A PROCESS FOR THE PREPARATION OF A FREE FLOWING, HOMOGENEOUS, IODOPHOR CONTAINING WOUND POWDER

Abstract: A process for the preparation of a free flowing, iodophor containing wound powder in which a finely divided sugar is sprayed, in a fluidised bed granulator, with a solution of the iodophor in a solvent comprising water and an alkyl alcohol having a boiling point (at 760mm Hg) below 100◊C. Preferably the sugar is sucrose, the iodophor is povidone iodine and the alcohol is ethanol. The process allows the formation of a free flowing, homogeneous wound powder that is well tolerated when applied to wounds.

Description: This invention relates to a process for the preparation of a free flowing, homogeneous, iodophor containing wound powder. Iodophors are physiologically acceptable complexes of iodine with organic polymers, in which the germicidal and microbiocidal activity of elemental iodine is maintained. In the main, they are water-soluble. Amongst the most effective (microbiocidally) of these iodophors are the complexes of iodine with non-ionic, non-detergent (non-surface active) organic polymers, such as polydextrose or, which is most widely used, polyvinylpyrrolidone (povidone). Iodophors, for example polydextrose iodine and povidone iodine, may be dispensed in various kinds of semi-solid and liquid pharmaceutical preparations, such as solutions, ointments and aerosols. In the treatment of wounds, however, a powder formulation would have the advantage of ease of application, the powder simply being sprinkled into the wound. For the best results, such a powder should be both homogeneous and free flowing. Unfortunately, most iodophors, especially the "non-ionic" variety (e.g. polydextrose iodine and povidone iodine) are amorphous, hygroscopic and non-free flowing powders. They can be transformed into free flowing powders by the addition of glidants, such as talc, but, although talc is widely used as a dusting powder and is an innocuous substance when applied to the intact skin, it may induce severe granulomatous reactions, when introduced into wounds or when employed during surgery, and so it cannot be considered as an ingredient in wound powders. There is therefore a need for a wound powder containing an iodophor, but not talc, that is free flowing and homogeneous. It is one object of the present invention to provide a process for the preparation of such a wound powder. Other objects and advantages of the present invention will become apparent from the following detailed description thereof. According to the present invention there is provided a process for the preparation of a free flowing, iodophor containing wound powder comprising spraying a finely divided sugar in a fluidised bed granulator with a solution of the iodophor in a solvent comprising water and an alkyl alcohol having a boiling point, at 760mm Hg, below 100¤C. The sugar employed in the present process may be any solid saccharide that can be finely divided enough to form a free flowing wound powder in the present process. Suitable sugars include sucrose, dextrose, maltose, fructose and lactose, with sucrose being particularly preferred. The finely divided sugar may have any range of particle size that allows the formation of a finely divided wound powder by the present process. Preferably, however, all of the sugar will have particle sizes of 250 µm or less (60 mesh sieve), whilst at least 90% (by wt.) of the sugar will have particle sizes of 150 µm or less (100 mesh sieve). The iodophor must form a free flowing powder in the present process. The most suitable iodophors are complexes of iodine with non-ionic, non-detergent organic polymers, especially polydextrose iodine or, which is particularly preferred, povidone iodine. Povidone iodine is a well known iodophor that is a highly effective germicide, providing a broad spectrum of microbiocidal action against virtually all microbes. It may be prepared by any of a number of known routes, see, for example, European Published Applications No. EP-A-120301A and EP-A-6340A and British Patent No. GB-A-1580596. Polydextrose is a non-nutritive polysaccharide, prepared by the condensation polymerisation of saccharides in the presence of polycarboxylic acid catalysts, under reduced pressure. Polydextrose is described in US Patents No. US-A-3766105 and US-A-3786794, and is available from Pfizer Inc., New York. Commercially available polydextrose polymer is a low molecular weight, water-soluble, randomly bonded polymer of glucose containing minor amounts of sorbitol end groups and citric acid residues attached to the polymer by mono- and di-ester bonds. The number average molecular weight of this commercially available material is 1,500, ranging from 160 to 20,000. When polydextrose polymer is combined with elemental iodine, preferably in the presence of an alkali metal iodide, the resultant polydextrose iodine complex is formed. This complex is a