it has now been surprisingly found that the use of linear copolymer n - vinyl - 2 - pyrrolidone / vinyl acetate as carrier for co - grinding of scarcely water soluble drugs results in improvements of the crystalline structure of said drugs ( reduction of melting enthalpy and / or melting point ), greater increase of solubility and of dissolution speed with respect to , co - grinding times being the same , what can be obtained by using other carriers commonly used for co - grinding , such as for instance linear polyvinylpyrrolidone , reticulated polyvinylpyrrolidone or cyclodextrins . the technical features and the advantages deriving from the use of n - vinyl - 2 - pyrrolidone / vinyl acetate copolymer ( hereinafter referred to as nvp / va for reasons of shortness ) as carrier for co - grinding of scarcely soluble drugs according to the present invention will be evident from the following detailed description . in a preferred embodiment of the present invention the selected active substance and nvp / va carrier , both in powder form , are pre - mixed in a suitable powder mixer . preferably , powder granulometry can vary within a range between 0 . 01 and 1 , 000 microns both for the carrier and for the drug ; for instance it can vary between 0 . 1 and 200 microns . preferably , the mixture comprising the selected active substance and nvp / va carrier is introduced into the grinding chamber of any grinding mill , together with the grinding means . alternatively the mixture comprising the selected active substance and nvp / va carrier can be introduced directly into the grinding mill without pre - mixing . the mill that can be used for co - grinding an active substance with nvp / va carrier comprises a grinding chamber housing grinding means of any kind ( for instance balls or cylinders ). co - grinding comprises for instance a mechanical stirring carried out by rolling , centrifugal rotation or vibration . co - grinding can be carried out at low or high energy for times varying from 0 . 1 to 48 hours ; preferably for times between 0 . 5 and 8 hours . preferably , the weight ratio of nvp / va carrier to active substance can be between 200 : 1 and 1 : 10 ; still more preferably between 100 : 1 and 1 : 5 ; for instance between 10 : 1 and 0 . 5 : 1 . at the end of co - grinding the resulting powder comprising the composite product according to the present invention can be sieved or used directly in the preparation of the pharmaceutical composition in the desired pharmaceutical form , for instance tablet , capsule , packet , powder , pellet , syrup or solution . the pharmaceutical composition comprising the composite product is prepared by means of the technique known to the person skilled in the art and by using excipients and pharmaceutically acceptable additives commonly used for preparing the desired pharmaceutical forms . many different classes of drugs can be usefully worked with the technique of the present invention , from anti - inflammatory agents to analgesics , relaxants , anti - microbic agents , antiseptics , acid pump inhibitors , h 2 antagonists , anti - emetics and anti - nausea , biliary acids , oral hypoglycemizers , diuretics , anti - hypertensives , sulfonamides , ace - inhibitors , hypolipemizers , anti - mycotic agents , antihistamines , hormones , quinolone derivates , antibacterial agents , beta - lactame and fluoroquinolone antibiotics , antiviral agents , anti - neoplastic agents , immuno - modulators and immuno - suppressors , anti - gout agents , anesthetics , analgesics , antipyretics , 5ht 1 agonists , anti - parkinson agents , anti - psychotic agents , tranquillizers , antidepressants , anti - parasitic agents , non - cortisone anti - allergic agents , anti - asthmatic agents , anti - glaucoma agents , inhibitors of carbonic anhydrase , beta - blockers , and others . drugs to which the present invention can be applied , whatever the therapeutic class they belong to , are scarcely water soluble drugs and drugs with low dissolution speed . non - exhaustive examples are paracetamol , nifedipine , piroxicam , ibuprofen , sulindac , diclofenac , alclofenac , ketorolac , indomethacine , naproxen , fenoprofen , flurbiprofen , ketoprofen , cimetidine , ranitidine , mesalazine , ursodeoxycholic acid , mefenamic acid , sinvastatin , megestrol acetate , lorazepam , diazepam , cyclosporin , ubiquinone , tolbutamide , ketanserine , furosemide , nicergoline , losartan , econazole , miconazole , taxol , progesterone , prednisolone , beclometasone , nalidixic acid , finasteride , ciprofloxacine , ofloxacine , lomefloxacine , methotrexate , etoposide , daunorubicine , tamoxifen , allopurinol , clodronic acid , sumatriptan , carbamazepine , clorpromazine , clozapine , sulpiride , buspirone , fluoxetine , citalopram , caffeine , metronidazole , acetazolamide etc . n - 2 - vinyl - pyrrolidone / vinyl acetate copolymer is a flowing powder with a high pharmaceutical workability thanks to the spray - drying process used to obtain it . said spray - drying technique results in spherical particles with a limited and homogenous size distribution . said morphology of the particles positively affects the flow of the powder and its ability to mix with other excipients . another