preferred forms of the present invention will now be described with reference to the accompanying drawings in which : [ 0040 ] fig1 is a plasma oestradiol concentrations following intramuscular injection of 0 . 72 mg ( closed square ) or vaginal administration of 7 . 2 mg ( open square ) of oestradiol 17β . error bars are standard error means ( n = 3 ). [ 0041 ] fig2 is a plasma oestradiol concentrations following vaginal administration of 10 mg oestradiol benzoate ( open square ), 10 mg oestradiol benzoate with 1 : 1 molar ratio β - cyclodextrin ( open diamond ), 10 mg oestradiol benzoate with 1 : 1 molar ratio hydroxypropyl β - cyclodextrin ( open circle ) or 10 mg oestradiol benzoate with 1 : 1 molar ratio γ - cyclodextrin ( open triangle ). error bars are standard error means ( n = 4 ). [ 0042 ] fig3 is a plasma oestradiol concentrations following vaginal administration of oestradiol 17β 7 . 2 mg ( open square ), 7 . 2 mg with 1 : 1 molar ratio β - cyclodextrin ( open diamond ), 7 . 2 mg with 1 : 1 molar ratio hydroxypropyl β - cyclodextrin ( open circle ) or 7 . 2 mg with 1 : 1 molar ratio γ - cyclodextrin ( open triangle ). error bars are standard error means ( n = 4 ). [ 0043 ] fig4 is a plasma oestradiol concentration following vaginal administration of 1 . 2 mg ( closed diamond ), 2 . 5 mg ( closed square ) or 7 . 2 mg ( closed triangle ) oestradiol 17β with 0 . 5 : 1 molar ratio of γ - cyclodextrin to oestradiol 17β . error bars are standard error means ( n = 4 ). [ 0044 ] fig5 is a plasma oestradiol concentration following vaginal administration of 1 . 2 mg ( closed diamond ), 2 . 5 mg ( closed square ) or 7 . 2 mg ( closed triangle ) oestradiol 17β with 1 : 1 molar ratio of γ - cyclodextrin to oestradiol 17β . error bars are standard error means ( n = 4 ). [ 0045 ] fig6 is a plasma oestradiol concentration following vaginal administration of 1 . 2 mg ( closed diamond ), 2 . 5 mg ( closed square ) or 7 . 2 mg ( closed triangle ) oestradiol 17β with 3 : 2 molar ratio of γ - cyclodextrin to oestradiol 17β . error bars are standard error means ( n = 4 ). [ 0046 ] fig7 is a area under the plasma oestradiol concentration against time curve ( auc ) following vaginal administration of 1 . 2 mg , 2 . 5 mg or 7 . 2 mg oestradiol 17β with γ - cyclodextrin to oestradiol 17β molar ratio of 0 . 5 ( closed diamond ), 1 ( closed square ) or 1 . 5 ( closed triangle ). error bars are standard error means ( n = 4 ). [ 0047 ] fig8 is a time to maximum plasma concentration ( tmax ) following vaginal administration of 1 . 2 mg , 2 . 5 mg or 7 . 2 mg oestradiol 17β with γ - cyclodextrin to oestradiol 17β molar ratio of 0 . 5 ( closed diamond ), 1 ( closed square ) or 1 . 5 ( closed triangle ). error bars are standard error means ( n = 4 ). [ 0048 ] fig9 is a maximum plasma oestradiol concentration ( cmax ) following vaginal administration of 1 . 2 mg , 2 . 5 mg or 7 . 2 mg oestradiol 17β with γ - cyclodextrin to oestradiol 17β , molar ratio of 0 . 5 ( closed diamond ), 1 ( closed square ) or 1 . 5 ( closed triangle ). error bars are standard error means ( n = 4 ). [ 0049 ] fig1 is a plasma oestradiol concentration at time = 0 and time = 24 hours post vaginal administration of various doses of oestradiol 17β ( 1 . 2 , 2 . 5 or 7 . 2 mg ) with various rations of γ - cyclodextrin ( 0 . 5 , 1 , 1 . 5 molar ration of γ - cyclodextrin to oestradiol 17β ). error bars are standard error means ( n = 4 ). * denotes a significant difference between the plasma oestradiol concentration at time = 0 and time = 24 hours ( p & lt ; 0 . 050 ). the use of oestradiol 17β and not the synthetic analogue oestradiol benzoate has not been firmly established due to the poor results with vaginally administered oestradiol benzoate and a perception that the shorter acting oestradiol 17β would not be as effications as the longer acting oestradiol benzoate . when oestradiol 17β in a dose equivalent to 1 mg oestradiol benzoate , i . e . 0 . 