Patent Application
20240009139
The present invention relates to a stable gel for use in topical treatment of wounds and surface areas of the body. More specifically the invention provides a stable, cavity filling gel formulation with low bioadhesive strength and cohesive integrity which carries at least one pharmaceutical or cosmetically active ingredient.
The invention primarily addresses the area of PVA gels subjected to reversible or partially reversible cross-linking, for use in wound care to deliver one or more substances topically. The substances can be antibiotics or other drugs or anaesthetics or antiseptics.
PVA-Borate hydrogels display unique flow properties that allow for their use in wound treatment. These gels will flow under low shear to fill the wound cavity and can be removed as a solid mass post treatment due to their shear thickening properties. As described in EP 2203192, formulating PVA-borate hydrogels with drug substances, such as lidocaine hydrochloride, allows for an ideal platform to deliver drugs to the wound cavity.
It has, however, been found that the PVA-borate hydrogels described above are prone to instability. In particular, the viscosity and the appearance of known PVA-borate hydrogels changes detrimentally on storage. That is, the viscosity decreases and the system can separate into two phases making it unachievable to remove the gel from a wound in one intact unit. Furthermore, the appearance changes such that the gels go from clear to opaque. This instability can render the gels unsuitable for the treatment of wounds because a sufficient shelf life of equal to or greater than two years cannot be achieved.
The present invention is based upon making a semisolid gel delivery system which is mouldable when handled, acts like a viscous liquid when placed in a space where it has room to flow, which is stable for at least two years on storage and which may be sterilised.
Wound infection may be defined as the entry, growth, metabolic activity and resulting pathophysiological effects of a microorganism upon patient tissue. Wound preparations should ideally be sterilised. Infection has been shown to impair wound healing for both acute and chronic wounds. The increasing resistance of wound infections to both systemic and topical antibiotics has made effective treatment more difficult and accordingly, there is interest in the development of new treatment regimens.
It is an aim of the present invention to provide a PVA-borate gel system incorporating an active ingredient such as a local anaesthetic, for example lidocaine hydrochloride, or antibiotics or photosensitising compounds that form part of PACT and are able to photosensitise bacterial cells or other pathogens making them amenable to the photodynamic effect, wherein the gel system has flow properties suitable for filling a wound, is stable at ambient temperature and pressure for at least two years and may be sterilised.
Surprisingly, it has been found that the aforementioned instability can be overcome by forming PVA-Borate hydrogels which contain less than 5% acetic acid using a PVA grade with a molecular weight between 100,000 and 300,000 Daltons and a degree of hydrolysis of between 98 and 100%.
According to a first aspect of the present invention there is provided a sterile gel formulation suitable for topical use and in filling a wound cavity and delivering an active ingredient thereto, the gel further having a pH range of 4.5 to 8.5, preferably a pH range of 6.5 to 7.5, having low bioadhesive strength and cohesive integrity and being formed from a polymer selected from among the group consisting of poly(vinyl) alcohol (PVA) polymer and a PVA-polyvinyl acetate copolymer, a cross-linker able to form associative interactions between and within said polymer, preferably but not limited to a salt form of boron that produces borate ions in aqueous solution such as borax, at least one compound which has a beneficial effect as an active ingredient in the wound and at least one modulator, the modulator being a low molecular weight species that is capable of binding borate or PVA in aqueous solution through a mono-diol or di-diol formation and can reduce the pH of PVA-borate hydrogels, wherein the polymer has a degree of hydrolysis of between 98 and 100% and a molecular weight of from 100,000 to 300,000 Daltons and wherein the gel is heat and/or gamma sterilised and contains less than 5% acetic acid.
Such gels retain their clear appearance and viscosity and retain their stability for more than two years.
Preferably, the modulator is a low molecular weight compound possessing a plurality of hydroxyl groups able to bind to borate and the compound being preferably a sugar alcohol and most preferably the modulator being D-mannitol.
