histamine h 2 - antagonists have been used for a number of years in the treatment of duodenal and benign gastric ulceration , recurrent and stomal ulceration , esophageal reflux disease and other conditions where reduction of gastric acid has been shown to be beneficial , for example persistent dyspeptic symptoms with or without ulceration . the members of this class of medicines have a very bitter taste and palatability of oral compositions is a major consideration and has been a major problem in the preparation of liquid oral compositions . although the inclusion of a bitter tasting medicine in a coated tablet or within a capsule overcomes the problem of offensive taste , many adults and many children that have difficulty swallowing tablets or capsules cannot benefit from these dosage forms . solutions of histamine h 2 - antagonists have been found to be unpalatable . we have found that by preparing a solution of h 2 - antagonists with an alginate , a taste - masked composition is formed . the taste - masking is believed to result a complex being formed between the h 2 - antagonist and the alginate . the taste masking effect is augmented by the addition of sweetener , flavor , artificial sweetener enhancer and a humectant . it is clear that there has been a need for compositions of histamine h 2 antagonists which are liquid based and are palatable . histamine h 2 - antagonists are believed to be absorbed almost exclusively in the small intestine and liquid - based compositions offer the possibility that they could be absorbed more quickly and more efficiently than tablet compositions , particularly tablet compositions which have been coated to minimize unpleasant tastes . the composition of the present invention can be prepared by mixing an alginate dispersion in a humectant and preservative solution with a buffered solution of histamine h 2 antagonist then adding the sweetener , artificial sweetener enhancer ( optional ) and flavor then adjusting the ph to about 6 . 5 ± 0 . 5 and adding sufficient purified water to bring the solution to its final volume . a . water - soluble sweetening agents such as monosaccharides , disaccharides and polysaccharides such as xylose , ribose , glucose , mannose , galactose , fructose , dextrose , sucrose , sugar , maltose , partially hydrolyzed starch , or corn syrup solids and sugar alcohols such as sorbitol , xylitol , mannitol and mixtures thereof . b . water - soluble artificial sweeteners such as the soluble saccharin salts , i . e ., sodium , or calcium saccharin salts , cyclamate salts , acesulfam - k , ammonium glycyrrhizinate , dipotassium glycyrrhizinate and the like , and the free acid form of saccharin . c . dipeptide based sweeteners such as l - aspartylphenylalanine methyl ester and materials described in u . s . pat . no . 3 , 492 , 131 and the like . a water soluble sweetener ( a .) will usually be present in an amount corresponding to about 20 to 50 % w / v of the total composition , the amount depending in part upon whether other sweetener ingredients are present and the level of sweetness desired . when sugar is used as the sweetener , typically it is present from about 20 % to about 50 % w / v of the composition . it will be appreciated that combinations of sweeteners can be used . the sweetening agents when used , may also be used alone or in combination with each other . humectants such as glycerol and propylene glycol are present in the composition . typically the total quantity of humectant present is in the range of about 8 to 15 % w / v . thus , for example , propylene glycol and glycerol can each be present individually or in combination . an artificial sweetness enhancer may optionally be utilized in the present invention . when an artificial sweetness enhancer is utilized , it may be present in an amount from about 0 . 05 % to about 1 . 5 % w / v of the final composition . preferably , the artificial sweetness enhancer will be present in an amount from about 0 . 1 % to about 1 % w / v of the final composition . typical artificial sweetness enhancer would be pro sweet ® manufactured by the virginia dare company and sweet am ® from flavors of north america . it is preferred that the liquid compositions of the present invention contain preservatives to prevent microbial contamination . examples of preservatives are the alkylparabens , particularly methylparaben , propylparaben and butylparaben . the amount of preservative generally utilized will vary depending upon the preservative selected and may for example range from about 0 . 05 % to about 1 . 5 % w / v of the final composition . preferably , the preservative will be present in an amount from about 0 . 01 % to about 0 . 1 % w / v of the final composition . suitable flavorings include both natural and artificial flavors , and mints such as peppermint , menthol , artificial vanilla , cinnamon , various fruit flavors , both individual and mixed , and the like are contemplated . the flavorings are generally utilized in amounts that will vary depending upon the individual flavor , and may , for example , range in amounts of about 0 . 