GB2624181A

GB2624181A - Oral lozenges

Info

Publication number: GB2624181A
Application number: GB2216614.4A
Authority: GB
Inventors: Rahman Ayesha; Mohamed Zaid Norhaziland
Original assignee: Of Wolverhampton, University of; Wolverhampton, University of
Current assignee: Of Wolverhampton, University of; Wolverhampton, University of
Priority date: 2022-11-08
Filing date: 2022-11-08
Publication date: 2024-05-15
Also published as: GB202216614D0; WO2024100396A1

Abstract

An oral lozenge comprising 0.005-4% w/w chlorhexidine or a salt thereof and 2-80% w/w of polyol, wherein the polyol comprises xylitol, sorbitol, erythritol or maltitol. A use of the lozenge for inhibiting oral biofilm formation, treating or preventing gingivitis and/or treating or preventing dental caries and a method of preparing an oral lozenge comprising blending a mixture comprising 0.005-4% chlorhexidine or a salt thereof and 2-80% polyol, wherein the polyol comprises xylitol, sorbitol, erythritol or maltitol, and compressing the blend into a lozenge are also included. The polyol may be xylitol. The lozenge may comprise 0.05-4% chlorhexidine, preferably 0.05-2% or more preferably 0.05-1%. The lozenge may comprise 0.005-0.1% chlorhexidine. The lozenge may comprise 2-40% polyol, preferably 2-15%. The lozenge may comprise 40-80% polyol. The chlorhexidine may be chlorhexidine diacetate. The lozenge may have a hardness from 9-14 kp or a friability of 0.07-1.5%. The lozenge may be compressed with a force of 4 tonnes. The lozenge may further comprise a menthol flavouring agent, an orange flavour, a silicified microcrystalline cellulose hygroscopic agent and a magnesium stearate lubricant.

Description

ORAL LOZENGES

FIELD OF THE INVENTION

Embodiments of the present invention relate to oral lozenges. In particular, they relate to oral lozenges for use in inhibiting oral biofilm formation, preventing or treating gingivitis and/or preventing or treating dental caries.

BACKGROUND TO THE INVENTION

Dental plaque is an oral microbial biofilm that is found on exposed tooth surfaces in the mouth. Biofilms are communities of microorganisms, encapsulated in an extracellular matrix of polymers, that live at interfaces. While biofilms may grow at liquid interfaces or liquid/gas interfaces, they are typically attached to a biotic or abiotic surface that interfaces with liquid or gas. Most bacteria can form biofilms, but biofilms do not solely comprise bacteria and may include algae, archaea, fungi, and protozoa. The extracellular matrix is made up of varying combinations of polysaccharides, proteins, and nucleic acids.

Over time, dental plaque is a causal agent of dental caries. Dental caries is the localized destruction of dental hard tissues by acidic by-products from dental plaque containing acid-producing bacteria.

Streptococcus mutans (NTCC 10449) initiates dental biofilm formation on the surfaces of teeth by producing the extracellular matrix and is thus a primary etiologic agent in the development of dental caries.

Dental plaque is also a common cause of gingivitis, which is a form of gum disease.

Chlorhexidine is a bioactive compound known to disrupt Streptococcus mutans and thus the formation of biofilms such as dental plaque. Chlorhexidine is therefore a potential treatment for dental caries and gingivitis.

Oral lozenge formulations including chlorhexidine are known. However, to achieve a minimum inhibitory concentration (MIC) or a minimum lethal concentration (MLC), such oral lozenges comprise a quantity of chlorhexidine sufficiently high to also cause teeth staining, which is an undesirable side effect of chlorhexidine. Such lozenges generally comprise sugar, such as glucose, fructose, sucrose, and/or maltodextrin to aid taste and texture. However, sugar can increase bionm formation thereby counteracting the effect of chlorhexidine.

There is, therefore, a need to provide oral lozenges which have improved performance and minimize teeth staining.

BRIEF DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION

According to a first aspect of the present disclosure, there is provided an oral lozenge, the oral lozenge comprising: 0.005 to 4% w/w chlorhexidine or a salt thereof; and 2 to 80% w/w polyol, wherein the polyol comprises xylitol, sorbitol, erythritol or maltitol.

The polyol may be xylitol. The polyol may consist of xylitol.

The oral lozenge may comprise from 0.05 to 4% w/w chlorhexidine or a salt thereof, or may comprise from 0.05 to 2% w/w chlorhexidine or a salt thereof, or may comprise from 0.05 to 1% w/w chlorhexidine or a salt thereof, or may comprise from 0.05 to 0.1% w/w chlorhexidine or a salt thereof, or may comprise from 0.005 to 0.1% w/w chlorhexidine or a salt thereof, or may comprise from 0.005 to 0.05% w/w chlorhexidine or a salt thereof.

In some examples, the oral lozenge may comprise from 2 to 40% w/w polyol, or may 30 comprise from 2 to 15% w/w polyol, or may comprise from 2 to 5% w/w polyol. In other examples, the oral lozenge may comprise from 40 to 80% polyol, or may comprise from 50 to 75% w/w polyol, or may comprise from 55 to 70% w/w polyol.