D-mannitol belongs to a group of chemicals described as sugar alcohols. Other sugar alcohols, whilst may not being as affective as D-mannitol, can also be used to produce the same effect as D-mannitol. Additionally, other low-molecular weight molecules containing two hydroxyl groups on neighbouring carbon atoms, in the cis-position, can also be used to bind borate and reduce the pH of PVA-borate hydrogels. Other sugar alcohols and compounds possessing the characteristics and structural features of two hydroxyl groups, in the cis-position and attached to adjacent or neighbouring carbon atoms so as to allow presentation of two or more hydroxyl functionalities in a conformation recognisable as a cis conformation, which may be used in a gel formulation of the present invention include but is not necessarily limited to maltitol, dulcitol, D-sorbitol, xylitol and meso-erythritol.
Whilst PVA is the best candidate polymer, other polymers with extensive hydroxyl functionalities could also be used, for example a copolymer of PVA and polyvinyl acetate.
Advantageously, the amount of polymer in the gel formulation ranges from 8 to 20% w/w, preferably 10 to 20% w/w, particularly preferably from 11 to 15% w/w, e.g. 12% w/w.
The molecular weight of the polymer used in practice of the invention is from 100,000 to 300,000 Daltons, preferably from 145,000 to 200,000 Daltons, for example 150,000 Daltons, particularly preferably 145,000 Daltons.
The polymer used in practice of the invention has a degree of hydrolysis of between 98 and 100%, preferably 99%.
The amount of borate used in preparing the gel depends on the type of polymer, e.g. PVA, used. Typically from 0.5 to 5% w/w borate could be used. More typically 1.5 to 4% w/w and most preferably from 1.5 to 3% w/w, e.g. 2.5% w/w. In a particularly preferred embodiment, the amount of borate used in preparing the gel is 1.8% w/w.
The amount of modulator added in the preparation of the gel depends on the polymer, e.g. PVA, and borate and the choice of modulator. Typically from 0.1 to 5% w/w could be used. More preferably from 0.5 to 2% w/w. For example, mannitol is a better modulator than glycerol and therefore less mannitol would be required than glycerol. In a particularly preferred embodiment, the gel contains 2.0% w/w D-mannitol.
Gels prepared according to the invention contain less than 5% acetic acid, for example between 2 and 4% w/w, preferably less than 2% w/w, particularly preferably less than 1% w/w acetic acid. Ideally, the gels are substantially free from acetic acid.
The gel of the invention can be mounted on or incorporate a support such as a mesh or gauze. This may be advantageous to cover a large surface area. Preferably, the support is provided with adhesive, e.g. an adhesive border, for attachment to a patient's skin.
Upon application to intact skin, the gel according to the invention will flow and take on a convex shape. A thin, wedge-shaped peripheral edge is formed that begins to dry from the edge inwards. Once dry, the gel is wrinkled and rough and no longer adheres to the skin.
In a preferred embodiment, the sterile gel formulation is used in combination with a porous support such as paper, mesh or gauze to form a patch. Placing the porous support onto the gel after application of the gel to a surface prevents the radial drying effect described above. The porous support changes the drying profile such that the gel dries downwards perpendicularly to the surface. The porosity of the outer support can be adjusted to modify the drying profile as desired.
Without being bound by theory, it is suggested that when the patch-like gel with porous support is applied to skin, it flows to make intimate contact with the skin and immediately begins to hydrate it. This opens aqueous skin channels allowing the active ingredient in the gel to permeate the skin. Due to the porosity of the outer support, water slowly evaporates from the outer surface. As a result, the height of the patch slowly decreases and the volume of the patch reduces accordingly. It is reasonable to assume that this increases the amount of active ingredient per unit volume. Therefore, over time, the patch self-compensates for the loss of active ingredient into the skin and automatically adjusts the concentration gradient upwards, thus maintaining the driving force of active ingredient into the skin.
In one preferred embodiment the active ingredient is lidocaine, preferably a salt form of lidocaine, most preferably lidocaine hydrochloride monohydrate. Alternatively, the active ingredient can be another amide local anaesthetic such as prilocaine, bupivacaine etc. or indeed any active ingredient that produces a conjugate acid and is stable in the presence of borate ions.