01 % to about 1 % by weight / volume of the final composition . preferably , the flavorants will be present in an amount of about 0 . 01 % to about 0 . 1 % w / v of the final composition . the flavorants include synthetic flavorants or natural flavorants , such as lemon , lime , orange , menthol , strawberry , bubblegum , and the like . the optional colorants useful in the present invention , include the pigments such as titanium dioxide , that may be incorporated in amounts of up to about 1 % by weight / volume , and preferably up to about 0 . 6 % by weight / volume . also , the colorants may include other dies suitable for food , drug and cosmetic applications , and known as f . d . & amp ; c . dyes and the like . the materials acceptable for the foregoing spectrum of use are preferably water - soluble . illustrative examples include indigoid die , known as f . d . & amp ; c . blue no . 2 , which is the disodium salt of 5 , 5 ′- indigotindisulfonic acid . similarly , the dye known as f . d . & amp ; c . green no . 1 , comprises a triphenylmethane dye and is the monosodium salt of 4 -[ 4 - nethyl - p - sulfobenzylamino ) diphenylmethylene ]-[ 1 -( n - ethyl - n - p - sulfoniumbenzyl )- 2 , 5 - cyclohexadienimine ]. a full recitation of all f . d . & amp ; c . and d . & amp ; c . and their corresponding chemical structures may be found in the kirk othmer encyclopedia of chemical technology , in volume 5 , at pages 857 - 884 , which text is accordingly incorporated herein by reference . the liquid compositions of the present invention may optionally contain ingredients which improve its taste , such as sodium chloride and natural and artificial flavour enhancers such as monosodium glutamate , soy sauce and the like . the liquid compositions of the present invention contain from about 0 . 5 to 5 % w / v histamine h 2 - antagonist . the histamine h 2 antagonist is selected from the group consisting of nizatidine , famotidine , ranitidine , and cimetidine . the ratio of histamine h 2 - antagonist to alginate is about 1 : 0 . 1 to about 1 : 0 . 6 w / w and preferably about 1 : 02 to about 1 : 04 w / w . alginates are a hydrophilic , colloidal polysaccharide in the form of salts such as sodium , calcium , magnesium and other bases . the preferred form of alginate is an alkali metal salt most preferably the sodium salt . alginate is present in an amount of about 20 % to about 40 % w / w of the histamine h 2 - antagonist . buffers : the buffer comprises acids and their base salts for example , citric acid ( e . g ., citric acid anhydrous ), tartaric acid , malic acid , phosphoric acid and the like and their respective salts . obviously , numerous modifications and variations of the present invention are possible in light of the above teachings and the invention is not limited to the example herein . it is therefore understood that within the scope of the appended claims , the invention may be practiced otherwise than as specifically described herein . in one preferred embodiment of the invention there is provided a composition containing 0 . 5 to 2 . 5 % w / v of histamine h 2 - antagonist . in another preferred embodiment , the histamine h 2 - antagonist is nizatidine . component per 100 ml . % w / v nizatidine 0 . 5 to 2 . 5 humectant 8 to 15 sodium alginate 0 . 1 to 1 . 5 sodium chloride 0 . 1 to 0 . 5 artificial sweetener 0 . 1 to 0 . 5 buffer 0 . 5 to 1 . 5 preservative 0 . 05 to 0 . 5 natural sweetener 20 to 50 flavor 0 . 01 to 1 . 0 artificial sweetness enhancer 0 . 1 to 0 . 9 water to 100 % v / v qs add with mixing the preservative ( s ) to the humectant which is contained in a suitable vessel and has been preheated to about 60 ° c .± 5 ° c . and continue mixing until dissolved . cool the solution to about 50 ° c .± 5 ° c . then slowly add the alginate with continued mixing to uniformly disperse the alginate in the liquid . in a second vessel , add an amount of purified water equal to about 64 % of the final batch volume . add the following ingredients in the order listed below , with continuous mixing and not adding the next ingredient until the current added ingredient is completely dissolved . 3 . buffering agent ( basic portion first if a two component buffer ) stop mixing and pre qs to 95 % of the final batch volume then mix until the solution is uniform . measure the ph ( use temperature compensation to rt ) and adjust the ph if necessary to 6 . 5 . if the ph is greater than 6 . 5 , adjust by adding citric acid solution 20 % and mix well . if the ph is less than 6 . 5 , adjust by adding sodium hydroxide 1n and mix well . discontinue mixing and qs to the final batch volume with purified water .
this invention relates to new pharmaceutical compositions and methods for their preparation , and in particular it relates to taste - masked liquid compositions comprising a solution of a histamine h 2 - antagonist complexed with an alginate and also containing a humectant . the solution is buffered to a ph of between about 6 to 7 . the inventive solution may be flavored and sweetened and preserved .