WO2008017127A1

WO2008017127A1 - A method for detecting a pharmaceutically active agent

Info

Publication number: WO2008017127A1
Application number: PCT/AU2007/001128
Authority: WO
Inventors: Scott Flower; Michael Sherburn
Original assignee: A Capital Idea (Act) Pty Ltd
Priority date: 2006-08-10
Filing date: 2007-08-10
Publication date: 2008-02-14

Abstract

The present invention relates to methods of detecting the presence or absence of therapeutically active agents in liquid, gaseous or aerosol pharmaceutical compositions by colorimetric detection, especially inhalable compositions. The invention also relates to containers or packaging comprising a means of detecting the presence or absence of a therapeutically active agent in a liquid, gaseous or aerosol pharmaceutical composition.

Description

A METHOD FOR DETECTING A PHARMACEUTICALLY ACTIVE AGENT

Field of the Invention

Background of the Invention

A means of determining whether a therapeutically active agent is present in a pharmaceutical composition during or after manufacture of the composition can provide important quality control information for a manufacturer and assurance for a consumer that the composition contains the required medication. This can be particularly important with therapeutically active agents that, if not administered at the required time, may result in severe illness or death.

The absence of a therapeutically active agent may be the result of a manufacturing fault, a fraudulent pharmaceutical manufacturer or because the number of doses in the original composition have been consumed.

In 1998, a pressure metered dose inhaler asthma medication that contained no active agent was released onto the US market. Although the faulty products were recalled, an inquiry found that these products had contributed to the deaths of 17 asthma sufferers between 1998 and 2001.

There is a need for a simple means of detecting the present or absence of a therapeutically active agent. Summary of the Invention

The present invention is predicated in part on the use of colorimetric reactions to determine the presence or absence of a therapeutically active agent in a pharmaceutical composition.

Description of the Invention

In one aspect of the present invention there is provided a method of detecting the presence or absence of an active agent in a liquid, gaseous or aerosol pharmaceutical composition, wherein the active agent comprises a functional group that is not present in other components of the composition; said method comprising

i) applying the composition to a substrate impregnated with a colorimetric reagent capable of reacting with the functional group;

ii) observing the colour of the substrate.

The observation of a colour change in the substrate detects the presence of an active agent. The observation of a lack of colour change in the substrate detects the absence of an active agent.

The methods of the invention allow determination of whether a therapeutically active agent is present in a liquid, gaseous or aerosol composition. The therapeutically active agent can be any agent that contains a functional group capable of reacting with a colorimetric reagent and resulting in a colour change. To avoid false positive results, it is important that the functional group is unique to the therapeutically active agent and does not occur in any other component of the composition. For example, other components may include therapeutically active compounds present in the composition other than the active compound that is to be detected, or pharmaceutically acceptable carriers, excipients, diluents and/or adjuvants in a pharmaceutical composition. Suitable active agents include those that can react with a colorimetric reagent to cause a visible colour change. For example, suitable active agents are those that can form coloured complexes with metal ions or undergo a colour change when treated with oxidising agents or conjugating agents. For example, suitable active agents include, but are not limited to, those that have functional groups such as phenols, enols, ketones, enones, alcohols, esters, amines, thioesters and carboxylic acids. Exemplary active agents include, but are not limited to, 2-(l , 1 -dimethylethyl)amino- 1 -(4-hydroxy-3-hydroxymethylphenyl)ethanol (salbutamol), [6,9-difluoro- 17-(fluoromethylsulfanylcarbonyl)- 11 -hydroxy- 10,13,16- trimethyl-3-oxo-6,7,8,9, 10, 11 , 12, 13 , 14, 15, 16, 17-dodecahydrocyclopenta[a]phenanthren- 17-yl]propionate (Flixotide™), 9-chloro-l l-hydroxy-10,13,16-trimethyl-3-oxo-17-[2- propionyloxyacetyl]-6,7,8, 11, 12, 14, 15,16-octahydrocyclopenta[a]phenanthren- 17- yl]propionate (beclamethasone dipropionate, Quar™, Becotide™), 3-(3-hydroxy-l-oxo-2- phenylpropoxyl)-8-methyl-8-(l-methylethyl)-8-azonabicyclo(3.2.1)-octane bromide

(ipratropium bromide, Atrovent Forte™), (16α,17α-22R,S-propylmethylenedioxypregna- l,4-diene-l lβ,21-diol-3,20-dione (Pulmicort™) and pharmaceutically acceptable salts thereof.

