Link:  Pharm/Biotech Resources

Title:  Effervescent solid composition of matter

United States Patent:  6,896,902

Issued:  May 24, 2005

Inventors:  Mathisen; Torbjörn (Älvsjö, SE); Back; Marcus (Vällingby, SE); Hellman; Åsa (Upplands Väsby, SE)

Assignee:  MEDICARB AB (Bromma, SE)

Appl. No.:  120607

Filed:  April 12, 2002

An effervescent solid composition of matter is provided, which comprises, as an active component, a substance selected from chitosan, its derivatives and salts thereof and a second component capable of releasing CO₂ in an acidic environment. Also, methods for treatment of a mammal suffering from a dermal wound, or for prophylactic or wound-healing treatment of lactating animals prone to develop or suffering from mastitis, are provided. The methods comprise the steps of:

FIELD OF INVENTION

The present invention relates to solid compositions of matter comprising an anti-microbial substance based on chitosan, its derivatives or salts thereof. The invention also involves a method for prophylactic or wound-healing treatment of lactating animals.

BACKGROUND OF THE INVENTION

The main active principle in the solid composition of matter involved in the present invention is selected from chitosan, its derivatives or salts thereof. Chitosan is a well-known polysaccharide which is composed of β(1-4)-linked N-acetyl-D-glucosamine and D-glucosamine units. Chitosan is manufactured by alkaline treatment of chitin, a polymer forming the shell of inter alia insects and crustaceans. Commercially, chitosan is recovered from crab- and shrimpshells that are waste products from the fishing industry. When treating chitin with alkali, usually sodium hydroxide, N-deacetylation takes place, i e acetamido groups are converted to amino groups, as the chitin is transformed to chitosan. By controlling the alkaline treatment of chitin it is possible to manufacture chitosans with varying degrees of N-acetylation.

Physical properties of chitosan, its derivatives and salts thereof, which properties affect its utility, depend on the degree of N-acetylation, the {overscore (Mw)}, the molecular weight distribution and the distribution of N-acetyl groups. Furthermore, different acid addition salts and derivatives of chitosan exhibit different properties.

It is also known that chitosan, its derivatives and salts thereof are biologically active and inter alia show anti-microbial properties.

Chitosan and derivatives and salts thereof are used in many forms, such as in solutions for the control of microbial growth. Examples of such solutions are solutions used as teat-dipping agents to prevent onset of mastitis in lactating cattle, as in e g WO 98/48627, as well as solutions for other anti-microbial uses.

One problem encountered in the use of solutions of chitosan, or of derivatives or salts thereof, is lack of stability of such solutions, especially when stored at elevated temperatures.

The dissolution of chitosan, or of derivatives or salts thereof, or indeed of any polysaccharide, is often problematic when performed without vigorous stirring. Instead of dissolving, the polysaccharide material will form lumps with a gel-like shell efficiently prohibiting further dissolution of the material.

Furthermore, transportation of dilute solutions of chitosan, or of derivatives or salts thereof, is expensive and involves handling problems in preparation and use. Also, storage facilities for dilute solutions can be costly and therefore disadvantageous.

Another possibility to solve storage and transportation problems would be to prepare concentrated solutions. However, this is not possible since chitosan forms very viscous solutions already at a low concentration, preventing the preparation of highly concentrated solutions. Another problem with chitosan solutions, and especially concentrated solutions, is that the viscosity decreases over time, due to hydrolytic degradation.

SUMMARY OF THE INVENTION

The present invention has for a main object to provide effervescent solid compositions of matter comprising, as an active principle, a substance selected from chitosan, its derivatives and salts thereof.

Another object of the invention is to provide such a composition of matter, thereby avoiding transportation and storage of aqueous solutions or suspensions of the active principle, since such solutions or suspensions can be easily prepared by the consumer at the time of use.

Yet another object of the invention is to provide such compositions of matter, which are stable in storage for a prolonged time before use thereof.

A further object of the invention is to provide solid compositions of matter comprising a substance selected from chitosan, its derivatives and salts thereof, which substances are otherwise not readily dissolved or suspended, which compositions are readily dissolved or suspended in aqueous liquid.

Still another object of the invention is to provide effervescent solid compositions of matter comprising, in addition to a substance selected from chitosan, its derivatives and salts thereof, a substance selected from heparin, heparan sulfate, dextran sulfate and other negatively charged polysaccharides or polymers.

A further object of the invention is to provide solid compositions of matter, such that solutions or suspensions made thereof, when used as teat-dipping agents, upon drying will form films on the areas treated.

Another object of the present invention is the provision of methods for wound-healing treatment of mammals.

Still another object of the invention is to provide a method for prophylactic or wound-healing treatment of lactating animals prone to develop or suffering from mastitis, particularly cows.

For these and other objects which will be evident from the following disclosure, the present invention provides an effervescent solid composition of matter comprising as an active component a substance selected from chitosan, its derivatives and salts thereof and a second component capable of releasing CO₂ in an acidic environment.

