Synthetic resins or natural rubbers -- part of the class 520 ser – Synthetic resins – Mixing of two or more solid polymers; mixing of solid...
Reexamination Certificate
1999-09-30
2001-06-19
Lipman, Bernard (Department: 1713)
Synthetic resins or natural rubbers -- part of the class 520 ser
Synthetic resins
Mixing of two or more solid polymers; mixing of solid...
C525S331800, C525S344000, C525S350000
Reexamination Certificate
active
06248841
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates to a process to reduce the residual peroxide levels in crosslinked ethylene-propylene diene monomer (EPDM) elastomer material and to inhalation devices containing EPDM gaskets made by the inventive process.
Metered-dose inhalers are commonly used to deliver medicaments to the respiratory system, particularly asthma and allergy medicaments. When a metered-dose inhaler is filled with medicament and shaken, the EPDM components are in direct contact with the medicament. The medicament is thus exposed to any residual peroxides in the gasket material. Applicants have found that these residual peroxides can cause significant oxidative degradation of the medicament. The longer the medicament is stored in the metered-dose inhaler in contact with the EPDM material, the more degradation occurs. Thus, the concentration of medicament significantly diminishes with storage time in the metered dose inhaler. This causes non-uniformity in patient dosing, because different dosages of medicament will be delivered with one inhaler actuation depending on how long the medicament has been stored in the inhaler.
Applicants have considered various approaches to reduce residual peroxides. For example, the peroxide may be reduced by use of different peroxide crosslink initiators during elastomer formulation or optimization of the elastomer curing process. The advantage of the present invention is that residual peroxides can be virtually eliminated with relative ease without the need to modify elastomer formulations or curing conditions. This avoids the need to retool the elastomer production process or to submit new information to regulatory agencies because of a change in formulation. Furthermore, Applicants' invention may be used in conjunction with other methods to further reduce residual peroxide levels.
SUMMARY
Applicants have identified a major cause of medicament degradation in medicaments stored in metered-dose inhalers and have invented a method to prevent or greatly reduce degradation. The EPDM valve components are exposed to a solution of a chemical reducing agent, such as an ethanolic solution of 2-mercaptoethanol. The reducing agent greatly diminishes the residual peroxide levels in EPDM by reducing the peroxide functional groups to the corresponding hydroxyl groups. EPDM components treated in this manner have demonstrated very low peroxide levels and, consequently, greatly improved compatibility with the pharmaceutical formulation in the inhaler. An advantage of this process is that the treated EPDM gasket material retains its favorable physical properties and its good performance in metering valves.
REFERENCES:
patent: Re. 32028 (1985-11-01), Fischer
patent: 3468855 (1969-09-01), Hunter
patent: 3607830 (1971-09-01), Kearnan et al.
patent: 3925333 (1975-12-01), Valvassori et al.
patent: 3957919 (1976-05-01), Von Bodungen et al.
patent: 5667858 (1997-09-01), Pokorny
D'Silva Joseph
Gelotte Karl M.
Aventis Pharmaceuticals Products Inc.
Lipman Bernard
Newman Irving
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