Possibly, the oral lozenge comprises chlorhexidine in the form of a salt which is chlorhexidine diacetate, chlorhexidine dihydrochloride, chlorhexidine digluconate, chlorhexidine gluconate, chlorhexidine phosphanilate, or mixtures thereof. The oral lozenge may comprise chlorhexidine in the form of a salt which is chlorhexidine diacetate.

Possibly, the oral lozenge further comprises: flavouring agent; and/or silicified methylcellulose, and/or magnesium stearate.

The oral lozenge may have a hardness of from 2 to 15 kp, or may have a hardness of from 9 to 14 kp, or may have a hardness of about 11.5 kp.

The oral lozenge may have a friability of from 0.05 to 2 %, or may have a friability of from 0.07 to 1.5 %, or may have a friability of less than 1 %.

The unit weight of the oral lozenge may be from 100 mg to 500 mg, and may be about 500 mg.

The oral lozenge may be sugar free.

Possibly, the oral lozenge is for use in inhibiting oral biofilm formation, treating or preventing gingivitis and/or treating or preventing dental caries.

The oral lozenge may dissolve in 15 to 30 minutes upon administration to the oral cavity.

According to a second aspect of the present disclosure, there is provided a method of 30 preparing an oral lozenge according to any of the preceding paragraphs, the method comprising: blending a mixture comprising from 0.005 to 4% w/w chlorhexidine or a salt thereof and from 2 to 80% w/w polyol, wherein the polyol comprises xylitol, sorbitol, erythritol or maltitol; and compressing the blend into an oral lozenge.

The method may comprise applying a compression force on the blend of from 2 to 8 tonnes, or may comprise applying a compression force on the blend of 4 tonnes.

For a better understanding of various examples that are useful for understanding the detailed description, reference will now be made by way of example only and with reference to the accompanying figures.

BRIEF DESCRIPTION OF THE FIGURES

Figure 1 depicts an evaluation of the thickness of tablet lozenges at different compression forces; Figure 2 depicts an evaluation of the diameter of tablet lozenges at different compression forces; Figure 3 depicts the drug release of lozenges made at four different compression forces; Figure 4 depicts an evaluation of drug release of CHX lozenge tablets according to stability study for 1, 30, 60, 90 and 180 days; Figure 5 depicts a time kill curve of streptococcus mutans exposed to CHX, Xylitol, and Xylitol-CHX; Figure 6 depicts biofilm formation of streptococcus mutans at 72 hours at a xylitol concentration of 2, 5, 10, 20 and 40% and a CHX concentration of 0.1, 0.5, 1, 2 and 4 pg/ml; Figure 7 depicts percentage EPS production in streptococcus mutans biofilms during inhibition assay at 72 hours with 2%, 5% and 10% of xylitol treated with 0.5 and 1.0 pg/ml CHX concentration; and Figure 8 depicts biofilm formation of streptococcus mutans at 72 hours at a sorbitol concentration of 2, 5, 10, 20 and 40% and a CHX concentration of 0.1, 0.5, 1, 2 and 4 pg/m I.

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS OF THE INVENTION

Examples of the disclosure provide an oral lozenge. The oral lozenge comprises from 0.005 to 4% w/w chlorhexidine or a salt thereof and from 2 to 80% w/w polyol. The polyol comprises xylitol, sorbitol, erythritol or maltitol.

An oral lozenge is a solid, single-dose preparation intended to be sucked and held in the mouth, i.e., the oral cavity. Accordingly, an oral lozenge is a solid dosage form for release of active agents. Although the time of lozenge dissolution in the oral cavity is about 15 to 30 minutes, this depends on the patient as the patient controls the rate of dissolution and absorption by sucking the lozenge until it dissolves. Accordingly, oral lozenges are orally dissolving lozenges. An oral lozenge may also be referred to as a lozenge, lozenge tablet or tablet in the present disclosure.

In some examples, the oral lozenge may further comprise a flavouring agent, and/or a hygroscopic agent such as silicified methylcellulose, and/or a lubricant such as magnesium stearate. The oral lozenge may further comprise chelating agents, antioxidants, and/or colourants.

The oral lozenge may be sugar free. In such examples, the oral lozenge does not comprise any sugar.

An example formulation of an oral lozenge according to the disclosure is provided in Table 1 below. Unless otherwise specified all parts and percentages set forth herein are weight percentages (% w/w) based on the total weight of the oral lozenge being described.

Table 1

Excipient (general) Excipient (specific) El (To w/w) Synergist and Filler Xylitol 65.5 (327.5 mg) Antibacterial (antiseptic) Chlorhexidine (CHX) 4 (20 mg) agent Flavouring agent Menthol 4 (20 mg) Flavouring agent Orange flavour 1 (5mg) Hygroscopic agent Silicified microcrystalline 25 (125 mg) cellulose (SMCC) Lubricant Magnesium stearate 0.5 (2.5 mg) Total 100 (500 mg) Excipients Synergist and Filler In examples of the disclosure, oral lozenges comprise a polyol, wherein the polyol comprises xylitol, sorbitol, erythritol or maltitol. The oral lozenge comprises from 2 to 80% w/w polyol In example El the polyol, xylitol, has a dual functionality, acting as a filler and a synergist. A filler binds the mixture together and aids in solidifying the lozenge. As described in more detail below, a synergist enhances the effectiveness of the antimicrobial agent chlorhexidine or salts thereof.

