the inventors of the present invention have surprisingly found that it is possible to achieve metformin and sitagliptin combination composition having desired dissolution profile without using glidant and / or surface active agents , the resulting formulation may also posses enhanced formulation robustness and stability . in particular , the inventors have found that when the composition of metformin and sitagliptin is devised by judicially using pharmaceutical excipients other than glidants and / or surface active agents , the resulting formulation may exhibit bioequivalency to equivalent doses of their single entity formulations and or achieve consistent tablet weight and dose uniformity . the present invention relates to solid oral pharmaceutical composition comprising sitagliptin or a salt thereof , metformin or a salt thereof and one or more pharmaceutically acceptable excipients , wherein the composition is devoid of glidant and / or surface active agents . the term “ compartment ” used herein throughout the specification is used to intend a part of the dosage form comprising one or both of metformin and sitagliptin , and optional other active ingredients , optionally together with pharmaceutical excipients . the part of the dosage form can be in the form of a layer ( formed by coating or compression ), granules , pellets , tablets , or mini - tablets . preferably , the compartments comprise a homogenous mixture of components . in each compartment , at least one type of active ingredient is contained . in one embodiment , at least in one , optionally in two compartments both metformin and sitagliptin are present . the compartments can comprise immediate or extended release compositions . according to the invention , the composition is devoid of glidant and / or surface active agents . preferably , the compartments are provided in the form of a layer . the pharmaceutical dosage form comprising the compartments will then represent a bilayer tablet , a trilayer tablet or a multilayer tablet , preferably bilayer tablet . the term “ tablet ” used throughout the specification refers to and intended to encompass compressed pharmaceutical dosage formulations of all shapes and sizes , whether coated or uncoated . the term “ layer ” used throughout the specification refers to denote a spatial part of the pharmaceutical composition or dosage form other than that formed by applying a coating . the term “ coating ” used throughout the specification refers to a layer which at least partly covers an object and is applied by various coating processes known in the art . the terms “ metformin ” and “ sitagliptin ” used throughout the specifications refers to any pharmaceutically acceptable salts of metformin and sitagliptin . the preferred salt of metformin is metformin hydrochloride . the preferred salt of sitagliptin is sitagliptin phosphate , more preferably its monohydrate . the term “ immediate release ” used throughout the specification refers that within 2 hours , preferably within 1 . 5 hour , more preferably within 1 hour and most preferably within 30 minutes , at least 80 %, preferably at least 85 %, more preferably at least 90 % of the drug being present in the compartment is dissolved or released . the term “ extended release ” used throughout the specification refers that at least 95 % of the drug being present in the component is not dissolved or released , not before 2 hours , preferably not before 3 hours , and more preferably not before 4 hours . a suitable test for determining the dissolution is the test using apparatus 2 according to the us pharmacopoeia 32 - nf 27 , described in general chapter 711 ( dissolution ). conditions chosen for the test were apparatus 2 with 100 rpm in phosphate buffer medium ph 6 . 8 . in another embodiment , the solid oral pharmaceutical composition is in the form of a multilayer tablet , a bilayer tablet or a trilayer tablet . in an embodiment , the first and second compartments employed in the composition of the invention may include polymers and pharmaceutically acceptable excipients to enable formation of a bilayer coated tablet . in another embodiment , the extended release compartment in the composition of the present invention may contain additional anti - diabetic agents other than metformin . the inventors of the present invention have further determined that if the composition of the present invention is formulated without using glidant , particularly in the core of the composition , the composition may achieve consistent tablet weight and dose uniformity . in another embodiment , the extended release compartment of the composition is substantially free of surface active agents . in another embodiment , the solid oral pharmaceutical composition of the invention is substantially free of surface active agents . in another embodiment , the