The amount of active ingredient added in the preparation of the gel depends on the choice of active agent. Typically from 0.1 to 10% w/w could be used. More preferably from 0.5 to 5% w/w, e.g. 4% w/w.
The gel formulations described herein are intended of for use in the topical treatment of wounds, in particular for use in wound protection, sealing a wound, preventing blood loss from a wound, the prevention of wound infection and/or the removal of debris from a wound. Examples of debris that may be removed from a wound using the gel formulations described herein are grit, dust, glass and loose tissue.
Accordingly, in a further aspect the present invention provides for gel formulations for use in wound protection, sealing a wound, preventing blood loss from a wound, the prevention of wound infection and/or the removal of debris from a wound.
The gel formulations described herein are also intended for use in topical treatment of intact surface areas of the body, in particular for use in the treatment of pain and/or injuries. For example, the gel formulations described herein may be used in the topical treatment of one or more conditions selected from among contusions, Morton's neuroma, sunburn, general neuralgias, soft tissue injuries, e.g. to fingers and toes, sprains, e.g. sprained ankles and wrists, rheumatoid joints, e.g. rheumatoid finer and toe joints, gout, e.g. gout in toes, post herpetic pain, scars, e.g. painful scars, back pain, broken bones, e.g. broken toes, fingers or ribs, scalds, minor burns, nettle stings, insect bites, vasculitis, chilblains, cold sores, corns, bunions and tendonitis, e.g. tendonitis in ankle, elbow, wrist, knee or shoulder.
In a further aspect, the invention provides a process for preparing the sterilised gel formulation of the invention, comprising:
In a preferred embodiment, heat sterilisation is carried out at a temperature of from 121° C. to 131° C., particularly preferably for a duration of from 5 to 20 minutes, e.g. 121° C. for 15 minutes.
In yet a further aspect, the invention provides a method of treatment of a wound, said method comprising at least the following steps:
Generally, the gel formulation will be an intact mass upon removal.
The gel formulation resides within the wound cavity for a predetermined period of time to allow absorption of the active ingredient such that the active ingredient may exert a clinical effect. This predetermined period of time prior to removal will vary depending on the active ingredient and is preferably in the range of from about 1 minute to about 48 hours, particularly preferably from about 10 minutes to about 6 hours, e.g. about 1 hour to about 4 hours. However, this is not considered to be limiting and other time periods are within the scope of the invention.
In a further aspect, the invention provides a method of treatment of pain in a human or animal patient, said method comprising at least the following steps:
The gel formulation is left on the skin surface for a predetermined period of time to allow absorption of the active ingredient such that the active ingredient may exert a clinical effect. This predetermined period of time prior to removal will vary depending on the active ingredient and is preferably in the range of from about 1 minute to about 48 hours, particularly preferably from about 10 minutes to about 6 hours, e.g. about 1 hour to about 4 hours. However, this is not considered to be limiting and other time periods are within the scope of the invention.
In a preferred embodiment of the method of treatment of pain, the support attaches securely to the exposed surface of the applied gel formulation. In this embodiment, the support restricts the movement and drying of the underlying gel formulation. For example, the support may be a fibrous cover for attachment to the gel formulation surface.
In an alternative preferred embodiment, the support is provided with adhesive for attachment to surrounding skin to restrict movement and drying of the underlying gel formulation.
The invention will hereinafter be more particularly described with reference to the following Figures, which show by way of example only, particular embodiments of the gel according to the invention.
In the drawings:
The following description outlines that low degree of hydrolysis PVA blank hydrogels exhibit turbidity, phase separation and an acetic acid-like odour on storage. These unwanted changes cannot reversed by simple heating and mixing. Higher degree of hydrolysis (99%) PVA blank hydrogels according to the invention do not exhibit such changes.
For lidocaine HCl loaded PVA-THB hydrogels, hydrogels prepared with polymers having 99% hydrolysis are superior to lower degree of hydrolysis PVA hydrogels in almost all physicochemical properties and lidocaine HCl is generally stable in the higher degree of hydrolysis formulation at 20° C.
