Methods, uses and compositions of fluid petrolatum

Details Methods, uses and compositions of fluid petrolatum Methods, uses and compositions of fluid petrolatum

1999-09-15

2001-10-30

Kishore, Gollamudi S. (Department: 1615)

Drug, bio-affecting and body treating compositions

Preparations characterized by special physical form

Liposomes

C424S401000, C424S043000, C424S600000, C424S617000, C428S402200, C514S847000

Reexamination Certificate

active

06309664

ABSTRACT:

BACKGROUND
Petrolatum and its manufacture were initially patented in 1872 by Robert A. Cheeseborough (U.S. Pat. Ser. No. 127,568). Although Cheeseborough cited treating leather as its primary use, petrolatum was also recommended as a hair pommenade and for treating chapped hands. In 1875, the American Pharmaceutical Association found petrolatum “without a superior” for treating burns and scalds. Since then, petrolatum's beneficial properties for skin care and treatment have been extensively studied and reported.
Petrolatum has been found to be the best material for relieving ordinary xerosis (Morrison et al.,
Cos & Toil
. (1996) 111:59). Petrolatum's moisturizing characteristics have been ascribed to the slowed water loss when petrolatum is applied to the skin. Petrolatum has also been used extensively on wound dressings, both as a treatment and as a pharmaceutically acceptable ointment base to deliver other medicinal compositions.
However, the same hydrophobic properties which make petrolatum an effective moisture barrier, also make it difficult to evenly disperse in fluid aqueous preparations. When mixed with water, petrolatum immediately forms a separate distinct layer. Evenly dispersed fluid preparations are essential for commercial manufacturing techniques, such as spraying. This is true for petrolatum encapsulated in lipid vesicles as well as unencapsulated products.
Accordingly, it is an object of the present invention to provide methods and compositions relating to a sprayable petrolatum product consisting of lipid vesicles encapsulating petrolatum, dispersed in an aqueous phase.
Another object of this invention is to provide a stable dispersion of petrolatum containing lipid vesicles in water.
These and other objects and features of the invention will be apparent from the following descriptions.
SUMMARY OF THE INVENTION
The invention features a sprayable petrolatum product having lipid vesicles encapsulating petrolatum dispersed in an external aqueous phase. The vesicles comprise a primary wall forming material and a weighting agent. The primary wall forming material is selected from the group consisting of nonionic and zwiterionic surfactants and the weighting agent is present in an amount sufficient that the lipid vesicles have a density of about 0.95-1.0 g/ml. Examples of preferred weighting agents include, for example, high molecular weight polyoxyethylene sorbitan esters, ester gum, metal oxides (e.g., iron oxide), and combinations thereof. Advantageously, the primary wall forming material has the property that it will form a lipid vesicle in the absence of said weighting agent. Preferably, petrolatum comprises at least about 20%, and more preferably about 30%, by weight of the lipid vesicles.
The invention also pertains to a method for protecting the skin of a mammal by contacting the skin with a sprayable pharmaceutical petrolatum composition product. The sprayable pharmaceutical petrolatum composition product includes lipid vesicles encapsulating petrolatum dispersed in an external aqueous phase. These lipid vesicles comprise a primary wall forming material and a weighting agent. The primary wall forming material is a nonionic or a zwiterionic surfactant, and the weighting agent is present in an amount sufficient that the lipid vesicles have a density of about 0.95-1.0 g/ml. The preferred primary wall forming materials are polyoxyethylene glyceryl fatty acids, C
12
-C
18
fatty alcohols, C
12
-C
18
glycol monoesters, C
12
-C
18
glyceryl mono- and diesters, polyoxyethylene fatty alcohols, betaines, sarcosinates, propylene glycerol stearate, sucrose distearate, glycerol dilaurate, glucosides, and mixtures thereof.
DETAILED DESCRIPTION OF THE INVENTION