tan-to-amber coloured product which melts between 90¤C and 130¤C to form a red liquid. Polydextrose iodine powder is highly soluble in water and at room temperature results in a reddish brown coloured aqueous solution. The amount of iodine incorporated in the iodophors used in the present wound powder will be determined by, amongst other factors, the amount of iodophor present in the wound powder and the required antibacterial strength of the powder. Preferably, iodine will constitute between 1 and 20% (by wt.), especially between 2 and 15% (by wt.) of the iodophor dry weight. The concentration of the iodophor in the present wound powder will depend on the antibacterial strength required. In addition, iodophor concentration will be determined by, amongst other factors, the iodophor employed, the propensity of the iodophor to cause irritation and the amount of iodine in the iodophor. Thus, the wound powder preferably contains enough iodophor to afford a concentration of available (titratable) iodine within the powder of between 0.1 and 2% (by wt.), especially between 0.2 and 1.5% (by wt.). Thus, a wound powder employing povidone iodine, with 10% (by wt.) available iodine, as the iodophor, would preferably contain between 1 and 20%, especially 2 and 15%, (by wt.) of povidone iodine. Any alkyl alcohol having a boiling point, at 760mm Hg, below 100¤C, may be employed in the present process. Alkyl alcohols, such as methanol, ethanol and isopropanol, having a boiling point (at 760mm Hg) below 90¤C are preferred, with ethanol being particularly preferred. Any ratio of alcohol to water in the present solvent that produces a free-flowing wound powder by the present process may be employed. The ratio is chosen so that the evaporation of the solvent is neither too slow nor too rapid. If the evaporation were too slow it would lead to sticky products, whereas, if it were too rapid, it would lead to non-homogeneous products. The present inventor has found that the most effective solvent for use in the present process contains between 70% and 85% (v/v) alkyl alcohol and between 30% and 15% (v/v) water, especially between 78% and 80% (v/v) alkyl alcohol and between 22% and 20% (v/v) water. The iodophor solution may also contain selected pharmaceutical excipients that will facilitate the removal of the subsequent wound powder from a wound for cleansing or inspection purposes. These excipients are preferably free flowing powders and water soluble. Examples include polyethylene glycol and certain celluloses, e.g. carboxyalkylcelluloses and hydroxyalkylcelluloses. The present process may be conducted at any temperature that leads to a free-flowing wound powder. In a preferred embodiment of the present invention, the process is conducted at a temperature between 30¤C and 50¤C, especially at about 40¤C. It is an important feature of the present process that the pH of the subsequent iodophor/sugar combination may be adjusted to a value that is well tolerated in the treatment of wounds. Well tolerated iodophor/sugar powders will produce 50% (w/v) aqueous solutions that have a pH between 3.0 and 7.0, especially between 4.0 and 6.0. This adjustment may be effected by the addition of a base to the iodophor solution prior to spraying. In a particularly preferred embodiment of the present process, a solution of povidone iodine in aqueous ethyl alcohol is neutralised with sodium hydroxide solution. In this embodiment, once the process is complete, a 50% (w/v) aqueous solution of the subsequent povidone iodine/sucrose powder has a pH between 4.5 and 5.0. It is therefore well tolerated when sprayed on open wounds. Such an adjustment is not possible when the wound powder is prepared by conventional granulation methods or if an iodophor/sugar mixture is sprayed with dilute alcohol in a fluidised bed granulator. In these cases, a 50% (w/v) aqueous solution of a subsequent povidone iodine/sucrose powder has a pH value of 1.5. The powder would therefore not be well tolerated when sprayed on an open wound. The production of a free flowing wound powder by the present process is surprising because (a) When conventional granulation techniques are employed, that is mixing an iodophor (especially povidone iodine) and a sugar (especially sucrose) in a suitable granulator with the aid of an aqueous alcohol, subsequent drying and sieving produces a powder of insufficient homogeneity and fineness for wound treatment, and (b) Furthermore, when a mixture of an iodophor (especially povidone iodine) and a sugar (especially sucrose) are sprayed with an aqueous alcohol in a fluidised bed granulator the product is once again non-homogeneous and too coarse. Wound powders prepared by the present process may be dispersed freely onto skin or wounds to the skin. In order to facilitate the use of the present wound powders, however, they may be coated or admixed with other ingredients, such as free flowing