The composition of matter according to the invention preferably contains less chitosan, or derivative or salt thereof, than 50% by weight of chitosan, more preferably less than 25% by weight of chitosan. In keeping with the objects of the invention, this preferred proportion of chitosan, or derivative or salt thereof, in the composition of matter is mainly dictated by the capacity for dissolution or suspension of the active ingredient by the second component and the acidic environment, when the composition is placed in an aqueous liquid. The content of chitosan, or of derivatives or salts thereof, has to be sufficiently low, compared to the content of effervescing components in the composition of matter, for dissolution to occur. The percentage referred to above is thus the percentage of chitosan in relation to effervescing components. Surprisingly, it has been found by the present inventors that the relation between the quantity of effervescence-generating components and chitosan, or derivatives or salts thereof, is critical for the dissolution of the composition in an aqueous liquid. As stated above, most chitosan qualities will not dissolve without vigorous stirring, even in large amounts of aqueous liquid and after long times. This also holds true if the proportion of chitosan is too large in relation to the quantity of effervescing components. The dissolution rate of chitosan, or derivatives or salts thereof, in the composition of matter according to the invention thus depends on efficient mixing caused by release of CO₂ from the effervescent components, as well as on the final pH of the solution, as described in detail below.

If chitosan derivatives or salts are used that are more easily dissolved than chitosan itself, the percentage thereof may be increased. The same is true for chitosan, or derivatives or salts thereof, of different molecular weights, low-molecular weight qualities being more easily dissolved or suspended.

The preferred quality of the chitosan, or derivative or salt thereof, used in the composition of matter according to the invention depends on the specific area of use. This in turn will influence the concentration of chitosan, or derivative or salt thereof, that is preferred.

To obtain maximum anti-microbial efficiency, in those embodiments of the invention where this is desired, it is preferred that the chitosan, or derivative or salt thereof, has a degree of deacetylation of no less than about 50%, preferably no less than about 80% and particularly no less than about 85%. However, an upper limit of the deacetylation degree of about 95% is preferred, mainly due to practical and economic aspects of the preparation of chitosan, or derivative or salt thereof. Thus, a preferred composition of matter according to the invention comprises chitosan, or derivative or salt thereof, having a deacetylation degree within the range from about 85% to about 95%, but the upper limit of 95% may be exceeded by compositions that still come within the scope of the present invention. This may occur for example if an economical process of obtaining chitosan of such high degree of deacetylation is made available. Then, chitosan having a deacetylation degree of up to 99% or more may be obtainable, and may well be used in compositions according to the present invention.

The viscosity of an aqueous solution of a certain concentration of chitosan, or derivative or salt thereof, can be modified by using qualities of chitosan, its derivatives or salts thereof with different weight average molecular weights ({overscore (Mw)}), In the present invention, chitosan, or derivative or salt thereof, with a molecular weight of between 1 kDa and 2000 kDa is preferred.

The preferred particle size of the chitosan, or derivative or salt thereof, used is less than 850 μm, more preferably less than 250 μm (60 mesh). If chitosan, or derivative or salt thereof, of another particle size is used, ox if the molecular weight of the chitosan, or derivative or salt thereof, is such that dissolution of particles is difficult, the particles may be ground to a smaller size prior to use.

In a composition of matter according to the invention, said second component is preferably a carbonate, e g selected from alkali metal carbonates, alkali metal bicarbonates, alkaline earth metal carbonates, alkaline earth metal bicarbonates, ammonium carbonate, and ammonium bicarbonate.

Said second component has the capacity to release CO₂ in an acidic environment. This acidic environment may be provided as an aqueous solution with a low pH, e g an acetic acid solution, in which the composition of matter is placed, In preferred embodiments, however, release of CO₂ is obtained through the use of a third component of the solid composition, which is selected from solid acids and mixtures thereof.

In such embodiments, said second and third component of the composition of matter according to the invention can be regarded as an "effervescent couple". The effervescent couple thus comprises at least one component capable of releasing CO₂ in an acidic environment (the second component of the composition of matter) and at least one solid acid (the third component), preferably a solid organic acid. The couple renders effervescence upon mixing with an aqueous solution, as the components of the couple combine to produce carbon dioxide. The effervescing action also aids in mixing the other ingredients of the composition to achieve even dispersion and solubilisation throughout the solution.

In those embodiments of the invention that employ a solid acid, or mixture of solid acids, as a third component, it is preferred to use a solid organic acid, or mixtures of solid acids comprising at least one solid organic acid. Preferably, this is a weak organic acid that provides a certain buffering effect resulting in a less varying pH in a solution or suspension prepared by dissolution or suspension of the solid composition according to the invention. For the purposes of preparing a solution or suspension for use on the teats of lactating animals, a non-toxic, mono-carboxylic acid, e g a non-toxic α-hydroxy acid, is preferred, glycolic acid being the most preferred for this application, In other applications, the preferred solid organic acid may be an α-hydroxy acid or an acid other than α-hydroxy acids, including ascorbic acid. In most biological applications, the solid acid will need to exhibit properties such as non-toxicity and pharmaceutical acceptability. The pK_a of the solid acid is preferably below 7, a pK_a below 5 being even more preferred.