The invention pertains to, at least in part, a sprayable petrolatum product having lipid vesicles encapsulating petrolatum dispersed in an external aqueous phase. The vesicles comprise a primary wall forming material and a weighting agent. The primary wall forming material is selected from the group consisting of nonionic and zwiterionic surfactants and the weighting agent is present in an amount sufficient that the lipid vesicles have a density of about 0.95-1.0 g/ml. Preferably, petrolatum comprises at least about 20%, e.g., more preferably 30%, by weight of the lipid vesicles. In a further embodiment, the lipid vesicles are paucilamellar.
Petrolatum has been commercially available since the mid-1870's. Commonly, it is a semisolid mixture of hydrocarbons and is, essentially, both odorless and tasteless to humans. Petrolatum is often obtained through the dewaxing of heavy mineral oils.
The primary wall forming material, which constitutes the greatest structural material by weight of the bilayers (e.g., 10-20%), can be any suitable non-ionic surfactant known in the art to be useful in forming vesicles. For example, suitable surfactants are disclosed in U.S. Pat. No. 5,260,065, entitled “Blended Lipid Vesicles;” U.S. Pat. No. 5,234,767, entitled “Lipid Hybrid Vesicles;” U.S. Pat. No. 5,439,967 entitled “Propylene Glycol Stearate Vesicles;” U.S. Pat. No. 5,405,615, entitled “Sucrose Distearate Vesicles,” and U.S. Pat. No. 5,160,669, entitled “Method of Making Oil Filled Paucilamellar Lipid Vesicles,” the contents all of which are incorporated by reference herein. Advantageously, the primary wall forming material has the property that it will form a lipid vesicle in the absence of said weighting agent. In another embodiment, the primary wall forming material of the vesicle bilayers is selected from the group consisting of polyoxyethylene glyceryl fatty acid esters (e.g., having 1-10 polyoxyethylene groups), such as polyoxyethylene glyceryl monostearate and polyoxyethylene glyceryl monooleate, C
12
-C
18
fatty alcohols, C
12
-C
18
glycol monoesters, C
12
-C
18
glyceryl mono-and diesters, and mixtures thereof. Preferred primary wall forming material are selected from the group consisting of C
16
and C
18
fatty alcohols, glyceryl mono- and distearate, glyceryl dilaurate, glycol stearate, and mixtures thereof. All of the aforementioned compounds are commercially available. Preferred primary wall forming materials include C
16
-C
18
fatty alcohols, glycol stearate, glyceryl mono- and distearate, glyceryl dilaurate, and combinations thereof.
The term “weighting agent” includes substances which affect the specific gravity of the lipid vesicles. Advantageously, the weighting agents increase the specific gravity of the vesicles to aid dispersion of the vesicles through out an aqueous mixture and to deter separation between the aqueous and lipid components of the mixture. Preferably, the inclusion of the weighting agents increases the specific gravity of the vesicles into the desired stable product range, e.g. greater than 0.95 g/mL to about 0.99 g/mL. In some embodiments of the invention, the weighting agents are incorporated directly into the walls of the vesicles. Preferred weighting agents include compounds with a specific gravity greater than 1.0 g/mL, (e.g., greater than 1.0 g/mL to about 2.0 g/mL). Examples include high molecular weight polyoxyethylene sorbitan esters, ester gums, metal oxides (e.g., iron oxide), and combinations thereof.
The lipid vesicles of the invention may further include one or more charge producing agents which minimize flow of the external aqueous phase into the vesicles. Preferred charge producing agents include negatively charged hydrophilic molecules such as sodium lauryl sulfate, sodium laureth sulfate, sodium lactate, sodium pyrrolidone carboxylate, aloe vera, retinoic acid and urea. Other possible negative charge producing agents include oleic acid, dicetyl phosphate, palmitic acid, cetyl sulphate, retinoic acid, phosphatidic acid, phosphatidyl serine, and mixtures thereof. Alternatively, also contemplated is the incorporation of positively charged molecules in order to provide a net positive charge to the vesicles. Examples of suitable positively charged molecules include, for example, long chain amines, e.g., stearyl amines or oleyl amines, long chain pyridinium c

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