Suitable pharmaceutically acceptable salts thereof include, but are not limited to, salts of pharmaceutically acceptable inorganic acids such as hydrochloric, sulphuric, phosphoric, nitric, carbonic, boric, sulfamic, and hydrobromic acids, or salts of pharmaceutically acceptable organic acids such as acetic, propionic, butyric, tartaric, maleic, hydroxymaleic, fumaric, malic, citric, lactic, mucic, gluconic, benzoic, succinic, oxalic, phenylacetic, methanesulphonic, toluenesulphonic, benzenesulphonic, salicylic, sulphanilic, aspartic, glutamic, edetic, stearic, palmitic, oleic, lauric, pantothenic, tannic, ascorbic acid and valeric acids.

Base salts include, but are not limited to, those formed with pharmaceutically acceptable cations, such as sodium, potassium, lithium, calcium, magenesium, zinc, ammonium, alkylammonium such as salts formed from triethylamine, meglumine, alkoxyammonium such as those formed with ethanolamine and salts formed from ethylenediamine, choline or amino acids such as arginine, lysine or histidine. Basic nitrogen-containing groups may be quartenised with such agents as lower alkyl halide, such as methyl, ethyl, propyl, and butyl chlorides, bromides and iodides; dialkyl sulfates like dimethyl and diethyl sulfate; and others.

In a preferred embodiment, the active agent contains a phenol or enol functional group and is in a liquid, gaseous or aerosol composition. In a particularly preferred embodiment, the phenolic compound is salbutamol and pharmaceutically acceptable salts thereof.

In the methods of the invention, the colorimetric reaction is allowed to take place on a substrate that is impregnated with a colorimetric reagent that will change colour when exposed to the therapeutically active agent. Suitable substrates include paper, such as absorbent paper, natural or synthetic fabrics, or polymer films. The substrate may be impregnated with the colorimetric reagent by any suitable means, for example, immersing the substrate in a solution of the colorimetric reagent or coating the substrate with a solution of or aerosols of the colorimetric reagent. The substrate may then be dried if required or may be used wet.

The colorimetric reagent may be any compound that is one colour before exposure to the functional group of the therapeutically active agent and a visibly different colour after exposure to the functional group of the therapeutically active agent. By the term "visibly different" is meant that the colour change may be observed by the human eye. Suitable colorimetric reagents include metal salts that form a coloured complex with the functional group of the therapeutically active agent or conjugating agents or oxidising agents that react with a functional group of the therapeutically active agent causing a colour change.

A suitable colorimetric reagent for detecting compounds containing phenolic or enolic groups is ferric chloride (FeCl₃).

In some cases, the colorimetric reaction will occur immediately resulting in immediate detection of the presence of the therapeutically active agent. In other cases, a period of time such as seconds or minutes, may be required for the development of colour. It is preferred that the colorimetric reaction occurs e.g. within 30 seconds, preferably within 20 seconds, more preferably within 15 seconds and still more preferably within 10 seconds or immediately upon contact. However if a period of colour development is required, the instructions provided with the method may specify a period of time to allow development of colour, where the lack of colour change after the stated period indicates the absence of the therapeutically active agent.

In the method of the invention, the appearance of a colour change indicates the presence of the therapeutically active agent to be detected. The absence of a colour change indicates the absence of the therapeutically active agent to be detected.

The pharmaceutical composition may be applied to the substrate by any suitable means. For example, liquid, aerosol or gaseous compositions may be sprayed onto the substrate. A liquid composition may also be applied using a dropper or by pouring over the substrate.

If the substrate and colorimetric reagent are non-toxic or the colorimetric reagent does not leach out of the substrate when wet, the impregnated substrate may be dipped or immersed in a liquid composition.

In a preferred embodiment of the invention the therapeutically active agent is salbutamol in an inhalable composition and the colorimetric reagent is ferric chloride. Therefore the present invention also provides a method of detecting the presence or absence of an inhalable salbutamol composition in a pressurised metered dose inhaler, said method comprising

i) applying the inhalable salbutamol composition to a substrate impregnated with ferric chloride;

ii) observing the colour of the impregnated substrate. In this particular embodiment, the impregnated substrate is initially pale yellow. If salbutamol is present the substrate darkens to give a black colour within about 10 seconds. If no salbutamol is present, the substrate remains pale yellow.

The ferric chloride may be present in any amount that provides a visible colour change. Typically at concentrations below 0.1 M the colour change is difficult to detect. However, concentrations greater than 0.1 M up to saturated solutions gave adequately visibly detectable colour changes.

