a tribasic phosphate salt in which the cation is multivalent includes , for example , tribasic calcium phosphate , tribasic magnesium phosphate and tribasic aluminum phosphate . tribasic calcium phosphate is especially preferred . the ratio of tribasic phosphate salt to agent in the pharmaceutical composition is , for example , within the range of 1 : 80 to 50 : 1 by weight , for example 1 : 50 to 50 : 1 by weight , such as 1 : 10 to 10 : 1 by weight , and more particularly 1 : 5 to 10 : 1by weight . preferably the pharmaceutical composition of the invention is formulated into an oral dosage form , such as a tablet . accordingly a further aspect of the invention comprises a pharmaceutical composition comprising the agent , a tribasic phosphate salt in which the cation is multivalent , and one or more fillers , binders , disintegrates or lubricants . a still further aspect of the invention relates to a pharmaceutical composition for oral administration comprising the agent , one or more fillers , one or more binders , one or more disintegrates , one or more lubricants and a tribasic phosphate salt in which the cation is multivalent . suitable fillers include , for example , lactose , sugar , starches , modified starches , mannitol , sorbitol , inorganic salts , cellulose derivatives ( e . g . microcrystalline cellulose , cellulose ), calcium sulfate , xylitol and lactitol . suitable binders include , for example , polyvinylpyrrolidone , lactose , starches , modified starches , sugars , gum acacia , gum tragacanth , guar gum , pectin , wax binders , microcrystalline cellulose , methylcellulose , carboxymethylcellulose , hydroxypropyl methylcellulose , hydroxyethyl cellulose , hydroxypropyl cellulose , copolyvidone , gelatin and sodium alginate . suitable disintegrates include , for example , crosscarmellose sodium , crospovidone , polyvinylpyrrolidone , sodium starch glycollate , corn starch , microcrystalline cellulose , hydroxypropyl methylcellulose and hydroxypropyl cellulose . suitable lubricants include , for example , magnesium stearate , stearic acid , palmitic acid , calcium stearate , talc , carnauba wax , hydrogenated vegetable oils , mineral oil , polyethylene glycols and sodium stearyl fumarate . additional conventional excipients which may be added include preservatives , stabilisers , anti - oxidants , silica flow conditioners , antiadherents or glidants . other suitable fillers , binders , disintegrates , lubricants and additional excipients which may be used are described in handbook of pharmaceutical excipients , 2 nd edition , american pharmaceutical association ; the theory and practice of industrial pharmacy , 2 nd edition , lachman , leon , 1976 ; pharmaceutical dosage forms : tablets volume 1 , 2 nd edition , lieberman , hebert a ., et al , 1989 ; modern pharmaceutics , banker , gilbert and rhodes , christopher t , 1979 ; and remington &# 39 ; s pharmaceutical sciences , 15 th edition , 1975 . typically the agent will be present in an amount within the range of 1 to 50 %, and preferably from 1 to 20 % ( especially 2 to 15 %) by weight of the composition . typically the tribasic phosphate salt , such as tribasic calcium phosphate , will be present in an amount within the range of 1 to 50 %, for example 1 to 25 %, such as 1 to 20 %, and particularly 5 to 18 % by weight . typically one or more fillers will be present in an amount 30 to 90 % by weight . typically one or more binders will be present in an amount 2 to 90 % by weight . typically one or more disintegrates will be present in an amount 2 to 10 %, and especially 4 to 6 % by weight . it will be appreciated that a particular excipient may act as both a binder and a filler , or as a binder , a filler and a disintegrant . typically the combined amount of filler , binder and disintegrant comprises , for example , 70 to 90 % by weight of the composition . typically one or more lubricants will be present in an amount 0 . 5 to 3 %, and especially 1 to 2 % by weight . preferred compositions of the invention include , for example , those comprising the agent , tribasic calcium phosphate and excipients selected from lactose , mannitol , microcrystalline cellulose , povidone , crospovidone , sodium starch glycollate and magnesium stearate . preferred independent compositions of the invention include , for example , compositions comprising the agent , tribasic calcium phosphate , microcrystalline cellulose , lactose , sodium starch glycollate , butylated hydroxytoluene and magnesium stearate ; compositions comprising the agent , povidone , tribasic calcium phosphate , microcrystalline cellulose , mannitol , sodium starch glycollate , butylated hydroxytoluene and magnesium stearate ; compositions comprising the agent , tribasic calcium phosphate , crospovidone , microcrystalline cellulose , lactose and magnesium stearate , and compositions comprising the agent , povidone , tribasic calcium phosphate , microcrystalline cellulose , lactose , sodium starch glycollate , magnesium stearate and butylated hydroxytoluene . where lactose and microcrystalline cellulose are used , these are preferably present in the ratio of about 1 : 1 to 3 : 1 by weight . compositions of the invention which are of particular interest include , for example , the specific embodiments set out hereinafter in the accompanying examples . the pharmaceutical composition of the invention may be prepared , using standard techniques and manufacturing processes generally known in the art , for example by dry blending the components . for example , the agent , the tribasic phosphate salt ( for example tribasic calcium phosphate ), one or more fillers , one or more binders and one or more disintegrates , as well as other additional excipients if desired are blended together . the components of the blend prior to blending , or the blend itself , may be passed through a mesh screen , for example a 400 - 700 um mesh screen . a lubricant , which may also be screened , is then added to the blend and blending continued until a homogeneous mixture is obtained . the mixture is then compressed into tablets . alternatively , a wet granulation technique can be employed . for example , the agent , the tribasic phosphate salt , one or more fillers , one or more binders and a portion of a disintegrant , as well as other additional excipients if desired , are blended together , for