Drug – bio-affecting and body treating compositions – Preparations characterized by special physical form – Implant or insert
Patent
1995-06-30
1997-04-15
Azpuru, Carlos A.
Drug, bio-affecting and body treating compositions
Preparations characterized by special physical form
Implant or insert
5147723, A61F 202, A61K 4730
Patent
active
056206976
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for preparing pharmaceutical compositions using ultrasonic processing.
Matrix-type drug delivery systems, which are capable of releasing pharmaceuticals in a controlled fashion over extended periods of time are well known. Drug releasing matrices have previously been prepared by conventional polymer processing techniques, such as injection molding, extrusion or compression molding. These techniques often lead to noticeable decomposition of the active agent and/or the polymer, or are slow and cumbersome to use. The factors mainly responsible for their degradative effects are long heating times combined with mechanical stress caused by screws or other mixing devices in the machinery. The problems created by heat can be avoided by solvent casting, but this method may result in harmful solvent residues, and it is not suitable for insoluble polymers, such as polyglycolic acid (PGA).
It is an object of the present invention to provide a method for preparing drug releasing compositions eliminating the disadvantages discussed above. The object is realized by a method for preparing a drug releasing biodegradable composition comprising biodegradable polymer matrix and at least one pharmaceutical substance mixed and/or dissolved within said matrix, characterized in that using ultrasonic means a mixture of the biodegradable polymer and the pharmaceutical substance is at least partially melted.
Ultrasonic techniques are widely used in industry for the joining of thermoplastic moldings, e.g. in car and textile industry. It has now been found that ultrasonic processing can successfully be used to plasticize and mold polymeric drug delivery systems. Compared to the previously utilized methods, ultrasonic molding offers the advantage of being faster, more controllable, and substantially less destructive to the polymer and the drug.
Ultrasonic molding is based on a process in which energy from the main supply is converted by a generator into electrical vibrations in the US range (usually 20 kHz), and further transduced into mechanical vibrations of the same frequency. These mechanical vibrations are transmitted to the work pieces through a booster (transformer) and a sonotrode. The heating in the materials to be molded or joined takes place as a result of the absorption and reflection of the mechanical vibrations in the material and the interface friction of the fragments or joining surfaces.
The time required for ultrasonic processing is always very short, preferably less than 1.5 s. This fact is influential in all applications, particularly when mass-produced articles are in question. Short heating times are especially important in drug release applications, in which neither the polymer nor the active agent can withstand elevated temperatures for long periods of time.
Ultrasonic molding of polymer/drug composites is accomplished by standard ultrasonic welding equipment, provided it is supplied with a sonotrode and a mold suitable for producing of matrices of desired size and geometry. Tablet- or rod-shaped matrices, for example, are easily produced, but more complicated geometries can also be prepared.
Polymeric materials suitable for ultrasonically processed drug releasing matrices include e.g. polyorthoesters and biodegradable poly-.alpha.-hydroxy acids, such as polyglycolide (PGA), polylactides (PLA), polyhydroxybutyrate (PHB) and PHB/polyhydroxyvalerate (PHV) copolymers. Many of these materials are extremely difficult to injection mold or extrude due to their narrow melting temperature ranges. The process may, in fact, become impossible to control when the polymers have been blended with pharmaceuticals: drastic changes in the viscosity of the materials can occur within a 0.5.degree. C. change in temperature or with time, and differences in the melting points of the constituents often result in one or more of the substances being at least partially destroyed. In ultrasonic molding these problems can largely be avoided, because the process is almost instantaneous, and because t
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Miettinen-Lahde Saila S.
Tormala Pertti O.
Azpuru Carlos A.
Leiras Oy
Orion-yhtyma Oy
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