very important property of said copolymer is its low glass transition temperature ( tg ). by mere comparison , tg of nvp / va is of about 106 ° c ., whereas the one of the corresponding linear polymer n - vinylpyrrolidone is of about 160 ° c . glass transition temperature can be defined as the temperature at which a polymer starts to get fluid without being completely melted . the applicant has found it useful to exploit the technical property of tg of nvp / va for preparing pharmaceutical forms for instance as tablets . as a matter of fact , during the compression of the polymeric powders a low glass transition temperature helps the formation of inter - particle bonds thanks to an easier deformation / fluidization of the single particles . the formation of inter - particle bonds enables to obtain a tablet pharmaceutical form having a higher hardness than the one that could be obtained with other traditional excipients by compression , such as for instance lactose or microcrystalline cellulose . said better compression properties of nvp / va copolymer have led the applicant to use successfully said copolymer as carrier for co - grinding of little soluble drugs so as to obtain powders of drug / carrier composite with improved compression properties with respect to commonly used carriers such as linear polymers , for instance polyvinylpyrrolidone , cyclodextrins , reticulated polymers , for instance crospovidone . beyond better compression properties nvp / va copolymer has a lower hygroscopicity with respect to the corresponding linear polymer polyvinylpyrrolidone . this lower hygroscopicity involves a higher stability of the copolymer during its conservation ( preservation of flow and compression properties ) and a lower negative impact on the stability of moisture - degradable drugs mixed or better co - ground with said carrier . now , it has been unexpectedly found that beyond better compression properties of the resulting powders , co - ground products deriving from scarcely soluble drugs and nvp / va have lower melting enthalpies and lower melting temperatures with respect to co - ground products obtained with previously used carriers such as polyvinylpyrrolidone , cyclodextrins , crospovidone . the following examples of co - ground products obtained with nvp / va ( examples 1 - 8 ) are given to a mere illustrative and non - exhaustive purpose for the invention , compared with co - ground products obtained with other commonly used carriers ( examples a - o ). the properties of co - ground products obtained are described in tables 1 - 7 . 1 — 16 . 6 g of nimesulide are mixed with 49 . 8 g of nvp / va for 15 ′. the powder is then poured into the grinding chamber of a low energy vibrational mill . grinding is carried out for 3 hours . 2 — 13 . 3 g of nimesulide are mixed with 53 . 2 g of nvp / va for 15 ′. the powder is then poured into the grinding chamber of a low energy vibrational mill . grinding is carried out for 3 hours . 3 — 16 . 6 g of nimesulide are mixed with 49 . 8 g of nvp / va for 15 ′. the powder is then poured into the grinding chamber of a low energy vibrational mill . grinding is carried out for 2 hours . 4 — 13 . 3 g of nimesulide are mixed with 53 . 2 g of nvp / va for 15 ′. the powder is then poured into the grinding chamber of a low energy vibrational mill . grinding is carried out for 2 hours . 5 — 2 . 5 g of piroxicam are mixed with 12 . 5 g of nvp / va for 15 ′. the powder is then poured into the grinding chamber of a centrifugal mill . grinding is carried out for 4 hours . 6 — 180 . 0 g of nifedipine are mixed with 800 . 0 g of nvp / va for 15 ′. the powder is then poured into the grinding chamber of a high energy vibrational mill . grinding is carried out for 4 hours . 7 — 13 . 3 g of ursodeoxycholic acid ( udca ) are mixed with 53 . 2 g of nvp / va for 15 ′. the powder is then poured into the grinding chamber of a low energy vibrational mill . grinding is carried out for 4 hours . 8 — 11 . 1 g of ursodeoxycholic acid ( udca ) are mixed with 55 . 5 g of nvp / va for 15 ′. the powder is then poured into the grinding chamber of a low energy vibrational mill . grinding is carried out for 4 hours . a — 16 . 6 g of nimesulide are mixed with 49 . 8 g of pvp for 15 ′. the powder is then poured into the grinding chamber of a low energy vibrational mill . grinding is carried out for 3 hours . b — 13 . 3 g of nimesulide are mixed with 53 . 2 g of pvp for 15 ′. the powder is then poured into the grinding chamber of a low energy vibrational mill . grinding is carried out for 3 hours . c — 16 . 6 g of nimesulide are mixed with 49 . 8 g of pvp - cl for 15 ′. the powder is then poured into the grinding chamber of a low energy vibrational mill . grinding is carried out for 3 hours . d — 13 . 3 g of nimesulide are mixed with 53 . 2 g of pvp - cl for 15 ′. the powder is then poured into the grinding chamber of a low energy vibrational mill . grinding is carried out for 3 hours . e — 16 . 6 g of nimesulide are mixed with 49 . 8 g of pvp for 15 ′. the powder is then poured into the grinding chamber of a low energy vibrational mill . grinding is carried out for 2 hours . f — 13 . 3 g of nimesulide are mixed with 53 . 