example by using a granulator , and the powder blend is granulated with a small volume of purified water . the granulate is dried and passed though a mill . the remainder of the disintegrant and a lubricant are added to the milled granulation and after blending the resultant homogeneous mixture is compressed into tablets . it will be appreciated that modifications of the dry blending and wet granulation techniques , including the order of addition of the components and their screening and blending prior to compression into tablets , may be carried out according to principles well known in the art . a tablet coating may then be applied , for example by spray - coating . with a water - based film coating formulation . the coating may comprise , for example , lactose , hydroxypropyl methylcellulose , triacetin , titanium dioxide and ferric oxides . coating ingredient combinations are commercially available , such as those described in the examples hereinafter . the coating may comprise , for example , 0 . 5 to 10 % by weight of the tablet composition , particularly 1 to 6 %, and preferably 2 to 3 %. coatings containing ferric oxides are especially preferred as they reduce the rate of formation of photodegradation products of the agent . a further aspect of the present invention comprises a method of preparing a stabilised pharmaceutical composition which comprises admixing the agent with a tribasic phosphate salt in which the cation is multivalent . a further aspect of the present invention comprises a method of producing a stabilised pharmaceutical composition which comprises incorporating a tribasic phosphate salt in which the cation is multivalent in a pharmaceutical composition containing the agent . the following pharmaceutical compositions , wherein the agent is the calcium salt of formula i , are intended to illustrate the invention without being limitative in any way . the agent , microcrystalline cellulose , lactose monohydrate , sodium starch glycolate , tribasic calcium phosphate , and butylated hydroxytoluene were blended together for 10 minutes . magnesium stearate was screened through a # 40 mesh ( 425 um ) screen and added to the blend and blending continued for a further three minutes . the resulting homogeneous mixture was compressed into tablets . the tablets were stored at 70 ° c ./ 80 % relative humidity for one week . after one week there was found to be only 0 . 11 % w / w of the oxidation product b2 formed and only 0 . 50 % w / w of the lactone . by comparison a similar formulation in which 20 . 0 mg of tribasic calcium phosphate was replaced by 20 . 0 mg of dibasic calcium phosphate , 0 . 23 % w / w of b2 was formed and 15 . 61 % w / w of the lactone . the agent , povidone , mannitol , microcrystalline cellulose , butylated hydroxytoluene , tribasic calcium phosphate and sodium starch glycollate ( in the amounts given above ) were blended for 5 to 60 minutes . magnesium stearate was screened through a # 40 mesh ( 425 um ) screen and added to the blend and blending continued for a further three minutes . the resulting homogeneous mixture was compressed into tablets . the compressed tablets were coated by spraying with a mixture of hydroxypropyl methylcellulose , polyethylene glycol 400 , titanium dioxide and ferric oxide ( sold as spectrablend by warner - jenkinson ) and water in a coating pan . the weight gain provided by the coating was 1 to 6 % w / w , and preferably 2 to 3 % w / w . the tablets were stored at 70 ° c ./ 80 % relative humidity for one week . after one week here was found to be only 0 . 06 % w / w of the oxidation product b2 formed and only 2 . 22 % w / w of the lactone . the agent and crospovidone were blended together for 5 minutes and the blend then passed through a 400 - 700 um screen . a small portion of the microcrystalline cellulose was passed through the screen afterwards . the screened material was blended with the other ingredients , excluding the lubricant , for 10 minutes . magnesium stearate was passed through a # 40 mesh ( 425 um ) screen and added to the blend and the mixture was blended for a further 3 minutes . the resulting homogeneous mixture was compressed into tablets . the compressed tablets were coated by spraying with a mixture of lactose monohydrate , hydroxypropyl methylcellulose , triacetin and ferric oxide ( sold as opadry ii by colorcon ) and water in a coating pan . the weight gain provided by the coating 1 to 6 % w / w , and preferably 2 to 3 % w / w . the tablets were stored at 70 ° c ./ 80 % relative humidity for one week . after this time only 0 . 19 % w / w of the oxidation product b2 had formed and only 2 . 71 % w / w of the lactone . a portion of the tribasic calcium phosphate and butylated hydroxytoluene were blended for 30 seconds in a bag . the agent , povidone , remainder of the tribasic calcium phosphate , microcrystalline cellulose , lactose monohydrate , tribasic calcium phophate / butylated hydroxytoluene mixture and a portion of the sodium starch glycolate were blended in a granulator for 30 seconds . the powder blend was granulated with purified water for 1 minute at the addition rate of 70 mg / tablet / minute . the granulation is dried in a fluidized bed drier at 50 ° c . until the loss on drying is less than 2 % w / w . the dried granulation is passed through a mill ( e . g . comil ). the milled granulation and the remainder of the sodium starch glycolate was blended for approximately 5 minutes . magnesium stearate was screened through a # 40 mesh ( 425 um ) screen and added to the blend and blending continued for a further three minutes . the resulting homogeneous mixture was compressed into tablets . the tablets were stored at 70 ° c ./ 80 % relative humidity for one week . after this time only 0 . 23 % w / w of the oxidation product b2 had formed and only 0 . 28 % w / w of the lactone . by comparison a similar formulation in which 20 . 0 mg of tribasic calcium phosphate was replaced by 20 . 0 mg of dibasic calcium phosphate , 0 . 19 % w / w of b2 was formed and 28 . 15 % w / w of the lactone .
the invention concerns a pharmaceutical composition comprising the hmg coa reductase inhibitor - 7 -- 6 - isopropyl - 2 - amino ] pyrimidin - 5 - yl ]-- 3 , 5 - dihydroxyhept - 6 - enoic acid or a pharmaceutically acceptable salt thereof as the active ingredient , which remains stable over a prolonged period .