The effect of degree of hydrolysis on the stability of both drug loaded and placebo/blank hydrogels is unexpected. This knowledge can be used to successfully manufacture stable PVA-THB hydrogels.
Measurement of stability parameters was conducted for both Lidocaine loaded and blank (placebo) hydrogels.
Preparation
PVA and borax were obtained from Merck® (Merck Millipore Catalogue Nos. 141350-354, 141356 and 106303, respectively). PVA stock solution and 5% borax solution were prepared in advance of preparing the hydrogels.
20% PVA stock solution sufficient to result in a final PVA concentration of 10% w/w was weighed into an empty container followed by gradual addition with stirring of 5% borax solution sufficient to result in a final borax concentration of 2.5% w/w. The resultant gel was kept in a water-bath at 85° C. for 30 minutes. After heating, the gel was stirred thoroughly to make it as homogenous as possible and poured into containers. The compositions of fresh and 9 month old blank PVA-THB hydrogels are displayed in Table 1 below.
The viscosity of the PVA in standard solution as listed under PVA type in Table 1 above (e.g. 4 mPAs, 5 mPAs, 28 mPas) is proportional to the molecular weight of the PVA chains. For example, the molecular weight of 28-99 PVA is about 145,000 Daltons.
All 9 month old blank hydrogels prepared with lower degree of hydrolysis (PVA (4-88, 5-88, 8-88, 26-88 and 40-88)) and higher degree of hydrolysis (PVA (28-99)) were observed for colour or phase changes.
pH and Rheological Measurement
The pH, storage (G′), loss (G″) moduli and loss tangent of fresh and 9 month old blank PVA-THB hydrogels (Table 1) were determined. Measurements were carried out using a controlled stress rheometer (AR 1500, TA Instruments, New Castle, DE, USA) with Rheology Advantage Data Analysis Program Version 5.7.0, TA. Parallel plate geometry (20 mm, 1 mm gap) was used for the prepared hydrogels. The experimental temperature was efficiently monitored at 25° C. (±0.1° C.). The rheometer instrument was programmed for set temperature (25° C.) and equilibration for 3 min. Stress sweep (0.1 to 100 Pa) was performed on all samples at three different frequencies (0.1, 1, 10 Hz) to check the linearity of stress vs. strain curve within the range studies. Frequency sweep from 0.1 to 100 Hz at constant stress of 60 Pa was also performed on each samples to find out storage (G′) and loss (G″) moduli.
Re-Heating Experiments and Effect of Heating Time
Some of the 9 month old hydrogels showed a turbid/opaque appearance and even de-mixing (phase separation). To check the reversibility of such changes, these 9 month old hydrogels were again heated at 85° C. for 30 minutes. Various physicochemical parameters such as storage (G′), loss (G″) moduli as well as hardness and compressibility were determined for the re-heated 9 month old hydrogels.
To investigate a previously observed phase change on extended heating for 88% hydrolysed PVA, 26-88 and 28-99 hydrogels were freshly prepared with different periods of heating at 85° C. (1, 2 and 3 hours). The physical form (homogenous or de-mixed) was observed after cooling to room temperature.
Results
Visual Observation
All 9 month old blank hydrogels prepared were observed for physical appearance and phase separation. The representative photographs of PVA blank hydrogels listed in Table 1 (batch numbers 1-6) are shown in
As can be seen in Table 2 and
The turbidity was proportional to the molecular weight of PVA chains. 4-88, 5-88 and 8-88 hydrogels did not show phase separation but 26-88 and 40-88 hydrogels showed de-mixed phases. De-mixing was more significant with 40-88 hydrogels than with 26-88 hydrogels.
The major difference between the gels which displayed some sort of time dependent change and those which did not is the degree of hydrolysis. This suggests that the observations are attributable to the difference in the number of residual acetate groups present on the PVA chains.