extended release compartment according to present invention does not contain disintegrants and wherein the immediate release compartment contains one or more disintegrants but no rate controlling agent . in another embodiment , the first and third compartment according to the present invention does not comprise any rate controlling agent , in particular not the rate controlling agent that used in the first compartment . suitable rate controlling agents may be selected from the group consisting of hydrophilic agents ( e . g . water - soluble polymers ), lipophilic agents ( water - insoluble polymers ) and inert matrix agents , wherein the hydrophilic agents are selected from the group of pharmaceutical excipients which generate a gel in contact with water , including cellulose derivatives such as hydroxypropyl methyl cellulose , hydroxyethyl cellulose , hydroxypropyl cellulose , methyl cellulose and the like ; noncellulose polysaccharides such as galactomannanes , guar gum , carob gum , gum arabicum , alginates , pectins , and the like ; polyvinylpyrrolidone ; polyvinylacetate polymers and copolymers ; acrylic acid polymers and copolymers , polyethylene oxide and mixtures thereof ; the lipophilic agents are selected from the group consisting of waxes such as white wax , bees wax , carnauba wax and the like ; fatty acids and alcohols such as stearic acid , palmitic acid , lauric acid and the like , and cetyl alcohol , cetostearyl alcohol , stearyl alcohol and the like ; fatty acids esters such as monostearates of propylene glycol and fatty acid esters of sucrose , sucrose distearate and the like ; and glycerides such as mono -, di - or triglycerides , e . g . palmitin , stearin , behenic , laurin , myristin , hydrogenated vegetable , castor , cottonseed oils , glyceril behenate and the like ; ethyl cellulose ; acrylic acid polymers and copolymers ( available commercially under eudragit ® brand ); and mixtures thereof ; and the inert agents are selected from the group consisting of thermoplastic polymers , which are insoluble and indigestible in the gastrointestinal fluids , such as polyvinyl chloride , polyethylene , vinyl acetate / vinyl chloride copolymers , polymethylmethacrylates , polyamides , silicones , ethyl cellulose , polystyrene , and mixtures thereof . the amount of rate controlling agent in the composition ranges from about 10 to about 50 % w / w , preferably from about 15 % to about 45 % by weight of the composition . the oral solid dosage form composition of the present invention further comprises various pharmaceutical excipients suitable for oral administration . such excipients are selected from the group consisting of binding agents , fillers , filler - binders , disintegrants , lubricants , sweeteners , flavourings and colouring agents , preferably the excipients are selected from the group consisting of binding agents , filler - binders , and lubricants . the fillers and / or filler - binder are selected from the group consisting of different grades of starches , such as maize starch , potato starch , rice starch , wheat starch , pregelatinized starch , fully pregelatinized starch , cellulose , such as microcrystalline cellulose or silicified microcrystalline cellulose , mannitol , erythritol , lactose , such as lactose monohydrate and lactose anhydrous , calcium salts , such as calcium hydrogen phosphate dihydrate , anhydrous dibasic calcium phosphate , sorbitol , and xylitol , particularly preferred , the fillers and / or filler - binders are selected from the group consisting of pregelatinized starch , microcrystalline cellulose , lactose monohydrate , and lactose , even further preferred the filler and / or filler - binder is selected from the group consisting of microcrystalline cellulose and anhydrous dibasic calcium phosphate . the lubricants are selected from the group consisting of stearic acid , sodium stearyl fumarate and magnesium stearate , particularly preferred , the lubricant is magnesium stearate . binding agents are selected from the group consisting of polyvinyl pyrrolidone ( povidone ), copolymers of vinylpyrrolidone with other vinylderivatives ( copovidone ), hydroxypropyl methylcellulose , methylcellulose , hydroxypropylcellulose , powdered acacia , gelatin , guar gum , carbomer such as carbopol , polymethacrylates and starch . in an embodiment , the immediate release ( second and / or third ) compartment additionally comprises disintegrants . the solid oral pharmaceutical composition of the present invention can be prepared by methods known to the person skilled in the art . preferably , the components comprising metformin or salts thereof and sitagliptin or salts thereof are formed by dry granulation , wet granulation , slugging or direct compression or by coating process . the compartments then can be processed in different orders and methods