the technology related to the present invention involves use of a thermo - responsive hydrogel . thermo - responsive hydrogels form swollen states after they absorb water , active ingredients ( e . g ., the active ingredients of the present invention ) and other substances . the hydrogels of the present invention release the contents when the temperature is above about 32 ° c . this is because the hydrogels of the present invention shrink at temperatures of about 32 ° c . thereby causing the discharge ( release ) of the absorbed substances . the rate of discharge is proportional to the rate of shrinkage of the hydrogel particle , which is dependent upon the temperature , the size of the hydrogel particle ( for example , surface to size ratio and rate of temperature change affect release rate ) and composition of the hydrogel ( for example , crosslinking affects release rate ). hence , the release process is coupled with the hydrogel shrinking process and , therefore , the discharge rate can be controlled . besides the property of sustained release , the present invention provides users enhanced cooling feeling that is caused by co - effect of menthol and water contained in a hydrogel matrix . under the above - mentioned situation , the inventors of the present invention made an intensive study . as a result , the present inventors found that a sustained - release nasal composition which comprises a wax / petroleum jelly base , a hydrogel polymer , and invigorating , anti - fatigue compounds ( menthol and menthone ) can achieve the above objective . when the composition is applied on the skin , the composition comprising a hydrogel that contains a high concentration of menthol and / or menthone releases the menthol and menthone slowly thereby proving invigorating and anti - fatigue effects for at least about 1 hour and for more than about 2 hours . the active ingredients of the present invention are menthol and menthone . the concentration of menthol and / or menthone in the composition of the present invention is from approximately 0 . 1 % by weight to approximately 10 % by weight , approximately 0 . 2 % wt . to approximately 5 % wt ., approximately 0 . 4 % wt . to approximately 2 . 5 % wt . and approximately 0 . 6 % wt . to approximately 2 . 0 % wt . in another embodiment , the menthol and / or menthone that are used are components of one or more essential oils such as , for example , peppermint oil . peppermint essential oil can contain as much as about 85 % vol . menthol and / or menthone although concentrations in the 20 % to 50 % range are more typical . peppermint essential oil is available commercially . see , for example , products by plant therapy essential oils , twin falls , id . the percent of hydrated hydrogel polymer in the composition of the present invention is ( by weight percent ) from approximately 1 % to approximately 20 %, approximately 4 % to approximately 16 %, approximately 8 % to approximately 12 %. the invigorating compounds ( active ingredients ) used in the present invention are shown in the following formulas : the thermo - responsive hydrogel used in the present invention includes gels made of poly ( n - isopropylacrylamide ) [ polynipam or pnipa ] ( see , park and hoffman , 1994 , j . applied polymer sci ., 52 : 85 - 89 ) its derivatives ( e . g ., acrylamide derivatives involve changing r groups in the formula , and its copolymer derivatives ( e . g ., t - butylacrylamide is one of the monomers that can be used to copolymerize polynipam and shift the phase transition at lower temperature ), polylactic acid ( pla ) polyethylene glycol ( peg ), polylactic - co - glycolic acid ( plga ), polycaprolactone ( pcl ) and polypeptides . the hydrogel polymers or copolymers can be used individually or in combinations of two or more . hydrogel particles range in size from approximately 50 nm to approximately 0 . 5 mm . hydrogel particles in various sizes can release liquid content at different rates and for different lengths of time and thereby contribute to the sustained - release feature of the present invention . the hydrogel polymer may be crosslinked with crosslinking agent added in the range of 0 %- approximately 10 % of the dry weight of the polymer ( hydrogel ) used . methylenebisacrylamide ( mba ) is an example of a suitable crosslinking agent and was used in the examples given herein . other suitable crosslinking agents are known to those of ordinary skill in the art . in the examples given herein , approximately 2 % crosslinking agent was added to the hydrogel . the purpose of crosslinking is to build up a hydrophilic network which is suitable for containing a large amount of active ingredients and water . although crosslinking is not essential to the present invention , its use is preferred . for the production of an ointment , cream or balm the composition of the present invention is formulated with an ointment base . spray formulations would not require an ointment base . the production of ointment bases is known to those of ordinary skill in the art . the ointment base used in the present invention may include one or more of petrolatum , bee &# 39 ; s wax , plastibase , paraffin , silicone , petroleum jelly and the like . these ointment base ingredients may be used individually or in combination of two or more . the amount of the ointment base used is not particularly restricted , but falls within the range of approximately 50 % - approximately 95 % by weight and preferably approximately 75 % - approximately 90 % by weight based on the total weight of the ointment . menthone and menthol are used in an amount for providing invigorating benefits and relieving drowsiness symptoms , as disclosed herein . for example , the concentrations of menthone are from 0 . 