A particularly preferred composition of matter according to the invention is constituted by the active component being selected from chitosan, its derivatives and salts thereof, the second component being an alkali metal bicarbonate, and the composition further comprising a third component which is glycolic acid.

In the composition of matter according to the invention, the contents of acid thereof is preferably in stoichiometric excess over the contents of said second component.

Where the active component is an acid addition salt of chitosan and the composition contains a solid acid, or mixture of solid acids, as third component, said stoichiometric excess is based on said third component together with the acid of addition.

Where the composition of matter according to the invention contains chitosan as such as active principle and a solid acid, or mixture of solid acids, as third component, said stoichiometric excess refers to the contents of the third component over the second component.

The composition of matter, according to those embodiments of the invention that contain a solid acid, or mixture of solid acids, as third component, preferably has an acid content such that, when the composition is dissolved or suspended in the appropriate amount of aqueous liquid, the pH of the solution or suspension is below about 7, so that the chitosan of the composition is readily dissolved. More preferably, the pH value is in the range of from about 2 to about 6.8, the lower limit being dictated mainly by the desired properties of the solution or suspension. For applications wherein the solution or suspension is to be applied to the skin of an animal or human subject, the pH range is even more preferably from about 4 to about 6.8, the lower limit here being dictated by the sensitivity of the area to which the solution or suspension is to be applied.

When the composition is dissolved or suspended in the appropriate amount of liquid, the pH of the solution or suspension can optionally be further stabilised by use of a pH buffering system, which in certain applications of the present invention will need to be non-toxic and pharmaceutically acceptable. Examples of preferred buffering systems include the acetic acid system and buffer systems of other monovalent acids, e g lactic acid.

The acidic pH of the liquid provides a suitable environment for dissolution or suspension of chitosan, or of a derivative or salt thereof, as well as a suitable environment for CO₂ release from the second component. Inventively, these two effects operate in a synergistic manner to facilitate the dissolution or suspension of chitosan, or derivative or salt thereof, in the liquid.

The composition of matter according to the invention may additionally contain heparin, heparan sulfate, dextran sulfate or another negatively charged polysaccharide or polymer. It may also be preferred to include neutral polymers, e g cellulose, in the composition of matter according to the invention, since such polymers may confer desired properties to a solution or suspension made from the composition, in terms of e g improved clarity or viscosity.

The composition of matter according to the present invention can be presented in different forms, e g powder, granules, pellets, capsules or tablets of suitable size, prepared by standard methods well known to the skilled person. An additional component of the composition, e g any of the negatively charged polysaccharides mentioned in the previous paragraph, may be added as a separated coating around a core consisting of the main components of the composition of matter, forming a dragée, or as a part of a tablet containing more than one compartment.

The composition of matter according to the present invention may optionally further comprise pharmaceutically acceptable excipients known to the skilled person, e g binders, diluents, surfactants, lubricants, disintegrants, anti-microbial agents, detergents and colouring agents.

The composition of matter according to the present invention is preferably kept in moisture-proof or airtight packages or containers, e g welded aluminum containers, etc. Transportation of products in a dry form and in moisture-proof packets makes it more difficult to contaminate the product. Further, such compositions are much less expensive to transport than compositions in liquid form. In many cases, the effectiveness of active ingredients is prolonged in a dry, rather than liquid, state due to increased stability of the ingredients in the dry state.

The composition of matter according to the invention is thus especially practical when it is used for the preparation of solutions or suspensions, which retain their activity for only a short time after preparation thereof, since said solutions or suspensions may be prepared shortly or even immediately before use,

According to one preferred embodiment, the composition of matter according to the present invention is kept in one separate, moisture-proof container, while an effervescent composition of matter comprising heparin, heparan sulfate, dextran sulfate or another negatively charged polysaccharide or polymer is kept in another separate container. Thus, the contents of the two containers may be used simultaneously or at separate instants. Another possibility is the provision, in such a second, separate container, of a liquid, e g glycerol, that confers desired properties, e g a skin conditioning effect, to the resulting solution or suspension.

The composition of matter according to the present invention can be used as a medicament. In particular, the composition of matter according to the present invention can be used for the manufacture of an aqueous solution or suspension for treatment of dermal wounds in mammals including man. Furthermore, the composition of matter according to the present invention can advantageously be used for the manufacture of an aqueous solution or suspension for prophylactic or wound-healing treatment of mastitis in lactating animals.

The present invention also relates to a method for treatment of a mammal suffering from a dermal wound, which method comprises the steps of: