the invention will be better understood through the following illustrative and non - limitative description and examples of preferred embodiments of the invention . step 1 : to 1000 g of micronized progesterone were added 280 g of distilled water , with mixing using a planetary mixer , over a period of 30 minutes . after mixing , the wetted micronized progesterone was spread on pans to thickness of about 4 - 5 mm , and the pans then placed in an oven at 58 ° c . the humidity was checked periodically using a humidity checker . when the humidity of the micronized progesterone was reduced to substantially 0 %, the dried micronized progesterone was either used immediately in step 2 as described below , or was stored in dry , sealed containers for later use in step 2 . step 2 : colloidal anhydrous silica ( aerosil 380 , 25 g ) was sieved through a russel sieve having pores of 425 micron size , and mixed for 10 minutes with 1000 g of micronized progesterone from step 1 and 2100 g of maize 1500 starch , using an angelsman mixer at 32 rpm , to form mixture a . at the end of the 10 minutes of mixing , 490 g of povidone 30 were added to mixture a , and mixing was continued for another ten minutes , to prepare “ mixture b ”. step 3 : lactose ( ludipress , basf , 3800 g ), adipic acid ( 570 g ) and sodium bicarbonate ( 430 g ) were mixed for 10 minutes at room temperature using an angelsman mixer at 32 rpm . following mixing , these ingredients were sieved through a russel sieve having pores of 425 microns to obtain “ mixture c ”. step 4 : mixtures b and c were mixed for 10 minutes at room temperature using an angelsman mixer at 32 rpm to obtain “ mixture d ”. step 5 : mixture d ( 8415 g ) was mixed with 3800 g of lactose ( ludipress ) for 10 minutes at room temperature using an angelsman mixer at 32 rpm , to obtain “ mixture e ”. step 6 : magnesium stearate ( 230 g ) and sodium lauryl sulfate ( 50 g ) were sieved through a russel sieve ( pore size 125 microns ). the sieved magnesium stearate and sodium lauryl sulfate were then mixed for with mixture e for 20 minutes at room temperature using an angelsman mixer , to obtain “ mixture f ”. step 7 : tablets were obtained from mixture f by direct compaction using an eko korsch press . the amounts of ingredients listed in this example are suitable for production of 10 , 000 tablets each containing about 100 mg progesterone . using the above process , tablets of 1187 mg to 1312 mg total weight , containing from 90 to 110 mg progesterone , were obtained . the process described in example 1 was modified by doubling the amount of filler ( ludipress ) to obtain tablets containing on average 50 mg progesterone . the pharmacokinetics and clinical use of tablets prepared in accordance with the invention were evaluated as follows : 50 healthy , post - menopausal women with intact uteri , 39 of whom had suffered premature menopause and 11 who were truly postmenopausal , all of whom were undergoing hormone replacement therapy ( hrt ), submitted blood samples for determination of baseline profiles of hormones ( progesterone and other hormones ) and other biochemicals ( bilirubin , cholesterol , etc .). the blood samples were taken at 8 am on the first day of the evaluation ( day 0 ) in a fasting state , by intravenous indwelling catheter which was introduced into the cubital vein . non - estrogen primed postmenopausal women were chosen in order to avoid confusion with endogenous progesterone secretion and estrogen influence on vaginal mucosa absorption ( villanueva et al ., fertil . steril . 35 ( 1981 ), 433 - 437 ). the women then self - administered the progesterone vaginal tablet using a plastic applicator and lay down for 20 minutes . repeat blood samples for progesterone concentration were withdrawn 0 . 5 , 1 , 2 , 4 , 6 , 8 , 10 , 12 and 24 hours after the vaginal insertion . blood was allowed to clot at room temperature for 1 hour , after which the serum was separated by centrifugation and stored at − 20 ° c . until analysis . to evaluate clinical use of the drug , the women were instructed to insert tablets prepared in accordance with the present invention , containing the same dose as administered on day 0 , twice daily starting on day 1 , and to recline for 20 minutes after each insertion . on days 14 and 30 , blood samples for comparison with the baseline were drawn in the morning while the subjects were in a fasting state . of the 50 women who participated in the evaluation , 20 were allocated tablets containing 50 mg progesterone , and the remainder of the participants received tablets containing 100 mg progesterone . the baseline details of the participants are summarized in table i . data are expressed as mean ± standard deviation unless otherwise specified . body mass index ( bmi ) was calculated as weight in kg divided by the square of height in meters . a single vaginal application of a 50 mg progesterone - containing tablet prepared in accordance with the invention resulted in the rapid increase of plasma progesterone concentration . the mean peak plasma level ( t max ), mean elimination half - life ( t 1 / 2 ), maximal serum concentration ( c max ), and auc ( area under the curve , i . e . total amount of plasma progesterone observed ) derived from the blood samples taken on day 0 of the evaluation are summarized in table ii . values are mean ± standard deviation ; a p = 0 . 0004 ; b p = 0 . 001 . as shown in table iii , after 14 and 30 days of continuous application twice daily , the serum p levels were significantly higher compared to baseline values on day 0 . no statistically significant difference in plasma levels of follicle stimulating hormone , leutinizing hormone , estradiol , cortisol , dehydroepiendosterone sulfate , or aldosterone were observed in the study groups between baseline values and after continued administration of the tablets of the invention . similarly , the plasma levels of serum glutamic oxaloacetic transaminase , alkaline phosphatase , cholesterol , triglycerides , high density lipoprotein , low density lipoprotein , and very low density lipoprotein did not change significantly between the baseline measurement and the measurements at 14 and 30 days of twice - daily administration . a p = 0 . 