so that it readily disperses into particles of respirable size range (i.e. ≦10 &mgr;m). The powder dispersion is initiated either by inspiration or by some external source, e.g., an electronic vibrator included with the device hardware. In older DPI technologies, the formulation to be inhaled was packaged in single dose units, for example in hard gelatin capsule
Adjei Akwete L.
Genova Perry A.
Sexton Frederick
Frommer & Lawrence & Haug LLP
IEP Pharmaceutical Devices Inc.
Lo Weilun
Mendoza Michael
Santucci Ronald R.
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