72 mg , is administered by i . m . injection in cattle the plasma oestradiol concentration rapidly rises to a maximum of approximately 100 pg / ml , followed by a rapid decline to pre injection levels by 24 hours following injection . see fig1 . because of this rapid decline in plasma oestradiol levels an oestradiol 17β dose of 5 mg is commonly used to ensure adequate plasma oestradiol concentrations to achieve the same effect as 1 mg of oestradiol benzoate . we have found that unlike oestradiol benzoate vaginally administration oestradiol 17β is well absorbed , with a dose of 7 . 2 mg achieving a peak plasma concentration of between 10 and 20 pg / ml within four hours following administration , and the plasma oestradiol levels are elevated for at least 24 hours when oestradiol 17β is vaginally administered compared to the more rapidly cleared i . m . injection of oestradiol 17 . we have found that the cyclodextrins improve the vaginal absorption of oestradiol benzoate . we have found that β or γ - cyclodextrin approximately double the plasma oestradiol concentration when vaginally administered with oestradiol benzoate ( 10 mg ) compared with oestradiol benzoate administered without cyclodextrin . see fig2 . furthermore we have found that the cyclodextrin hydroxypropyl β - cyclodextrin elevates plasma oestradiol concentrations approximately 6 fold following vaginal administration with oestradiol benzoate ( 10 mg ) compared with oestradiol benzoate administered without cyclodextrin . we have also found that the cyclodextrins have indeed improved the vaginal absorption of oestradiol 17β . we have found that - cyclodextrin will approximately double the plasma oestradiol concentration when vaginally administered with oestradiol 17β ( 7 . 2 mg ) compared with oestradiol 17β administered without cyclodextrin . see fig3 . furthermore , we have found that the cyclodextrin hydroxypropyl β - cyclodextrin or γ - cyclodextrin elevates plasma oestradiol concentrations approximately 7 to 8 fold following vaginal administration with oestradiol ( 7 . 2 mg ) compared with oestradiol 17β administered without cyclodextrin . we have found that the molar ratio of γ - cyclodextrin to oestradiol 17β influences the vaginal absorption of oestradiol 17β . increasing the ratio of γ - cyclodextrin to oestradiol 17β from 0 . 5 : 1 to 1 : 1 has been found to increase the plasma oestradiol concentration . see fig4 and 6 . further more the effect of the ratio of γ - cyclodextrin to oestradiol 17β upon the vaginal absorption of oestradiol 17β is more pronounced at higher doses (& gt ; 2 . 5 mg ). see fig7 . we have found that vaginal administration of various amounts of oestradiol 17β ( 1 . 2 , 2 . 5 and 7 . 2 mg ) with various molar ratios of γ - cyclodextrin ( 0 . 5 : 1 , 1 : 1 and 3 : 2 ) to oestradiol 17β has no significant effect upon the time to maximum plasma concentration ( tmax ) or the maximum plasma concentration ( cmax ) of oestradiol . see fig8 and 9 . we have found that the vaginal administration of a dose of oestradiol 17β greater than 2 . 5 mg with an amount of γ - cyclodextrin less than or equal to a molar ratio of 1 : 1 ( γ - cyclodextrin to oestradiol 17β ) results in plasma oestradiol concentrations 24 hours post administration significantly greater than those observed prior to administration . see fig1 . we have found vaginal administration of an oestradiol 17β dose of 5 mg and γ - cyclodextrin in a molar ratio of 0 . 5 : 1 ( γ - cyclodextrin to oestradiol 17β ) influences follicular dynamics in a similar manner to those observed following i . m . injection of 2 mg of oestradiol benzoate . see table 1 table 1 tabulates a follicular dynamics and plasma oestradiol pharmacokinetics following vaginal administration of oestradiol 17β 2 . 5 mg or 5 . 0 mg and intramuscular administration of oestradiol benzoate 2 mg .
intra - vaginal delivery procedures including compositions and units therefor whereby an effective releasable amount of oestradiol 17β is released to achieve an efficacious effect insofar as oestrus expression is concerned . preferably a cyclodextrin is utilized to enhance absorption .