1 % to 10 % and menthol from about 0 . 1 % to 10 %, each . the suitable ratio between menthone and menthol ( menthone : menthol ) was also determined to be appropriately 2 : 1 to 5 : 1 . other ratios have also been shown to work however with reduced effectiveness . the total amount of menthone and menthol to achieve maximum invigorating effect was determined by extensive research and was not predictable to one of ordinary skill in the art . one of ordinary skill in the art , with the aid of the teachings of the present invention , may make further refinements to the present invention without undue experimentation . known additives such as flavors , spices , coloring agents , surfactants and the like may be added to the sustained - release invigorating ointment according to the present invention unless the addition adversely affects the present invention . examples include , but are not limited to , oils ( e . g ., coconut oil , almond oil ), fragrance and colors . water ( e . g ., purified ) may also be included in the composition if desired or needed for solubility of components , rehydration of the hydrogel , adjustment of moisture content and / or adjustment of viscosity . other essential oils are known to contain menthol and menthone and are also useful in the present invention . one of ordinary skill in the art , with the guidance provided by the present specification , may incorporate one or more of these essential oils into the present invention without undue experimentation . these include , but are not limited to , allspice , angelica root , anise star , aphrodisiac blend , basil , bay , bergamot , birch , black pepper , blood orange , breathe easy blend , cajeput , camphor , cananga , caraway , cardamom , carrot , cassia , cedarwood , chamomile ( german ), chamomile ( roman ), cinnamon bark , cinnamon leaf , citronella , clary sage , cleaning blend , clementine , clove , cocoa absolute , cognac , copaiba , coriander , cumin , cypress , cypriol , davana , dill weed , elemi , eucalyptus , fennel , fir needle , frankincense , french lavender , galbanum , geranium , ginger , grapefruit , helichrysum , ho wood , hydacheim , hyssop , invigorate blend , jasmine absolute , juniper berry , kanuka , key lime , lavender , lemon , lemon eucalyptus , lemon myrtle , lemongrass , lime , litsea , mace , mandarin , manuka , meditation blend , melissa , myrrh , myrtle , neroli , nerolina , niaouli , nutmeg , oregano , origanum , palmarosa , palo santo , parsley , patchouli , penny royal , peppermint , peru balsam , petitgrain , pimento , pine , ravensara , relaxation blend , renew blend , rose absolute ( bulgarian ), rose absolute ( moroccan ), rose geranium , rosemary , rosewood , sage , sandalwood ( australian ), sandalwood ( indian ), sensation blend , spearmint , spikenard , spruce , stress relief blend , sweet marjoram , sweet orange , tagates , tangerine , tansy , tarragon , tea tree , thyme , turmeric , valerian , vanilla , verbena , vetiver , wintergreen , yarrow and ylang ylang . according to the present invention , the sustained - release invigorating composition ( e . g ., ointment , cream , balm , spray , etc .) of the present invention can be used by inserting it ( placing it ) into the nose ( into the nasal cavity ) or on the skin around and / or under the nose . it can also be used by the same application method for known lip balms . for example , the composition can be spread or otherwise applied to the lips . further , the present invention can be formulated into nasal sprays by methods known to those of ordinary skill in the art and without undue experimentation . for example , reduction or elimination of the ointment base would result in a suitable nasal spray formulation . the method for producing ( formulating ) the sustained - release invigorating compound of the present invention has no particular restriction . any suitable methods known to those of skill in the art can be employed to produce the composition of the present invention and are incorporated herein by reference . for example , the ointment of the present invention can be produced by a method ordinarily used in the field or by an appropriate combination of two or more methods . specifically , the ointment can be produced by simple mixing of individual components , e . g ., a base such as an ointment base , one or more suitable hydrogels , menthol and / or menthone , water and any non - active ingredients ( as indicated , supra ), if desired . in one embodiment , the base is first produced , hydrated hydrogel ( hydrogel and water ) is added next and then peppermint oil is added . non - active ingredients are added simultaneous with or sequential to the peppermint oil . in yet another embodiment , the menthone and menthol ( either as components of peppermint oil or other essential oils or as isolated or purified chemicals ) are formulated with the hydrogel ( crosslinked or not crosslinked ) prior to being formulated with the other ingredients of the composition . commercial batch mixing equipment may be utilized and the product then formed into suitable sized and shaped units simultaneously with or sequentially with packaging and instructions for use . in another method of production , the active ingredients are first mixed with the hydrogel prior to mixing with the other ingredients . in addition to being formulated as an ointment , the composition of the present invention may be formulated into a lip balm - type product . this can be achieved by , for example , increasing the amount of paraffin or wax , for example , in the base formulation . further , the composition of the present invention may be formulated as a liquid for use as , for example , a nasal spray . formulations are produced at room temperature and ideally below about 30 ° c . to limit or eliminate the release of active ingredients from the hydrogel . this example demonstrates the results of a vaporization test conducted for the sustained - release invigorating ( anti - fatigue ) composition of the present invention . in order to confirm the sustained - release properties of the sustained - release invigorating composition of the present invention the following test was conducted in a temperature controllable incubator . approximately 0 . 2 g of a sustained - release ointment of the present invention was spread on the surface of a plastic weighing plate . the weighing plate was put on an analytical scale in the incubator . as a control , an ointment without hydrogel ( the formula is the same as sustained - release ointment except that no hydrogel was in it : in other words , the active ingredients , although present , were not incorporated in the hydrogel particles ) was also tested in the same procedure as described above . the test was conducted at 35 ° c .± 0 . 5 ° c . from the start of the test to 120 minutes the weight of ointment was monitored at intervals of 5 minutes . the results of the above test are shown in fig2 . as shown in the results , the sustained - release invigorating ointment of the present invention exhibits such advantages that the menthone and menthol contained in the ointment with hydrogel is released over a long period of time . at 35 ° c ., it took 40 minutes to release 50 % of the invigorating contents in the ointment . as comparison , it took only 11 minute to release 50 % percentage invigorating contents for ointment without hydrogel . as shown in fig3 , in the control ointment 50 % menthone were released within the first 10 minute . there was no release of menthone after 50 minutes according to this test . however , for the sustained - release ointment of the present invention , the release process ( i . e ., release of menthone ) lasts more than 110 minutes . even after 110 minutes there was still about 23 % active ingredient reserved in the ointment . test formulation : ointment base ( 4 g ), peppermint oil ( 0 . 2 g ), hydrated pnipa hydrogel ( 0 . 4 g : 10 % hydrogel , 90 % water ). the ointment base comprised about 20 % paraffin and / or beeswax and about 80 % castor oil . the wax was melted , mixed with the castor oil and cooled . this test formulation comprised approximately 0 . 4 %- 2 . 5 % menthol / menthone . in brief , the polynipam was synthesized in acetonitrile solvent in following manner : about nipa 97 %, azobisisobutyronitrile ( aibn ) about 1 . 5 %, mba about 2 % at 65 ° c . for 24 hr . the synthesized pnipam was dialyzed , dried and grinded into white powder . the pnipam powder , water , menthone and menthol ( constituents of the peppermint oil ) were blended . the hydrated mixture was blended with an ointment base and then formed and packaged into balm stick or other packaging container . control formulation : ointment base ( 4 g ), peppermint oil ( 0 . 2 g ), 360 mg h 2 o ( equal amount of water as contained in hydrogel in test formulation ). this control formulation comprises approximately 0 . 4 %- 2 . 5 % menthol / menthone . in this example the release rate of active ingredients from the test composition ( ointment ) of the present invention as the result of temperature was tested . fig4 shows that the compsotion of the present invention releases active ingredients very slowly ( 56 ug / min at the begining 30 minutes ) at 22 ° c . ( c ). the release rate was 6 times higher ( 359 ug / min at the beginning 30 minutes ) at 36 ° c . ( c ). x - axis is time in minutes . y - axis is release is rate of release as a percent of total weight of the test composition . formulation of the test sample : ointment base ( 4 g ), peppermint oil ( 0 . 2 g ), hydrated pnipa hydrogel ( 0 . 4 g ). this test formulation comprises approximately 0 . 4 %- 2 . 5 % menthol / menthone . in this experiment the effectiveness of the composition of the present invention was tested . two groups of subjects were used . in group one the ointment of the present invention was applied externally under the nose or on the upper lip . the test population was 12 adults . after application of the product they were asked following questions : does the product keep you awake ? 8 answered yes . 4 answered not sure . in group two the ointment of the present invention was applied inside nose . the test population was 8 adults . eight of 8 felt invigorated . eight out of 8 felt it was effective to keep them awake . control subjects did not report any invigoration or increased wakefulness .
the present invention relates to a thermo - responsive hydrogel polymer formulated with one or more active agents selected from the group consisting of menthol and menthone , wherein said active agents are effective in invigorating the user and / or effective in relieving fatigue .