In other examples, the polyol may instead be sorbitol, erythritol or maltitol. Accordingly, the synergist may comprise xylitol, sorbitol, erythritol or maltitol. The synergist may be selected from the group consisting of xylitol, sorbitol, erythritol or maltitol.

The filler may also comprise xylitol, sorbitol, erythritol or maltitol. The filler may be selected from the group consisting of xylitol, sorbitol, erythritol or maltitol.

The filler and the synergist may be the same material, i.e., identical. In such examples, the oral lozenge may comprise from 40 to 80% w/w polyol, or from 50 to 75% w/w polyol, or from or from 55 to 70% w/w polyol.

In other examples, the filler and the synergist may be different materials. Accordingly, in some examples the synergist may comprise xylitol, sorbitol, erythritol or maltitol, and the filler may comprise a different material, such as a different polyol, polyethylene glycol (PEG) 6000 and 8000, calcium phosphate, calcium sulphate, calcium carbonate, lactose, glucose, sucrose, microcrystalline cellulose, or other cellulose derivatives. In such examples, the amount of selected (synergistic) polyol present may be from 2 to 40 % w/w, or may be from 2 to 25 % w/w, or may be from 2 to 15 % w/w, or may be from 5 to 20% w/w, or may be from 2 to 10 % w/w, or may be from 2 to 5 % w/w, or may be less than 5 % w/w. In such examples, the amount of filler present (the filler being a different material from the selected synergistic polyol) may be from 20 to 80 % w/w, or may be from 30 to 70 % w/w, or may be from 40 to 60% w/w.

Antibacterial (antiseptic) agent Chlorhexidine (CHX) In examples of the disclosure, oral lozenges comprise chlorhexidine (CHX).

Chlorhexidine is an antibacterial (antiseptic) agent which is used in oral care compositions. Chlorhexidine is a bis-biguanide with the chemical name N,N"-bis(4-chloropheny1)-3,12-diimino-2,4,11,13-etraazatetradecanediim idam ide): It is available as a white or yellowish material in both free-base and stable salt forms. There are several salt forms which include CHX diacetate (CHA), CHX dihydrochloride 5 (CHU), CHX digluconate (CHDG), CHX gluconate (CHG) and CHX phosphanilate (CHP).

The oral lozenge comprises from 0.005 to 4% w/w chlorhexidine or a salt thereof.

In some examples, the oral lozenge comprises 0.05 to 4% w/w chlorhexidine or a salt thereof, or from 0.05 to 2% w/w chlorhexidine or a salt thereof, or from 0.05 to 1% w/w chlorhexidine or a salt thereof, or from 0.05 to 0.1% w/w chlorhexidine or a salt thereof, or from 0.005 to 0.1% w/w chlorhexidine or a salt thereof, or from 0.005 to 0.05% w/w chlorhexidine or a salt thereof.

Chlorhexidine or a salt thereof may be referred to as drug, active agent, or active pharmaceutical ingredient (API) in the present disclosure.

Flavouring agent A flavouring agent is a substance used to give a different, stronger, or more agreeable taste to the oral lozenge.

In some examples, the oral lozenge comprises one or more flavouring agents, such as orange flavour, menthol, peppermint, spearmint, cinnamon, wintergreen oils, or methyl salicylate derivatives. Flavouring agents may be used individually or in combination. The oral lozenge may comprise from 0.05 to 10% w/w of a flavouring agent, or from 0.5 to 8% w/w of a flavouring agent, or from 1 to 5% w/w of a flavouring agent.

Hygroscopic agent A hygroscopic agent affects disintegration and drug dissolution due to diffusion of the media into the oral lozenge matrix. In some examples, such as El, the lubricant comprises magnesium stearate.

The oral lozenge may comprise from 5 to 40% w/w of a hygroscopic agent, or from 10 to 35% w/w of a hygroscopic agent, or from 15 to 30% w/w of a hygroscopic agent.

Lubricant In some examples, such as El the oral lozenge comprises a lubricant such as magnesium stearate.

The oral lozenge may comprise from 0.01 to 5% w/w of a lubricant, or from 0.05 to 2% w/w of a lubricant, or from 0.1 to 1% w/w of a lubricant.

Preparation of lozenges using direct compression Excipients comprised in example oral lozenges are listed in Table 1 above.

An example preparation is as follows. All the excipients were blended for 5 minutes in a V-shaped powder blender (CapsuICNO) except silicified microcrystalline cellulose and magnesium stearate. Then silicified microcrystalline cellulose was added into the mixtures and blended for another 3 minutes. Finally, magnesium stearate was added to the mixture and blended for another 1 minute.

The steps for manufacturing of lozenge tablets by a direct compression method are as follows: 1. weighing, 2. blending, 3. lubrication, and 4. compression.

The samples of each excipient were accurately weighed as in Table 1 and then compressed on 10 mm punch and die using a single-punch manual tableting machine (Globpharma, USA) at a fixed pressure of 2000 psi.

S Method of physico-chemical analysis of lozenge tablets Thickness and diameter The thickness and diameter of lozenges were determined using electronic digital 10 Vernier callipers (MSC-Limited, U.K). Ten oral lozenges from each batch were used and average values were calculated Hardness The hardness of the lozenges was determined by using hardness tester (Varian, VK 200, Benchsaver Series, U.K) where the force required to break the lozenges were noted. Ten oral lozenges were selected, for every batch of formulation to analyse and data were recorded.

Weight variation The weight variation was conducted by weighting ten lozenges individually and calculating the average weight and comparing the average lozenges weight to the average value.

Friability Twenty lozenge tablets were weighed and placed in the friabilator (Charles Ischi AG, AE-1, U.K.), and rotated 100 times at 25 rpm for 4 minutes. After revolutions the tablets 30 were dedusted and weighed again. The percentage friability, was calculated for analysis using below equation Wi -Wf Friability - x 100

WI

where WI, is the initial weight and Wf is the final weight.

Experiments conducted on oral lozenges Oral lozenge compression at different forces Excipients were blended as outlined above. The resultant blend was directly compressed using a single-punch tablet machine with size 10mm flat faced die at different compression forces of 4, 6 and 8 tonnes.

Oral lozenge erosion/swelling To evaluate the effect of compression force on each formulation, lozenge tablet diameter and thickness was recorded. The tablets were then placed in a small container with a lid which contained 18 ml of distilled water at room temperature. At various time intervals (0, 5, 15 and 40 min), diameter and thickness of tablets were measured by using electronic digital Vernier callipers. The percentage increase in erosion/swelling of each tablet due to water uptake was calculated using the following equation: Mt-MO Erosion = x 100

MO

where Mt is the diameter of tablet at time t and Mo is the diameter of tablet at time 0. The experiments were performed in triplicate for each time point. Fresh samples were used for each time point.

Dissolution study Dissolution testing was performed to study in-vitro dissolution and the rate at which the drug (chlorhexidine or a salt thereof) is released from lozenge. A USP dissolution apparatus II (paddle method) was used with a rotational speed of 100 rpm. The dissolution testing system comprised of a VK7010 dissolution apparatus (Varian, USA) and an automated sampling manifold (Varian, UK). The dissolution test was performed according to the USP Pharmacopoeia. The dissolution media consisted of 900 ml of distilled water equilibrated to 37°C ± 0.5°C. 5 ml of samples were withdrawn from the dissolution medium and replaced with the same volume of fresh media using a syringe at intervals of 2 for 20 minutes. The absorbances of CHX were recorded using a UV spectrophotometer at A254 nm by NovaSpec II, Pharmacia Biotech, U.K. Three tablets were tested for each formulation.

Stability Study Long term stability studies were conducted by placing the lozenges in individual foil and placed in airtight dark container in the desiccator according to ICH guidelines at 25±2°C and relative humidity at 60±5% for 6 months. The stability of lozenges tablets was evaluated by studying the physicochemical parameters such as weight uniformity, diameter, thickness, hardness, friability, and dissolution at different time intervals of 0, 1, 2, 3, and 6 months.

Statistical methods The statistical significance of the result was determined by analysis of variance 20 (ANOVA) using a one way and a two-way ANOVA in Excel. P-values less than 0.05 were considered as statistically significant (p<0.05).

Results of experiments In the present disclosure, SD is standard deviation.

Physical properties of the oral lozenges Direct compression as a tabletting method does not require heat and solvents and 30 therefore any potential issues surrounding heat and solvent drug/excipient can be easily overcome.

The first step was to evaluate the impact of different compression forces on lozenge properties to ensure sufficient mechanical integrity and low friability.

The physical properties of the lozenge tablet formulations are presented in Table 2.

Table 2: Physical properties of lozenges tablets at different compression forces. Each s point represents mean ± SD (n=3) Compression force (tonnes) 2 4 6 8 Weight (mg) 499.97 ±0.04 499.99 ±0.02 500.00 ±0.01 500.00±0.09 Hardness (kp) 9.97 ±0.04 11.92±0.01 12.25 ±0.07 13.93 ±0.03 Friability (%) 1.00 ±0.02 0.60 ±0.01 0.30 ±0.09 0.20 ±0.04 Diameter (mm) 10.00 ±0.09 10.00 ±0.03 10.00 ±0.01 10.00 ±0.02 Thickness (mm) 4.55 ±0.02 4.32 ±0.07 4.30 ±0.01 4.30 ±0.08 All the lozenge tablets showed higher hardness and strengths with the increase in compression force. This could be due to the higher force, from 4 to 8 tonnes, used to compress the lozenge formulations. Blending time and lubricating of the tablets also contributed to the high strength. All formulated lozenges at four different compression forces showed acceptable levels of friability of less than 1%. Moreover, the resultant tablets showed acceptable weight variation in the range 499.97-500.0mg. Therefore, all the lozenge tablets exhibited acceptable physical characteristics.

Effect of Compression Force on Hardness Hardness is a measurement of tablet strength. It provides insight into the force required to break a tablet and its ability to withstand breakage, crumbling or chipping under the conditions of storage, transportation, and handling. Generally, hardness is dependent on type and concentration of binder, tablet diameter and compression force. There was a significant effect on the hardness of the tablet with four different compression forces as presented in Table 2. ANOVA analysis revealed a significant difference in tablet hardness with an increase in compression pressure (p<0.005). This could be due to gas displacement from the powder bed in the die as compression pressure increases when bringing particles in close contact. This therefore causes an increase in the number of particles in contact with the material thereby increasing particle-particle interaction leading to formation of a strong bond which increases the mechanical strength of the tablet at high compression pressure.

Effect of Compression Force on Friability The friability test for tablets is used to assess the ability of the tablets to withstand shock and abrasion encountered during packaging, transportation, and handling. The friability values decreased as compression pressure increased for all the formulations as presented in Table 2. There is a decrease in friability with the increase in compression force. This could have been due to the formation of more solid bonds which led to the formation of tablets with increasing hardness and more resistance to fracture and abrasion.

Characterization of Tablet Erosion The lozenge tablets were placed in a 6-well plate with water as a medium for evaluating erosion/swelling over 45 minutes. The observation was timed from 0 minutes until there was no change in thickness and diameter of lozenges tablets.

Figure 1 depicts an evaluation of the thickness of the lozenges at different compression forces. Each point represents mean ± SD (n=3) p<0.05. Figure 1 shows that the thickness of the lozenges increased with time.

Figure 2 depicts an evaluation of the diameter of lozenges at different compression 25 forces. Each point represents mean ± SD (n=3) p<0.05. Figure 2 shows that the diameter of the lozenge tablets also increased with time.

Drug Release Study by Dissolution Figure 3 depicts the drug release of lozenges made at four different compression forces. Each point represents mean ± SD (n=3) p<0.05. As the compression force increases, the powder becomes densely packed together with no inter-particulate void spaces for any relative particle movement. At this stage, stress starts to build-up at the particle contact point in the die and the material begins to deform. The particles would have deformed above the elastic limit of the material. But if the force is not strong enough for it to exceed the elastic limit of the particle, the tablet would be unstable and crumble. Once compression is below the limit, materials will not form a coherent tablet while compression above this limit, materials form a coherent tablet with increasing strength as the compression force increases.

In this study, it was observed that increases in compression force at four different compression forces showed a significant difference in the percentage of drug release rate.

At two tonne, drug release was 108%, four tonne was 92%, six tonne was 69% and eight tonne was 64% in the first 20 minutes. Drug released from matrix tablets takes place because of hydration with the dissolution medium. The hydrated portion leads to the formation of channels for drug to diffuse out. It causes the rate determining step in matrix tablet dissolution. While disintegration is not desirable in a matrix tablet, dissolution occurs from the dosage form.

There was a significant effect of compression pressure on the mechanical properties of the matrix tablets. However, the release properties of CHX lozenges tablet formulations were significantly influenced with increase in compression pressure. It can therefore be concluded that the matrix forming polymer and the material properties of the drug together with the compression pressure influenced drug release profiles.

An oral lozenge according to the disclosure remains intact and gradually disintegrates to release its content, without drug dumping.

Stability Studies The aim of stability studies is to provide evidence on how the performance of the formulation containing the API changes over time as a result of a variety of environmental factors. Moreover, this study was used to evaluate drug release from the matrix lozenges tablets in vitro. Stability studies were carried out on lozenges compressed at 4 tonnes. During this stability study, lozenges tablets were characterized for physicochemical analysis such as hardness, friability, weight uniformity, and drug release.

Table 3: Evaluation of Stability Studies of Chlorhexidine Lozenge Tablets Time (day) Hardness Friability (%) Weigh Drug content (Kp) uniformity (%) (mg) 1 11.5±0.13 0.07±0.06 500.00±0.34 98.41 ±0.04 11.4±0.15 0.08±0.12 500.00±0.40 96.62 ±0.10 10.9±0.04 0.09±0.24 500.00±0.46 95.62 ±0.07 10.6±0.08 0.11±0.03 500.00±0.57 92.43 ±0.06 10.6±0.25 0.12±0.17 500.00±0.58 90.13 ±0.05 The results in Table 3 indicate no significant changes in the physical properties of the lozenges during 6 months (180 days) of stability studies. Similarly, drug release data remain unchanged throughout the stability period, as shown in Figure 4. Figure 4 depicts an evaluation of drug release of CHX lozenges according to stability study for 1, 30, 60, 90 and 180 days. Each point represents mean ± SD (n=3) p<0.05 Each sample of lozenge tablets from long term stability periods (from 1 to 180 days) was analysed using in vitro dissolution study to measure drug released within 20 minutes.

During the stability analysis, there were no adverse changes in the appearance and performance of the tablet over a period of six months Results from this investigation has shown that chlorhexidine-based lozenges can be 20 prepared using direct compression method and that the impact of storage conditions is minimal on the integrity and stability of the dosage form.

Evaluation of a heat free method of tabletting, direct compression enabled the formulation of lozenges with different release profile. Compression force can be used to alter drug release profile without changing the composition of the formulation. This is a significant advantage for the formulator whereby alteration of manufacturing conditions without changing the composition allows control of physical properties and drug release profiles.

s Effect of xylitol on biofilm formation by Streptococcus mutans As indicated above, in some examples an oral lozenge according to the disclosure has a weight of 500 mg. In examples of the disclosure, oral lozenges comprise from 0.005 to 4% w/w chlorhexidine or a salt thereof. In the example shown in Table 1 above, the oral lozenge comprises 4% w/w (20 mg) chlorhexidine. In other examples, the oral lozenge may comprise, for example, 0.005% w/w (0.025 mg) chlorhexidine or a salt thereof, or 0.05% w/w (0.25 mg) chlorhexidine or a salt thereof. Accordingly, an oral lozenge weighing about 500 mg may comprise from 0.025 mg to 20 mg chlorhexidine or a salt thereof.

In the example illustrated in Table 1, the oral lozenge comprises 65.5% w/w (327.5 mg) xylitol. In other examples, the oral lozenge may comprise, for example 2% w/w (10 mg) xylitol, or 80% w/w (400 mg) xylitol. Accordingly, an oral lozenge weighing about 500 mg may comprise from 10 mg to 400 mg of xylitol. In other examples, oral lozenges may instead comprise from 2% w/w to 80% w/w sorbitol, erythritol or maltitol.

Oral lozenges according to examples of the disclosure are capable of delivering an MIC and/or MLC of chlorhexidine (or a salt thereof) to inhibit oral biofilm formation and are thus capable of preventing or treating gingivitis and/or preventing or treating dental caries. This is based on a dissolution and absorption time of about 15 to 30 minutes upon administration to the oral cavity. The patient controls the rate of dissolution and absorption by sucking the oral lozenge until it dissolves.

As described below, it has been found that the MIC and/or MLC of chlorhexidine (or a salt thereof) is from 0.00001 to 0.0004 % w/v (0.1 to 4.0pg/m1) when provided in combination with from 2 to 40% w/v xylitol, sorbitol, erythritol or maltitol. In some examples, it has been found that the MIC and/or MLC of chlorhexidine (or a salt thereof) is 0.5 pg/ml) when provided in combination with from 2 to 5% w/v xylitol (0.02- 0.05 g/ml). Accordingly, there is a synergistic interaction between chlorhexidine (or a salt thereof) and the selected polyol at these concentrations.

It has surprisingly been found that xylitol, sorbitol, erythritol and maltitol act synergistically with chlorhexidine (or a salt thereof) to enhance the effectiveness of chlorhexidine (or a salt thereof) for use in inhibiting oral biofilm formation based on improved antibacterial effectiveness against Streptococcus mutans, thus preventing or treating gingivitis and/or preventing or treating dental caries.

Because of the synergistic effect, the dosage of chlorhexidine (or a salt thereof) delivered by oral lozenges of the disclosure is more potent at lower concentrations of chlorhexidine (or a salt thereof) than dosages delivered by known oral lozenges. Accordingly, the amount of chlorhexidine (or a salt thereof) present in oral lozenges according to the disclosure is reduced compared to known oral lozenges. This improves performance and reduces teeth staining Furthermore, this could lead to addressing the problem of antimicrobial resistance.

The MIC is defined as the lowest concentration of an antimicrobial agent that completely inhibits bacterial growth and is determined by the highest dilution at which no visible growth is observed. MLC is defined as the lowest concentration of an antimicrobial agent that kills 99.9% of the initial inoculum in 24 hours using a plate count of viable cells at 37°C.

Evidence of synergistic effect Time Kill Studies Bactericidal activity is defined as greater than 3 log10 fold decrease in colony forming units (surviving bacteria), which is equivalent to 99.9% killing of the inoculum according to guideline M26 Method (Clinical Laboratory Standard Institute, 1999).

Synergism between xylitol and CHX was shown by a time-kill test. Xylitol alone was found to decrease bacterial viability when the incubation time was increased as compared to control with an initial inoculum of 107 CFU/mL. The effect of CHX on Streptococcus mutans viable cell count with time was studied as depicted in Figure 5. Figure 5 depicts a time kill curve of Streptococcus mutans exposed to CHX (10pg/m1), Xylitol (40% w/v), and Xylitol (40% w/v)-CHX (10 pg/ml). Log CFU indicated for absorbance reading for duration time for 24 hours. Values represent, Mean (n=3), ±SD and (p<0.05).

The results show that at the MLC, cell viability was decreased within the first 60 minutes and eventually by 2 log, for both the MLC CHX and xylitol, and the positive control showed no change in cell viability over the tested period. However, 40% Xylitol-to CHX combination showed a further decrease from initial incubation times and a further decrease in CFU/mL compared with Xylitol after 24 hours of incubation. Incubation time is chosen for 24 hours due to Streptococcus mutans growth in the planktonic form. Log reduction in CFU/mL of the combination 40% Xylitol-CHX show decreased by more than 3 10g10 when compared to xylitol alone. Furthermore, log reduction in CFU/mL of the combination 40% Xylitol-CHX show decreased by 2-log10 when compared to CHX alone.

Effect of xylitol on biofilm formation in combination with CHX Figure 6 depicts biofilm formation of Streptococcus mutans at 72 hours at a xylitol concentration of 2, 5, 10, 20 and 40% and a CHX concentration of 0.1, 0.5, 1, 2 and 4 pg/ml, OD 600nm, mean ±SD, n=3.

As shown in Figure 6, even at low concentrations (0.1pg/m1) of the antimicrobial agent CHX, xylitol has an inhibitory impact on biofilm formation.

Increasing concentration of xylitol from 2 to 40%, resulted in gradually decreased biofilm density at 0.1pg/m1 of CHX. Moreover, between 2% and 40% of xylitol there was 85% decreased in biofilm density at 0.1pg/m1 of CHX. However, when comparing 0.5 pg/ml concentration of CHX with presence of 10% xylitol, the biofilm inhibition showed a significant difference (p<0.014). The data demonstrate that the combination of xylitol and low concentrations of CHX has synergy and results in effective inhibition of Streptococcus mutans biofilm.

Reduction in cell viability in biofilms Cell vitality is a crucial factor in the establishment and survival of biofilms. This study helped estimate cell vitality during biofilm formation. Table 4 shows vitality of Streptococcus mutans biofilms as a percentage at various combinations of xylitol with CHX. The samples were taken after biofilm formation by Streptococcus mutans in the presence of CHX at a concentration of 0.1, 0.5,1.0, 2.0 and 4.0 pg/m I and 2, and 5 % xylitol. Mean, (n=3), ±SD. The equation used was as follows: [vital, (S9, green) bacterial] Percentage of vitality = . x 100% (59, green) + dead (PI, red) bacterial]

Table 4

Samples of Biofilm Formation Green CellRed Cell Vitality % count count S. mutans 70124 41633 63 S. mutans with 0.1pg/m1 CHX 5752 5056 53 S. mutans with 0.5pg/mICHX 6347 10246 38 S. mutans with 1.0pg/mICHX 10037 18410 35 S. mutans with 2.0pg/mICHX 2983 6427 32 S. mutans with 4.0pg/mICHX 10783 29128 27 S. mutans +2% Xylitol 9863 10109 49 S. mutans + 2% Xylitol + 0.5 pg/ml CHX 10711 12594 46 S. mutans + 5% Xylitol 6798 36743 16 S. mutans + 5% Xylitol 0.1 pg/ml CHX 7598 52347 13 In Table 4 above, S. mutans is Streptococcus mutans. The findings of the present study indicated that Streptococcus mutans control biofilm formation showed the highest percentages of vital cells, 63%. However, with increase in concentration of CHX, the vitality of cells in biofilm decreases. When 2% xylitol was added to Streptococcus mutans control, there is also 14% decrease of vitality. Moreover, 2% xylitol was added with 0.5 pg/ml of CHX, the vitality was further decreased by 3% compared to control. Following increases of percentage of xylitol 5% in biofilm of Streptococcus mutans, there was a big decrease in vitality of from 63% to 16% between both control and treated. However, when 5% xylitol biofilm was combined with CHX concentration at 1.0 pg/ml, the vitality showed a decrease to 13%. This showed that a huge decrease in percentages of vitality of Streptococcus mutans s biofilm with increased of CHX concentration.

Accordingly, synergism was observed when CHX combined with different concentrations of xylitol was tested on the biofilm formation of Streptococcus mutans. The inhibition was greater when the antimicrobial agent, CHX and xylitol were used in combination rather than CHX alone.

The study revealed that the biofilm formation of pathogenic bacteria, Streptococcus mutans could be efficiently killed by corresponding treatment with low concentration of xylitol and CHX.

This strategy for the control of pathogenic biofilms has proved a synergistic effect between xylitol and CHX. The interaction between xylitol and CHX showed a significant effect in the inhibition of biofilms, as they disrupted the biofilm as well as having bactericidal effect on cells by effecting their vitality.

Reduction in biofilm matrix Extracellular polysaccharides (EPS) production is a crucial factor in the establishment and survival of biofilms.

The percentage of EPS produced in the presence of xylitol 2%, 5% and 10% and concentration of CHX at 0.5 pg/ml and 1.0 pg/ml was calculated by the formula: [EPS -related fluorescent (Con A red)] % EPS Production - x 100 [bacteria (S9, green) + EPS -related fluorescent (Con A, red)] and is depicted in Figure 7. Figure 7 depicts percentage EPS production in Streptococcus mutans biofilms during inhibition assay at 72 hours with (2%, 5% and 10%) of xylitol treated with 0.5 and 1.0 pg/m I CHX concentration, n=3 ±SD.

Control Streptococcus mutans show the highest production of EPS (64.36%) compared to other samples. However, when 2% of xylitol was added into the biofilm medium, EPS production decreases compared to the control by 7.7%. Moreover, when 0.5 and 1.0 pg/ml of CHX added into each well during development of biofilm of Streptococcus mutans, the production of EPS showed a decrease to 44% for 2% xylitol combined with CHX 0.5 pg/ml and 37.69% for 2% xylitol combined with CHX 1.0 pg/ml.

However, the biofilm formation of Streptococcus mutans with 5% xylitol showed 45.96% EPS production. When this biofilm combined with 0.5 pg/ml of CHX, the development of EPS decreases to 19.10% which was almost 3 times reduced when compared to control Streptococcus mutans biofilm formation. While this biofilm formation of Streptococcus mutans exposure to 5% xylitol combined with 1.0 pg/ml of CHX, the production of EPS was reduced to 11.80%. Both samples showed slightly reduced EPS production with increase in concentration of CHX from 0.5 to 1.0 pg/ml.

The exposure of Streptococcus mutans biofilm formation to 10% xylitol, the production of EPS was 45.48%. There was a reduction of EPS production compared to Streptococcus mutans control. However, when 10% xylitol combined with 0.5 pg/ml, the EPS production was show reduce 18.37% meanwhile with 1.0 pg/ml it was 11.26%. Both concentrations indicated reduction of EPS with increase in concentration of CHX.

Overall EPS production of Streptococcus mutans during biofilm formation grown in Brain Heart Infusion (BHI) medium containing increasing concentrations of xylitol and 30 CHX showed tremendous decrease.

Effect of sorbitol on biofilm formation in combination with CHX Figure 8 depicts biofilm formation of Streptococcus mutans at 72 hours at a sorbitol concentration of 2, 5, 10, 20 and 40% and a CHX concentration of 0.1, 0.5, 1, 2 and 4 pg/ml, OD 600nm, mean ±SD, n=3.

It is evident from Figure 8 that the presence of sorbitol in addition to CHX decreases the density of the biofilm at a low concentration of 0.5pg/m1 of CHX compared to Streptococcus mutans control. Sorbitol at concentration 2 to 40% combined with 2pgiml CHX had a complete inhibitory effect on biofilm formation. In addition, inhibition with 40% sorbitol and CHX at 2pgiml was similar to inhibition of biofilm with 4 pg/ml of CHX. There showed a significance different between both concentrations, (p<0.05).

Accordingly, sorbitol also has synergistic inhibitory effects with chlorhexidine on biofilm formation by Streptococcus mutans, for instance at lower concentrations of chlorhexidine. Erythritol and maltitol also have a synergistic inhibitory effect with chlorhexidine on biofilm formation by Streptococcus mutans, for instance at lower concentrations of chlorhexidine.

Examples of the disclosure also provide a method of preparing an oral lozenge according to any of the preceding claims, the method comprises blending a mixture comprising 0.005 to 4% w/w chlorhexidine or a salt thereof and 2 to 80% w/w xylitol, sorbitol, erythritol or maltitol. The method further comprises compressing the blend into an oral lozenge.

The excipients in the blend are weighed before blending. In some examples, the blend is lubricated. Accordingly, in some examples the method comprises in sequence: weighing, blending, lubrication, and compression.

The method may comprise applying a compression force on the blend of from 2 to 8 tonnes. In some examples, the method comprises applying a compression force on 30 the blend of 4 tonnes.

There is thus described an oral lozenge and a method of preparing an oral lozenge with a number of advantages as described above.

Although embodiments of the present invention have been described in the preceding paragraphs with reference to various examples, it should be appreciated that modifications to the examples given can be made without departing from the scope of the invention as claimed.

Features described in the preceding description may be used in combinations other than the combinations explicitly described.

Although functions have been described with reference to certain features, those 10 functions may be performable by other features whether described or not.

Although features have been described with reference to certain embodiments, those features may also be present in other embodiments whether described or not.

Whilst endeavouring in the foregoing specification to draw attention to those features of the invention believed to be of particular importance it should be understood that the Applicant claims protection in respect of any patentable feature or combination of features hereinbefore referred to and/or depicted in the figures whether or not particular emphasis has been placed thereon.

Unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like, are to be construed in an inclusive as opposed to an exclusive or exhaustive sense; that is to say, in the sense of "including, but not limited to".

Claims

CLAIMS1. An oral lozenge, the oral lozenge comprising: 0.005 to 4% w/w chlorhexidine or a salt thereof; and 2 to 80% w/w polyol, wherein the polyol comprises xylitol, sorbitol, erythritol or maltitol.
2. An oral lozenge according to claim 1, wherein the polyol is xylitol.
3. An oral lozenge according to claim 1 or 2, wherein the oral lozenge comprises: 0.05 to 4% w/w chlorhexidine or a salt thereof.
4. An oral lozenge according to claim 1 or 2, wherein the oral lozenge comprises: 0.05 to 2% w/w chlorhexidine or a salt thereof.
5. An oral lozenge according to claim 1 or 2, wherein the oral lozenge comprises: 0.05 to 1% w/w chlorhexidine or a salt thereof.
6. An oral lozenge according to claim 1 or 2, wherein the oral lozenge comprises: 0.005 to 0.1% w/w chlorhexidine or a salt thereof.
7. An oral lozenge according to any of the preceding claims, wherein the oral lozenge comprises: 2 to 40% w/w polyol.
8. An oral lozenge according to any of claims 1 to 6, wherein the oral lozenge comprises: 2 to 15% w/w polyol.
9. An oral lozenge according to any of claims 1 to 6, wherein the oral lozenge comprises: to 80% w/w polyol.
10. An oral lozenge according to any of the preceding claims, wherein the oral lozenge comprises chlorhexidine in the form of a salt which is chlorhexidine diacetate.
11. An oral lozenge according to any of the preceding claims, wherein the oral lozenge S has a hardness of from 9 to 14 kp.
12. An oral lozenge according to any of the preceding claims, wherein the oral lozenge has a friability of from 0.07 to 1.5 %.
13. An oral lozenge according to any of the preceding claims for use in inhibiting oral biofilm formation, treating or preventing gingivitis, and/or treating or preventing dental caries.
14. A method of preparing an oral lozenge according to any of the preceding claims, the method comprising: blending a mixture comprising from 0.005 to 4% w/w chlorhexidine or a salt thereof and from 2 to 80% w/w polyol, wherein the polyol comprises xylitol, sorbitol, erythritol or maltitol; and compressing the blend into an oral lozenge.
15. A method according to claim 14, wherein the method comprises: applying a compression force on the blend of 4 tonnes.