Without being bound by theory, it is suggested that hydrolysis of residual acetate groups leads to the liberation of residual acetic acid groups which causes a reduction in the local pH which discourages the diol-THB interaction and encourages degradation of PVA chains. Furthermore, the resultant degraded PVA chains and disrupted interaction between the diol-groups and THB anions are thought to encourage hydrophobic interactions between non-polar regions of the polymer which could possibly be sufficient to cause the turbidity seen.
pH
The pH of fresh and 9 month old hydrogels are displayed in
Rheological Measurement
Stress sweep and frequency sweep were performed on blank PVA hydrogels. The main objective of stress sweep was to check the linearity of strain vs. stress curves at different frequencies (0.1 to 10 Hz used during frequency sweep). By checking the linearity over the studied frequencies it can be ascertained that the frequency measurement is carried out within the elastic limit.
The results of the stress sweep over a range of 0.1 to 100 Pa at three different frequencies (0.1, 1, 10 Hz) are graphically represented in
For gels made with a lower degree of hydrolysis PVA, as the molecular weight (and hence the viscosity) of the PVA increased, the loss of strain after storage for 9 month tended to decrease. The loss of strain after 9 month storage was greatest for 4-88 and least for 40-88 PVA hydrogel. However, the hydrogels were still elastic (linear over the range of stress and frequency studied) after 9 month storage at 20° C., the loss of strain over a period of time indicates a decrease in elasticity of the hydrogels.
As for the higher degree of hydrolysis PVA hydrogel (i.e. 28-99,
Frequency Sweep
The effects of 9 month storage at 20° C. on storage (G′), loss (G″) moduli and loss tangent (G″IG′) for different PVA type blank hydrogels have been depicted in the individual graphs in
In the combined graphs shown in
As seen from
Re-Heating Experiments and Effect of Heating Time
To check whether the turbidity, pH drop and phase separation is reversible or not, 9 month old hydrogels were again re-heated to 85° C. for 30 minutes, cooled and observed for all above parameters. In addition, storage (G′) and loss (G″) moduli as well as hardness and compressibility were measured for re-heated hydrogels.
In
As can be seen in
All of the above observations suggest that the temperature is a major factor for the stability of the low degree of hydrolysis (88%) PVA hydrogels. The instability (in terms of colour, pH drop, acetic acid-like odour generation) caused by temperature is not reversible through reheating. A possible reason for such behaviour could be that the presence of acetic acid may accelerate PVA degradation.
To further investigate these findings, additional blank hydrogels were prepared as per the composition displayed in Table 4 below with different heating times at 85° C. Two PVA hydrogels were prepared (26-88 and 28-99) by heating at 85° C. for 1, 2 and 3 hr.
Table 4 below shows that higher degree of hydrolysis (99%) PVA hydrogels (28-99) are stable without any turbidity, acetic acid-like odour and phase separation even after 3 hr heating. However, the lower degree of hydrolysis (88%) PVA hydrogels (26-88) were not stable after heating for 3 hr at 85° C. They exhibited a slight acetic acid-like odour after 2 hr heating and complete phase separation with strong acetic acid-like odour after 3 hr heating. This set of experiments further confirmed that low degree of hydrolysis (88%) PVA hydrogels (26-88) are susceptible to higher temperature. In addition, all above experiments once again proved superiority of higher degree of hydrolysis (99%) PVA hydrogels as they are stable without noticeable change in physicochemical properties. 28-99 PVA have negligible amounts (<1%) of acetate groups which practically eliminates the possibility of hydrolysis over a period of time. The resultant 28-99 hydrogels are the same as that of fresh hydrogels in various physicochemical properties even after 9 months and did not show any substantial change after heating for 3 hours.
Stability batches were prepared as per the procedure described in EXAMPLE 1 above and the composition shown in Table 5 below. A brief description of the time points, stability condition and number of containers per condition are given in Table 6 below.
Tests carried out: Weight change *, pH *, Lidocaine Assay #, Rheology #, Hardness and compressibility *, In vitro release study †
The 28-99 PVA hydrogels (batch numbers 16 and 17 in Table 5 above) were evaluated for various parameters up to 6 months storage. The same parameters for batch numbers 18 and 19 (4-88 PVA) up to the 3 month time point are also discussed.