2 g of pvp for 15 ′. the powder is then poured into the grinding chamber of a low energy vibrational mill . grinding is carried out for 2 hours . g — 16 . 6 g of nimesulide are mixed with 49 . 8 g of pvp - cl for 15 ′. the powder is then poured into the grinding chamber of a low energy vibrational mill . grinding is carried out for 2 hours . h — 13 . 3 g of nimesulide are mixed with 53 . 2 g of pvp - cl for 15 ′. the powder is then poured into the grinding chamber of a low energy vibrational mill . grinding goes on for 2 hours . i — 2 . 5 g of piroxicam are mixed with 12 . 5 g of pvp - cl for 15 ′. the powder is then poured into the grinding chamber of a centrifugal mill . grinding is carried out for 4 hours . l — 2 . 5 g of piroxicam are mixed with 12 . 5 g of β - cyclodextrin for 15 ′. the powder is then poured into the grinding chamber of a centrifugal mill . grinding is carried out for 4 hours . m — 180 . 0 g of nifedipine are mixed with 900 . 0 g of pvp for 15 ′. the powder is then poured into the grinding chamber of a high energy vibrational mill . grinding is carried out for 4 hours . n — 13 . 3 g of udca are mixed with 53 . 2 g of β - cyclodextrin for 15 ′. the powder is then poured into the grinding chamber of a low energy vibrational mill . grinding is carried out for 4 hours . o — 11 . 1 g of udca are mixed with 55 . 5 g of β - cyclodextrin for 15 ′. the powder is then poured into the grinding chamber of a low energy vibrational mill . grinding is carried out for 4 hours . table 1 : variation of δh f and of t f of nimesulide complex with different carriers at 40 ° c . and 75 % of relative humidity ( r . h .). table 3 : co - grinding test of piroxicam with various carriers ( weight ratio piroxicam / carrier : 1 / 5 ). table 4 : co - grinding test of nifedipine with various carriers ( weight ratio nifedipine / carrier : 1 / 5 ). table 6 : co - grinding test of udca with various carriers ( weight ratio nimesulide / carrier : 1 / 4 ). percentage release is given . table 7 : dissolution speed of piroxicam co - ground with different carriers ( weight ratio nimesulide / carrier : 1 / 4 ). percentage release is give . powders of co - ground products obtained by using nvp / va carrier have been characterized by : a differential scanning calorimeter perkin elmer , mod . pyris 1 , with nitrogen flow , and a heating speed of 10 ° c ./ min has been used . the method referred to in usp xxi , no . 2 has been used , using sotax apparatus , with thermostatation of dissolution means at 37 ° c ., and a rotation speed of the blades of 100 rpm . the concentration of dissolved drug has been measured by means of a spectrophotometer ( perkin elmer , mod . lambda 25 ). in the case of piroxicam as dissolution mean hcl 0 . 1n , ph 1 . 2 has been used ; in the case of nimesulide phosphate buffer ph 7 . 5 . table 1 contains data referring to melting enthalpy and temperature of co - ground products obtained from nimesulide with the carrier according to the present invention nvp / va and with comparative carriers linear and reticulated pvp , under different conditions and conservation times : it can be observed that nvp / va has a clearly higher ability in de - structuring nimesulide ( lower melting enthalpies and temperatures ) and in keeping said activation under the various conservation conditions . table 2 contains calorimetry data referring to co - ground products obtained from nimesulide with different carriers , with different weight ratios carrier / drug and different co - grinding times : in all cases co - ground products with nvp / va are more de - structured . table 3 contains calorimetry data referring to co - ground products obtained from piroxicam with different carriers ( nvp / va , pvp - cl , beta - cyclodextrin ): also in this case nvp / va carrier gives rise to lower melting enthalpies and temperatures . in table 4 said higher de - structuring ability of nvp / va is shown for co - ground products with nifedipine , whereas table 5 shows data referring to co - ground products obtained from ursodeoxycholic acid , which here again are more activated with nvp / va carrier . unexpectedly again , higher dissolution speeds for co - ground products with nvp / va with respect to commonly used carriers have been found , as shown in table 6 for nimesulide and table 7 for piroxicam . said better dissolution properties are in line with the better properties of chemical - physical activation .
the present invention describes how to obtain composite products comprising an active substance supported by a carrier , in which the carrier is the linear copolymer of n - vinyl - 2 - pyrrolidone with vinyl acetate . the composite products are obtained by co - grinding of the dry mixture of the active substance and of the aforesaid carrier . the composite products thus obtained have better chemical - physical properties and a higher dissolution speed with respect to composite products obtained with the same - co - grinding time with other carriers used in prior techniques . furthermore , the composite products obtained with the technique according to the present invention have the appearance of powders that are easier to work from a pharmaceutical point of view with respect to composite products previously obtained with other carriers .