The method of the invention may be used by a manufacturer to confirm that a pharmaceutical composition contains the desired active agent before it is released for market as a quality control measure. The method of the invention may also be used by a consumer before using the composition to ensure the presence of the required therapeutically active agent or periodically during use to confirm that therapeutically active agent is still present or to confirm that all of the dosages have been consumed. Determining whether all dosages have been consumed may be particularly important in inhalable compositions that are delivered by a pressurised metered dose inhaler. In this case, multiple doses are contained in one inhaler unit, the volume of doses remaining is not visible and the propellant used in the composition is incorporated in greater quantities than for the doses required. This may lead to a consumer continuing to use an inhaler after all of the therapeutic doses have been consumed.

The inhaler may be any inhaler capable of dispersing an aerosol or gaseous therapeutically active agent. For example, inhalers currently used to dispense asthma medication, especially pressurised metered dose inhalers. Optionally the inhaler may include a dose counter, which may be digital or mechanical.

A package containing a single unit or multiple units of the impregnated substrate suitable for determining the presence or absence of a specific therapeutically active agent may be sold to a manufacturer or consumer optionally together with written instructions, for example, indicating how to apply the pharmaceutical composition, the length of time required for the colorimetric reaction to occur, how to determine whether the therapeutically active agent is present or absent.

The invention also relates to a kit comprising a container including the pharmaceutical composition together with one or more units of substrate impregnated with colorimetric reagent. In a preferred embodiment, the kit may contain a pressurised metered dose inhaler containing an inhalable pharmaceutical composition comprising salbutamol and one or more units or patches of absorbent paper impregnated with an aqueous solution of ferric chloride.

Each unit or patch may be any appropriate size. For example, a unit or patch may be a suitable size for handling by a manufacturer of pharmaceutical compositions or by a consumer. For example, a convenient size may be between 1 and 5 cm in two dimensions, such as 1 x 1 cm, 1 x 2 cm, 1 x 3 cm, 1 x 4 cm, 1 x 5 cm, 2 x 2 cm, 2 x 3 cm, 2 x 4 cm, 2 x 5 cm, 3 x 3 cm, 3 x 4 cm, 3 x 5 cm, 4 x 4 cm, 4 x 5 cm, or 5 x 5 cm. Alternatively the substrate impregnated with the colorimetric reagent may be mounted on an inert support preferably larger than the substrate. For example, a cardboard or plastic support may be used to provide an inert handling zone which may be held while preparing to use the method of the invention, during use of the method and/or after the use of the method such as during disposal. An inert handling zone allows the method to be used without the user contacting the impregnated substrate.

In another aspect of the invention, one or more units of substrate impregnated with colorimetric reagent may be incorporated into the container or part of the container comprising the pharmaceutical composition. In such cases the unit may be protected from contact with the environment, the composition or the user of the composition by a protective coating. For example, a removable adhesive cover may be used. In some embodiments the cover may be removed or partially removed to carry out the method of the invention and replaced after the method steps have been completed. The unit of substrate impregnated with colorimetric reagent may be positioned on any convenient part of the container. For example, the exterior of the container or its lid or inside the lid or container. In a preferred embodiment, the container is a pressurised metered dose inhaler and the unit of substrate impregnated with the colorimetric reagent is located on the mouth piece cover of the inhaler.

In another aspect of the invention, there is provided a container for delivering a liquid, gaseous or aerosol pharmaceutical composition comprising a substrate impregnated with a colorimetric reagent capable of reacting with a functional group in an active agent in the pharmaceutical composition.

In a preferred embodiment of the invention, there is provided an inhaler for delivering an inhalable salbutamol composition comprising a substrate impregnated with ferric chloride.

Preferably the therapeutically active agent is salbutamol in an inhalable composition within a pressurised metered dose inhaler and the substrate is impregnated with ferric chloride and located on a detachable mouth piece cover of the inhaler, preferably protected from the environment by a removable protective cover.

Throughout this specification and the claims which follow, unless the context requires otherwise, the word "comprise", and variations such as "comprises" and "comprising", will be understood to imply the inclusion of a stated integer or step or group of integers or steps but not the exclusion of any other integer or step or group of integers or steps.

Further features of the invention are more fully described in the following Example(s). It is to be understood, however, that this detailed description is included solely for the purposes of exemplifying the present invention, and should not be understood in any way as a restriction on the broad description as set out above. EXAMPLES

Example 1

Preparation of the impregnated substrate A piece of absorbent paper was impregnated with ferric chloride by dipping the absorbent paper into an aqueous solution of ferric chloride (at least 0.1 M concentration) to provide a substrate that is pale yellow in colour. The substrate was allowed to dry.

In an alternative method, solid ferric chloride hexahydrate was applied directly to the paper. Ferric chloride hexahydrate is a waxy solid that when rubbed onto or across a substrate leaves a residue that is sufficient to provide a colorimetric reaction.