powders, that are adapted to improve the therapeutic nature of the powder. Examples of such additional powders include (i) Polyethylene glycol, a carboxyalkylcellulose or a hydroxyalkylcellulose. These facilitate the removal of a wound powder of the present type from a wound when it (the wound) has to be cleaned or inspected, (ii) Zinc oxide. This material possesses mild astringent and antiseptic properties in its own right and therefore acts so as to aid the healing of skin wounds. Zinc oxide also improves the powder flow characteristics of the present wound powders. Wound powders of the present invention are conveniently dispersed or sprinkled onto an area of skin to be treated from a bottle having a plurality of small holes at its outlet, such as the type of bottle that is generally used for the application of talcum powder. Preferably the bottle used is made of a flexible or resilient material so that the bottle may be squeezed to help expel the powder. The present process and wound powders prepared by the present process will now be described by way of example only. Preparation of Polydextrose Iodine Powder Polydextrose (0.84 kg) was dissolved in warm water (10 litres). A solution of iodine (103gm) and ammonium iodide (57gm) in ethanol (3 litres) was added. After stirring for 1hr. at 20¤C, the solvents were evaporated, under reduced pressure, and the residue was pulverised. Example 1 Finely divided sucrose (4.5kg) was brought into a fluidised bed granulator at 40¤C. Povidone iodine (0.5kg) was dissolved in a mixture of 96% ethanol (3.5 litres) and distilled water (0.75 litres). This solution was neutralised with 4N sodium hydroxide solution and then sprayed onto the sucrose powder at a rate of 50mlmin⁻¹ and at a spraying pressure of 4 bar (4 x 10⁵ Pascals). The granulate obtained was sieved through a 60 mesh sieve in order to remove any coarse particles. The yellow-brown, free-flowing, homogenous powder has a particle size distribution as follows: Example 2 The process of Example 1 was repeated except that polydextrose iodine (0.4kg) replaced the povidone iodine. Example 3 The process of Example 1 was repeated except that finely divided lactose (4.5kg) replaced sucrose as the sugar. Example 4 The process of Example 1 was repeated except that finely divided dextrose (2.3kg) replaced sucrose as the sugar. Example 5 Finely divided sucrose (4.8kg) was brought into a fluidised bed granulator at 40¤C. Povidone iodine (0.6kg) was dissolved in 96% ethanol (3.5 litres) and a solution of polyethylene glycol 6000 (0.6kg) in distilled water (0.5 litres) was added. This solution was neutralised with 4N sodium hydroxide to pH 7.0 and then sprayed onto the sucrose powder at a rate of 50ml min⁻¹ and at a spraying pressure of 4 bar (4 x 10⁵ Pascals).

Claims: A process for the preparation of a free flowing, iodophor containing wound powder comprising spraying a finely divided sugar in a fluidised bed granulator with a solution of the iodophor in a solvent comprising water and an alkyl alcohol having a boiling point, at 760mm Hg, below 100¤C. A process according to claim 1 characterised in that the sugar comprises dextrose, maltose, fructose, lactose or, preferably, sucrose. A process according to either claim 1 or claim 2 characterised in that all of the sugar has a particle size of 250 µm (microns) or less and in that 90% (by wt) of the sugar has a particle size of 150 µm (microns) or less. A process according to any one of claims 1 to 3 characterised in that the iodophor comprises polydextrose iodine or, preferably, povidone iodine. A process according to any one of claims 1 to 4 characterised in that the amount of iodophor in the solvent is sufficient to give a wound powder containing between 0.1 and 2.0% (by wt), especially between 0.2 and 1.5% (by wt), available iodine. A process according to any one of claims 1 to 5 characterised in that the alkyl alcohol comprises methanol, isopropanol or, preferably, ethanol. A process according to any one of claims 1 to 6 characterised in that the solvent comprises between 70 and 85% (v/v) alkyl alcohol and between 30 and 15% (v/v) water, preferably between 78 and 80% (v/v) alkyl alcohol and between 22 and 20% (v/v) water. A process according to any one of claims 1 to 7 characterised in that , before being sprayed onto the finely divided sugar, the pH of the iodophor solution is adjusted such that a 50% (w/v) aqueous solution of the subsequent wound powder has a pH between 3.0 and 7.0, preferably between 4.0 and 6.0. A process according to any one of claims 1 to 8 characterised in that the wound powder obtained is subsequently coated or admixed with a free flowing powder selected from polyethylene glycol, a carboxymethylcellulose, a hydroxyalkylcellulose or zinc oxide.

Inventors: JAUW, TJOE HANG
Applicants: EUROCELTIQUE SA
Application year: 1986
Main classification: A61K33
IPC codes: A61K9, A61K31, A61P17, A01N59, A61K47, A61K33