suitable stimulant laxatives for use in the compositions produced in accordance with the invention include danthron ( 1 , 8 - dihydroxyanthraquinone ), bisacodyl , casanthranol , cascara , sennosides and sodium picosulphate . of these , danthron is particularly preferred . by the term &# 34 ; normally solid &# 34 ;, as applied to the stool softening agent we mean a material which is solid at ambient temperatures , e . g . 20 ° to 25 ° c . in order to provide the desired melt , in which the stimulant laxative is dispersed , the stool softener suitably has a melting point of from 30 ° to 90 ° c ., preferably 40 ° to 80 ° c . as measured after addition of the stimulant laxative , and any minor additives , which may lower the solidification or melting point . examples of suitable stool softeners include the so - called poloxamers ( polyoxyethylene - polyoxypropylene block copolymers ) especially poloxamer 188 . poloxamer 188 is the preferred stool softening agent for use in accordance with the invention . other pharmaceutically acceptable stool softening laxatives may be suitable for use in accordance with the invention provided their melting point , after incorporation of the stimulant laxative , is from 30 ° to 90 ° c . the weight ratio of stool softener to stimulant laxative will vary depending upon the specific nature of the two components and the desired intended effect . when the stool softener is poloxamer 188 and the stimulant laxative is danthron the weight ratio of stool softener to stimulant laxative is suitably from 2 : 1 to 20 : 1 , preferably from 4 : 1 to 15 : 1 and most preferably from 8 : 1 to 13 . 3 : 1 . the compositions to be filled into the capsules , in accordance with the invention , are simply prepared by melting the stool softener and maintaining its temperature at the desired level , in a jacketed stainless steel mixing vessel . the stimulant laxative is dispersed in the molten stool softener by mixing and homogenization until a uniform dispersion is obtained . the molten dispersion is then filled into gelatin capsules and the capsules cooled . it should be understood that to obtain an unexpectedly high dose in a preparation of small physical size it is particularly advantageous if all or part of the stimulant laxative dissolves in the molten stool softener . for example danthron will dissolve in poloxamer 188 to the extent of approximately 2 % w / w at 60 ° c . and approximately 3 % w / w at 80 ° c . thus for a preparation containing 500 mg of poloxamer 188 and 37 . 5 mg danthron prepared according to the invention , approximately 40 % ( 15 mg ) of the danthron will be dissolved in the poloxamer at 80 ° c . for a preparation containing 200 mg poloxamer 188 and 25 mg of danthron approximately 24 % ( 6 mg ) of the danthron will be dissolved in the poloxamer at 80 ° c . this enables the size of the resulting dosage form to be minimized . in order that the invention may be well understood the following examples and comparative examples are given by way of illustration only . melt the poloxamer 188 in a jacketed stainless steel mixing vessel and maintain the temperature at 60 ° to 80 ° c . add the danthron with vigorous mixing and homogenization and continue mixing and homogenizing until a uniform solution / dispersion is obtained . fill the molten dispersion into size 3 hard gelatin capsules ( volume 0 . 3 ml ) using a capsule filling machine equipped for liquid filling of capsules , for example a bosch 1500l machine . the density of the contents of the capsule shell , prepared according to the present invention , is approximately 0 . 84 g / ml . therefore by preparing capsules according to the invention the normal dose of co - danthramer can be achieved by administering one or two size 3 capsules as the volume of the preparation has been minimized by achieving a high density . it is further surprising that capsules prepared according to the invention and without any excipients to aid manufacture or disintegration exhibit excellent uniformity of danthron content and satisfactory dissolution rate of the danthron as shown below : ______________________________________time during danthron content coefficient ofencapsulation run ( mg / capsule ) variation (%) ______________________________________start 24 . 7 2 . 45middle 24 . 9 1 . 90end 24 . 6 1 . 82______________________________________time ( minutes ) danthron dissolved (%) ______________________________________10 1820 4830 7345 95______________________________________ melt the poloxamer 188 in a jacketed stainless shell mixing vessel and maintain the temperature at 60 ° to 80 ° c . add the danthron with vigorous mixing and homogenization and continue mixing and homogenizing until a uniform solution / dispersion is obtained . fill the molten dispersion into size 0 hard gelatin capsule ( volume 0 . 68 ml ) using a capsule filling machine equipped for liquid filling of capsules , for example a bosch 1500ol machine . the density of the contents of the capsule shell , prepared according to the present invention , is approximately 0 . 98 g / ml . therefore by preparing capsules according to the invention the normal dose of strong co - danthramer can be achieved by administering one or two size 0 capsules as the volume of the preparation has been minimized by achieving a high density . it is further surprising that capsules prepared according to the invention and without any excipients to aid manufacture or disintegration exhibit excellent uniformity of danthron content and satisfactory dissolution rate of the danthron as shown below : ______________________________________time during danthron content coefficient ofencapsulation run ( mg / capsule ) variation (%) ______________________________________start 36 . 9 0 . 96middle 36 . 2 1 . 36end 37 . 2 2 . 25______________________________________time ( minutes ) danthron dissolved (%) ______________________________________10 1420 3830 5945 83______________________________________ blend powdered poloxamer 188 and the danthron in a mixer until a uniform blend is obtained . fill powder into size 1 hard gelatin capsule ( volume 0 . 5 ml ). the density of the contents of the capsule shell , prepared according to the comparative example is approximately 0 . 45 g / ml . therefore by preparing capsules by conventional powder filling the normal dose of co - danthramer can only be achieved by administering one or two size 1 capsules even in the absence of excipients which would be required to enable the powder blend to be filled on a high speed capsule filling machine . blend powdered poloxamer 188 and the danthron in a mixer until a uniform blend is obtained . fill powder blend into size 000 hard gelatin capsule ( volume 1 . 37 ml ). the density of the contents of the capsule shell , prepared according to the comparative example is approximately 0 . 45 g / ml . therefore by preparing capsules by conventional powder filling the normal dose of strong co - danthramer can only be achieved by administering one or two size 000 capsules even in the absence of excipients which would be required to enable the powder blend to be filled on a high speed capsule filling machine . size 000 capsules are generally regarded as too large for human administration , being utilized for large animal veterinary applications and use of smaller size 0 capsules would necessitate administration of two or four capsules to achieve the normal dose of strong co - danthramer . thus it was found that conventional methods of formulation of a stimulant laxative , danthron , and a stool softener , poloxamer 188 yielded an unacceptably large dosage form even before addition of the excipients necessary to allow commercial manufacture . preparation of capsules according to the invention , therefore , allows for the manufacture of a laxative composition in unit dosage form without addition of any excipients or other adjuvant and which furthermore minimizes the volume of the active ingredients to enable achievement of an unexpectedly high dose in a preparation of small physical size .
a method for the manufacture of a laxative composition in dosage unit form which comprises the steps of melting a normally solid stool softener ; dispersing and / or dissolving a stimulant laxative compound in the molten stool softener and mixing to obtain a uniform mixture ; filling the molten dispersion into hard gelatin capsule shells ; and allowing the capsules to cool and the melt or dispersion to solidify .