0001 , significant difference between progesterone baseline values on day 0 compared to day 14 and day 30 ; the efficacy of tablets prepared in accordance with the present invention was compared with the efficacy of prior art tablets as follows : thirteen healthy , postmenopausal women with intact uteri who were undergoing hormonal replacement therapy ( hrt ) were given complete medical evaluation by history , physical and gynecological examination , and instructed to discontinue hrt two weeks prior to the comparative trial . part a : single - dose pharmacokinetics of micronized progesterone in the form of a gelatin capsule ( utrogestan , produced by basins - iscovesco , paris , france ). participants received oral ethinyl estradiol ( estrofem , novo - nordisk , denmark ), 4 mg per day for 14 days . on day 14 at 8 am , in a fasting state , an intravenous indwelling catheter was inserted into the cubital vein and blood was drawn for baseline progesterone and estrogen levels . the women were then instructed to self - administer a single gelatin capsule containing 100 mg of micronized progesterone high in the vagina . repeat blood samples for progesterone concentrations were drawn ½ , 1 , 2 , 4 , 6 , 8 , 10 , 12 and 24 hours after the vaginal insertion . part b : single - dose pharmacokinetics of micronized progesterone in the form of a vaginal tablet according to the present invention . after a washout period of 2 weeks , the same subjects as in part a were again administered 4 mg or ethinyl estradiol ( estrofem ) for 14 days . on day 14 the same procedure as recited in part a was repeated , except that this time the women were instructed to insert 100 mg of progesterone in the form of an effervescent tablet according to the present invention , using a plastic applicator . blood samples for progesterone levels were drawn at the same intervals as in part a . samples were assayed using an immulite enzyme immunoassay ( diagnostic products corporation , los angeles , calif .) to measure plasma progesterone ( si conversion factor 3 . 18 ; sensitivity 0 . 2 ng / ml ( 0 . 6 nmol / l , inter - and intra - assay coefficients of variation precision & lt ; 10 %)) and estradiol ( e 2 ) ( si conversion factor 3 . 67 ; sensitivity 12 pg / ml ( 44 pmol / l , inter - and intra - assay coefficients of variation precision & lt ; 10 %). the pharmacokinetic parameters calculated from the concentration curve were compared between the two study groups by the wilcoxon 2 - sample test , the kruskal - wallis test and by analysis of variance ( anova ). students t - test was used to compare estrogen levels for the two treatment parts . table iv summarizes the baseline details of the of the thirteen women who participated in the study of example 5 . data are expressed as mean ± standard deviation unless otherwise specified . body mass index ( bmi ) was calculated as weight in kg divided by the square of height in meters . the mean peak plasma level ( t max ), mean elimination half - life ( t 1 / 2 ), maximal serum concentration ( c max ), and auc ( area under the curve , i . e . total amount of plasma progesterone observed ) derived from the blood samples taken on day 0 of the evaluation are summarized in table v . table v treatment vaginal tablet gelatin capsule tmax ( hours ) 6 . 92 ± 3 . 12 6 . 23 ± 6 . 56 b t 1 / 2 ( hours ) 16 . 39 ± 5 . 25 22 . 08 ± 16 . 5 c max ( nmol / l ) 31 . 53 ± 9 . 15 23 . 85 ± 9 . 57 a auc ( nmol / h / l ) 379 . 99 ± 137 . 07 325 . 89 ± 167 . 78 values are mean ± standard deviation ; a p = 0 . 0472 ; b statistically significant difference of variance , p = 0 . 02 . a single dose of 100 mg micronized progesterone in the form of both gelatin capsules and vaginally administrable tablets in accordance with the present invention resulted in a similar rapid increase in plasma progesterone levels within 2 . 5 - 3 hours after administration . the statistically significant difference of variance between the two groups indicates a more predictable t max for the tablets of the present invention than for the prior art gelatin capsules . it is to be understood that the amounts and proportions of ingredients recited in the foregoing examples are illustrative only , and that these amounts and proportions may be varied within the scope of the invention . for example , the example 1 the amount of effervescent recited is about 8 wt . % of the tablets which are the final product of the process described in example 1 . however , the effervescent may be omitted in the practice of the invention , or it may be included in an amount of up to about 12 wt . % of the tablet . preferably the effervescent constitutes between about 5 - 12 wt . %, more preferably between about 6 - 8 wt . % of the tablet . similarly , progesterone may constitute up to about 20 wt . % of the tablet , preferably between about 6 - 20 wt . %, more preferably between about 8 - 12 wt . % of the tablet . it will be appreciated that various features of the invention which are , for clarity , described in the contexts of separate embodiments may also be provided in combination in a single embodiment . conversely , various features of the invention which are , for brevity , described in the context of a single embodiment may also be provided separately or in any suitable subcombination . it will also be appreciated by persons skilled in the art that the present invention is not limited by what has been particularly shown and described hereinabove . rather the scope of the invention is defined only by the claims which follow :
the present invention provides a method for preparing a tablet for the vaginal administration of progesterone for systemic use . the method comprises first mixing water with micronized progesterone , the total amount of water mixed with said micronized progesterone not exceeding the maximum wetting capacity of the micronized progesterone , drying the wetted , micronized progesterone ; mixing the dry micronized progesterone with other pharmaceutically acceptable excipients or diluents ; and ; forming a tablet by direct compaction of the dry micronized progesterone . tablets prepared by this method are also provided .