Batch numbers 16 (28-99, 30° C./65 RH) and 17 (28-99, 20° C. uncontrolled RH):
The results of the stability batches are summarised in Table 7. Assay of lidocaine HCl by HPLC showed minor fluctuations (minor increases and decreases) over the 6 months of the study, with no appreciable trends. This indicates that the drug is stable in PVA-THB hydrogels over 6 months without any degradation. Weight loss was observed to increase over a period of time at both storage conditions. However, weight loss is very small and did not substantially affect the final composition of the hydrogels.
Changes in pH were negligible over the study and were typically within the error of the measurement. The hardness and compressibility of batch number 17 (28-99 PVA hydrogels at 20° C. uncontrolled RH) remains fairly consistent, in comparison to the 4-88 hydrogels, over the duration of the study.
Storage and loss moduli were determined using oscillatory rheometry. A frequency stress sweep was performed at a defined stress of 60 Pa between 0.1 and 10 Hz at 25° C. and storage (G′) and loss (G″) moduli are graphically presented in
In vitro release of lidocaine HCl for batch numbers 16 (30° C./65 RH) and 17 (20° C./RH uncontrolled) after 0, 3 and 6 month storage are graphically depicted in
Batch numbers 18 (4-88, 30′C/65 RH) and 18 (4-88, 20° C. uncontrolled RH):
The results of the stability batches are summarised in Table 7. The assay of lidocaine HCl by HPLC showed minor fluctuations over the 3 month study. This indicates that the drug is stable in both 28-99 and 4-88 PVA-THB hydrogels up to 3 months without substantial degradation. Weight loss was observed to increase over a period of time at both storage conditions (20° C. uncontrolled humidity and 30° C./65 RH). The weight loss associated with 30° C./65 RH storage condition (Batch number 18) was slightly higher than that associated with 20° C. storage condition. However, the weight loss observed was very small and did not substantially affect the final composition of the hydrogels.
The pH was observed to drop over a period of time for both storage conditions. The magnitude of the reduction was greater at 30° C./65 RH compared to 20° C. The hardness and compressibility of 4-88 hydrogels (batch numbers 18 and 19) at both storage conditions continued to drop considerably over the 3 months storage. However, the magnitude of such decrease was lower at 20° C. compared to 30° C./65 RH.
Frequency sweep results for 4-88 stability batches (18 and 19) are presented in
In vitro release of lidocaine HCl for batch numbers 18 (30° C./65 RH) and 19 (20° C. uncontrolled) after 0 and 3 months storage are graphically depicted in
In conclusion, low degree of hydrolysis (88%) PVA blank hydrogels exhibited turbidity, phase separation and an acetic acid-like odour. The occurrence of such changes seemed to be related to the degree of hydrolysis of the PVA chains. No such changes were observed for higher degree of hydrolysis (99%) PVA blank hydrogels. Re-heating experiments confirmed that such changes for 88% hydrolysed PVA hydrogels are not reversed by simple heating and mixing. The effect of heating time while preparing fresh hydrogels, showed that temperature is the main culprit for the stability of the low degree of hydrolysis (88%) PVA hydrogels. Excessive heating at 85° C. can cause the fresh 88% hydrolysed PVA hydrogels to de-mix. It was proposed that these changes are attributed to hydrolysis of the residual acetate groups on PVA chains liberating acetic acid decreasing the pH and resulting in phase separation through an unknown mechanism. If the liberated acetic acid can cause degradation of PVA chains, the resultant degraded PVA chains and disturbed ionic interaction may precipitate the less soluble products to generate turbidity.
Lidocaine HCl is stable in both 28-99 and 4-88 PVA-THB hydrogels with no appreciable degradation. Storing gels above 20° C. caused a decrease of storage (G′) and loss (G″) moduli, hardness and compressibility and pH. These observations suggest that the ideal storage condition for the gels is 20° C. Overall stability results for lidocaine HCl loaded PVA-THB hydrogels showed that higher degree of hydrolysis hydrogels are superior than lower degree of hydrolysis PVA hydrogels in almost all physicochemical properties and that lidocaine HCl is generally stable in the formulation at 20° C.