known to the person skilled in the art to form a dosage form . in an embodiment , the process of preparing the solid oral pharmaceutical composition of metformin and sitagliptin or salts thereof comprises steps of : ( a ) providing at least one component comprising metformin or a salt thereof , optionally with sitagliptin or a salt thereof ; ( b ) providing at least one component comprising sitagliptin or a salt thereof , optionally with metformin or a salt thereof ; and ( c ) combining the components of step ( a ) and ( b ), wherein the composition is devoid of glidant and / or surface active agents . in a further embodiment , granulation liquids can be added , especially in second compartment , if the composition comprises metformin or pharmaceutically acceptable salts thereof , as also described elsewhere herein . granulation liquid is removed during further processing of the respective compositions , however , some residual water is required in order to render granulate compressible . in another embodiment , the solid oral composition is in the form of a bilayer tablet and comprises a first layer comprising 90 % of metformin or salts thereof exhibiting extended release , a second layer comprising sitagliptin or salts thereof and 5 % metformin or salt thereof exhibiting immediate release and an immediate - release coating over the two layers comprising 5 % of metformin or salts thereof . in a further preferred embodiment , the first layer is devoid of glidant . in a further preferred embodiment , the tablet is devoid of surface active agents . the present invention is further illustrated by the following examples which are provided merely to be exemplary of the invention and do not limit the scope of the invention . certain modifications and equivalents will be apparent to those skilled in the art and are intended to be included within the scope of the present invention . process : first ( extended release granules ) component of metformin hcl was prepared by mixing metformin , microcrystalline cellulose , maize starch , hypromellose 2208 , carbopol with water . the mixture was granulated to form granules . the granules were then lubricated with magnesium stearate . the second component ( immediate release granules ) component of metformin hcl and sitagliptin phosphate was prepared by mixing metformin , sitagliptin , pvp , kollidon va 64 with water . the mixture was granulated to form granules . the granules were then lubricated with magnesium stearate . the first ( extended release granules ) and second components ( immediate release granules ) were then compressed to form a tablet . the tablet was then further coated with a mixture of metformin hcl , opadry white , peg 4000 and water . process : first ( extended release granules ) component of metformin hcl was prepared by mixing metformin , microcrystalline cellulose , maize starch , hypromellose 2208 , carbopol with water . the mixture was granulated to form granules . the granules were then lubricated with talc . the second component ( immediate release granules ) component of metformin hcl and sitagliptin phosphate was prepared by mixing metformin , sitagliptin , pvp , kollidon va 64 with water . the mixture was granulated to form granules . the granules were then lubricated with magnesium stearate . the first ( extended release granules ) and second components ( immediate release granules ) were then compressed to form a tablet . the tablet was then further coated with a mixture of metformin hcl , opadry white , peg 4000 and water . process : first ( extended release granules ) component of metformin hcl was prepared by mixing metformin , microcrystalline cellulose , maize starch , hypromellose 2208 , sodium lauryl sulfate and carbopol with water . the mixture was granulated to form granules . the granules were then lubricated with magnesium stearate . the second component ( immediate release granules ) component of metformin hcl and sitagliptin phosphate was prepared by mixing metformin , sitagliptin , pvp , kollidon va 64 with water . the mixture was granulated to form granules . the granules were then lubricated with magnesium stearate . the first ( extended release granules ) and second components ( immediate release granules ) were then compressed to form a tablet . the tablet was then further coated with a mixture of metformin hcl , opadry white , peg 4000 and water .
the present invention provides solid oral pharmaceutical compositions comprising combination of metformin and sitagliptin or salts thereof . in particular , the present invention relates to a pharmaceutical composition comprising metformin and sitagliptin or salts thereof which is glidant and / or surface active agent . the invention also includes process of preparing such compositions and method of use of such compositions for treating type ii diabetes .