Drug – bio-affecting and body treating compositions – Designated organic active ingredient containing – Radical -xh acid – or anhydride – acid halide or salt thereof...
Reexamination Certificate
1999-04-06
2002-08-06
Krass, Frederick (Department: 1614)
Drug, bio-affecting and body treating compositions
Designated organic active ingredient containing
Radical -xh acid, or anhydride, acid halide or salt thereof...
C514S617000, C514S619000, C514S620000, C514S626000, C514S817000, C514S944000, C514S947000
Reexamination Certificate
active
06429228
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a local anesthetic for external use. In particular, the present invention relates to a local anesthetic for external use, which is conveniently usable and applicable to a broad skin surface, and which is excellent in percutaneous absorption and quick efficacy as well as excellent in stability.
BACKGROUND ART
The percutaneous absorption type local anesthetic for external use has advantages in that, for example, it does not require any special technique upon administration, it does not cause any pain, and it makes it possible to anesthetize a broad skin surface, as compared with other types of anesthetics administrated by injections such as cuteneous or subcuteneous injections. Accordingly, the percutaneous absorption type local anesthetic for external use has been considerably investigated (Japanese Laid-Open Patent Publication Nos. 57-81408, 4-305523, and 6-40947). In medical facilities such as hospitals, the local anesthetic for external use is sometimes used in accordance with a method in which an active anesthetic ingredient is blended with, for example, an agent of ointment, cream, or gel to prepare a nosocomial or clinically formulated local anesthetic which is tightly sealed, upon administration, with an extremely air-tight resin film such as a polyvinylidene chloride film (“ODT method”; Hifu, 34 (2), 237-242 (1992)). Recently, a tape-shaped medicament has been developed, and it has been commercially available for medical use.
However, the following problems have been pointed out for the conventional pharmaceutical preparations. Namely, any of the pharmaceutical preparations described in the respective patent documents is insufficient in percutaneous absorption and quick efficacy. As for the nosocomial local anesthetic pharmaceutical preparations formulated, for example, as the ointment, the cream, or the gel form agent, some of the pharmaceutical preparations have poor stability, and hence it is necessary for such pharmaceutical preparations to be prepared when they are used. Further, other of the pharmaceutical preparations are inconvenient for use, and they require a long time to express the anesthetic effect. Moreover, the tape-shaped medicament is unsuitable to anesthetize a broad skin surface. Although the anesthetic is blended at a high concentration (30 to 60%), the tape-shaped medicament is deficient in percutaneous absorption and quick efficacy.
DISCLOSURE OF THE INVENTION
The present invention has been made taking the foregoing viewpoints into consideration, an object of which is to provide a percutaneous absorption type local anesthetic for external use which is conveniently used when it is applied and peeled off, which is applicable to a broad skin surface, and which is excellent in percutaneous absorption and quick efficacy as well as excellent in stability.
As a result of diligent investigations performed by the present inventors in order to achieve the object described above, it has been found that when an active ingredient selected from lidocaine, prilocaine, and pharmaceutically acceptable salts thereof is allowed to be contained in a mixed solution comprising water and lower alcohol such as ethanol and isopropyl alcohol, and a resultant solution is allowed to further contain a percutaneous absorption accelerator to formulate a pharmaceutical preparation so that it is used as a percutaneous absorption type local anesthetic, then it is possible to improve the percutaneous absorption of the active ingredient and shorten the time required to express the anesthetic effect, and the pharmaceutical preparation containing the foregoing components is excellent in stability. Thus the present invention has been completed.
Namely, the present invention lies in a local anesthetic for external use, containing a) an active ingredient selected from lidocaine, prilocaine, and pharmaceutically acceptable salts thereof, b) a percutaneous absorption accelerator, c) ethanol and/or isopropyl alcohol, and d) water.
Specifically, the b) percutaneous absorption accelerator contained in the local anesthetic for external use of the present invention preferably includes fatty acids each having a number of carbon atoms of 8 to 18 and pharmaceutically acceptable salts thereof. Among these compounds, those more preferably used include caprylic acid having a number of carbon atoms of 8, oleic acid having a number of carbon atoms of 18, and pharmaceutically acceptable salts thereof.
Specifically, the local anesthetic for external use of the present invention contains c) ethanol and/or isopropyl alcohol and d) water preferably in a ratio of content within a range of 0.5 to 1.2 as expressed by a weight ratio of ethanol and/or isopropyl alcohol to water. The local anesthetic for external use of the present invention preferably has a pH within a range of 6.0 to 8.5.
As for the form of agent, for example, the local anesthetic for external use of the present invention is preferably applied as a gel form agent.
The present invention will be explained in detail below.
The local anesthetic for external use of the present invention contains a) the active ingredient selected from lidocaine, prilocaine, and pharmaceutically acceptable-salts thereof, b) the percutaneous absorption accelerator, c) ethanol and/or isopropyl alcohol, and d) water. The foregoing respective components a) to d) will be successively explained below.
a) Lidocaine, Prilocaine, and Pharmaceutically Acceptable Salts Thereof
Both of lidocaine and prilocaine are compounds known as local anesthetics. These compounds are easily obtained by chemical synthesis. Therefore, chemically synthesized products known as described above can be used for the local anesthetic for external use of the present invention. In general, these compounds are commercially available. Therefore, it is also possible to use commercially available products in the present invention. The local anesthetic for external use of the present invention contains, as the active ingredient, lidocaine or prilocaine singly, or a mixture of them. However, the local anesthetic for external use of the present invention can contain one or more pharmaceutically acceptable salts of lidocaine and prilocaine in place of them or in addition to them. The pharmaceutically acceptable salts specifically include, for example, hydrochloride of lidocaine and hydrochloride of prilocaine.
In the local anesthetic for external use of the present invention, the content of the active ingredient selected from lidocaine, prilocaine, and pharmaceutically acceptable salts thereof is preferably about 2 to 12% by weight, and more preferably 5 to 10% by weight with respect to the total amount of the pharmaceutical preparation, however, the content of the active ingredient varies depending on the type or form of agent, the position at which the agent is used, and the method with which the agent is used.
b) Percutaneous Absorption Accelerator
The percutaneous absorption accelerator contained in the local anesthetic for external use of the present invention is not specifically limited provided that the absorption accelerator has a function to accelerate percutaneous absorption of lidocaine, prilocaine, and pharmaceutically acceptable salts thereof as the active ingredient of the local anesthetic for external use of the present invention, and that the absorption accelerator is a pharmaceutically acceptable compound. Specifically, those preferably used as the percutaneous absorption accelerator include fatty acids each having a number of carbon atoms of 8 to 18 and pharmaceutically acceptable salts thereof. The fatty acid having a number of carbon atoms of 8 to 18 includes, for example, caprylic acid, capric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, and linolenic acid. Among these compounds, those more preferably used for the local anesthetic for external use of the present invention are exemplified by caprylic acid having a number of carbon atoms of 8, and oleic acid having a number of carbon atoms of 18. The pharmaceutic
Inagi Toshio
Mada Akira
Kilpatrick & Stockton LLP
Kowa Company Ltd.
Krass Frederick
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