Lidocaine loaded gels were manufactured as follows:
Borax, D-mannitol and lidocaine were weighed in individual weigh boats and these powders were added to a pre-weighed 250 ml glass jar. De-ionised water was added and the contents of the jar thoroughly mixed. 20% PVA stock solution was added, the lid was closed and the contents of the jar swirled to mix thoroughly before being brought up to final weight using de-ionised water. The jar and its contents were placed in a pre-heated 60° C. water bath and the heat turned to 85° C. The mixture was stirred periodically and once homogenous, it was maintained in the 85° C. water bath for a further 30 minutes. The suspension was brought up to final weight using de-ionised water and stirred briefly to fully absorb the water before being split into containers (20 g of gel per container) for testing.
Autoclaving was conducted using a 200 L Front Loading Steam Autoclave by Priorclave, programmed for a USP sterilisation cycle of 121° C. for 15 minutes. To ensure the water in the gels did not evaporate, the autoclave was set at 3 bar pressure.
Method of Analysis
Rheometric analysis of 10 gel samples, before and after autoclaving, was carried out using a Kinexus Pro rotational rheometer (Malvern Instruments Ltd., Worcestershire, UK). Storage modulus (G′), loss modulus (G″) and complex modulus (G*) were measured following an oscillation stress sweep to determine the linear viscoelastic region. The crossover modulus (where the G′ and G″ cross) was reported.
Results
The viscosity and appearance results for the gels (n=10) tested before and after autoclaving is detailed in Table 8 below.
There was no significant difference between the viscosity of the gels before and after autoclaving. Furthermore, the gels before and after autoclaving were visually equivalent.
Lidocaine loaded gels were manufactured as above in both polypropylene and glass containers and according to the following tables:
Autoclaving was conducted using a 200 L Front Loading Steam Autoclave by Priorclave, programmed for a USP sterilisation cycle of 121° C. for 15 minutes. To ensure the water in the gels did not evaporate, the autoclave was set at 3 bar pressure.
Glass and polypropylene containers are widely used packaging in autoclaves. There was no significant container effect on the stability of the gels after autoclaving.
Method of Analysis
Tackiness was assessed by touch. Prior to sterilisation the gels have no tack. Upon reduction in stability, the gels become sticky and pressing a finger onto the surface and removing it is a simple way to test tackiness. Clarity and air bubbles were assessed visually. All gels prepared were colourless and very transparent, so air bubbles were readily apparent.
Analysis of the shear modulus was carried out using a Kinexus Pro rheometer (Malvern Instruments Ltd., Worcestershire, UK) on all hydrogel formulations. Tests were carried out at 25° C.±0.2° C. using 20 mm diameter stainless steel parallel plate geometry and a working gap of 1-2 mm. The linear viscoelastic region (LVR) of the PVA-borate hydrogel formulation was determined by an amplitude sweep (0.01-100% strain at a frequency of 1.0 Hz). All measurements of the shear modulus were performed within the LVR.
As is clear from Tables 10a and 10b, the shear modulus of lidocaine loaded gels made from 88% hydrolysed PVA decreases upon attempted sterilisation.
As is clear from Tables 11a and 11b, lidocaine loaded gels made from 99% hydrolysed PVA show essentially no difference in shear modulus upon heat sterilisation. Therefore gels according to the invention can be sterilised whilst gels prepared with a lower degree of hydrolysis cannot.
Lidocaine loaded gel was prepared as described above in Examples 3 and 4.
A 5 g sample of lidocaine loaded gel was placed onto the foot of a patient with an underlying painful Morton's neuroma. The gel was placed onto the top of the foot adjacent the fourth toe. A gauze support (Mepore®) was used to hold the gel in place for 4 hours. After this period of time, the gauze was removed and the patient did not report any sensation of pain from the neuroma.
Aspects of the present invention have been described by way of example only and it should be appreciated that additions and/or modifications may be made thereto without departing from the scope thereof as defined in the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 1719982.9 | Nov 2017 | GB | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | 15733086 | May 2020 | US |
| Child | 18228476 | US |