Example 2

Application of pharmaceutical composition An inhalable pharmaceutical composition comprising salbutamol contained in a pressurised metered dose inhaler was obtained and applied to the impregnated substrate prepared above by releasing a single dose from the inhaler so that the composition contacted the impregnated substrate.

Upon contact of the dosage of salbutamol, the pale yellow substrate developed a black colouration within 10 seconds. The change of colour from yellow to black indicated the presence of salbutamol.

Example 3 Application of inhalable propellants and carrier's

Example 2 was repeated using a pressurised metered dosage inhaler that contained inhalable propellants and carriers used in a salbutamol inhalable composition but without the presence of salbutamol.

Upon contact of the dose of composition, although the substrate became moist, no discolouration of the substrate occurred, the substrate remained pale yellow.

Claims

THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

1. A method of detecting the presence or absence of an active agent in a liquid, gaseous or aerosol pharmaceutical composition, wherein the active agent comprises a functional group that is not present in other components of the composition; said method comprising

ii) observing the colour of the substrate.

2. A method according to claim 1, wherein the active agent comprises at least one functional group selected from phenols, enols, ketones, enones, alcohols, esters, amines, thioesters and carboxylic acids.

3. A method according to claim 2, wherein the active agent comprises a phenol or enol functional group.

4. A method according to claim 1, wherein the active agent is selected from 2-(l,l- dimethylethyl)amino-l-(4-hydroxy-3-hydroxymethylphenyl)ethanol (salbutamol), [6,9-difluoro- 17-(fluoromethylsulfanylcarbonyl)- 11 -hydroxy- 10, 13, 16-trimethyl-3 - oxo-6,7,8,9, 10, 11 , 12, 13 , 14, 15 , 16, 17-dodecahydrocycloρenta[a]phenanthren- 17- yl]propionate (Flixotide™), 9-chloro-l l-hydroxy-10,13,16-trimethyl-3-oxo-17-[2- propionyloxyacetyl] -6,7,8, 11, 12,14, 15,16-octahydrocyclopenta[a]phenanthren- 17- yljpropionate (beclamethasone dipropionate, Quar™, Becotide™), 3 -(3 -hydroxy- 1- oxo-2-phenylpropoxyl)-8-methyl-8-(l-methylethyl)-8-azonabicyclo(3.2.1)-octane bromide (ipratropium bromide, Atrovent Forte™), (16α,17α-22R,S- propylmethylenedioxypregna-l,4-diene-l lβ,21-diol-3,20-dione (Pulmicort™) and pharmaceutically acceptable salts thereof.

5. A method according to claim 1, wherein the colorimetric agent is a metal salt that forms a coloured complex with the functional group of the therapeutically active agent or conjugating agents or oxidising agents that react with a functional group of the therapeutically active agent causing a colour change.

6. A method according to claim 3, wherein the colorimetric agent is ferric chloride.

7. A method of detecting the presence or absence of an inhalable salbutamol composition in a pressurised metered dose inhaler, said method comprising

ii) observing the colour of the impregnated substrate.

8. A container for delivering a liquid, gaseous or aerosol pharmaceutical composition comprising one or more units of a substrate impregnated with a colorimetric reagent capable of reacting with a functional group in an active agent in the pharmaceutical composition.

9. A container according to claim 8, further comprising a pharmaceutical composition capable of reacting with the colorimetric reagent.

10. A container according to claim 8, wherein the one or more units of substrate impregnated with colorimetric reagent are covered by a removable protective coating.

11. A container according to claim 8, further comprising a lid.

12. A container according to claim 11, wherein the one or more units of substrate are located on the exterior of the container or its lid.

13. A container according to claim 11, wherein the one or more units of substrate are located inside the lid of the container.

14. An inhaler for delivering an inhalable salbutamol composition comprising a substrate impregnated with ferric chloride.

15. An inhaler according to claim 14, wherein the inhaler is a pressurised metered dose inhaler.

16. An inhaler according to claim 14, wherein the substrate impregnated with ferric chloride is located on a detachable mouth piece cover of the inhaler.

17. An inhaler according to claim 16, wherein the substrate impregnated with ferric chloride is protected from the environment by a removable protective cover.

18. A kit comprising a container together with a pharmaceutical composition capable of reacting with a colorimetric reagent and one or more units of substrate impregnated with the colorimetric reagent.

19. A kit comprising an inhaler for delivering an inhalable salbutamol composition, an inhalable salbutamol composition and one or more units of substrate impregnated with ferric chloride.