progestins useful in the present method include progesterone , 5 - dehydroprogesterone , 6 - dehydro - retroprogesterone ( dydrogesterone ), allopregnanolone ( allopregnan - 3α , or 3β - ol - 20 - one ), ethynodiol diacetate , hydroxyprogesterone caproate ( pregn - 4 - ene - 3 , 20 - dione , 17 -( 1 - oxohexy ) oxy ); levonorgestrel , norethindrone , norethindrone acetate ( 19 - norpregn - 4 - en - 20 - yn - 3 - one , 17 -( acetyloxy )-,( 17α )-); norethynodrel , norgestrel , pregnenolone , and megestrol acetate . useful progestins also can include allopregnone - 3α or 3β , 20α or 20β - diol ( see merck index , 12th ed ., 266 - 286 ); allopregnane - 3β , 21 - diol - 11 , 20 - dione ; allopregnane - 3β , 17α - diol - 20 - one ; 3 , 20 - allopregnanedione , allopregnane , 3β , 11β , 17α , 20β , 21 - pentol ; allopregnane - 3β , 17α , 20β , 21 - tetrol ; allopregnane - 3α or 3β , 11β , 17α , 21 - tetrol - 20 - one , allopregnane - 3β , 17α , 20α or 20β - triol ; allopregnane - 3β , 17α , 21 - triol - 11 , 20 - dione ; allopregnane - 3β , 11β , 21 - triol - 20 - one ; allopregnane - 3β , 17α , 21 - triol - 20 - one ; allopregnane - 3α or 3β - ol - 20 - one ; pregnanediol ; 3 , 20 - pregnanedione ; pregnan - 3α - ol - 20 - one ; 4 - pregnene - 20 , 21 - diol - 3 , 11 - dione ; 4 - pregnene - 11 β , 17α , 20β , 21 - tetrol - 3 - one ; 4 - pregnene - 17α , 20β , 21 - triol - 3 , 11 - dione ; 4 - pregnene - 17α , 20β , 21 - triol - 3 - one , and pregnenolone methyl ether , as well as derivatives thereof such as esters with non - toxic organic acids such as acetic acid , benzoic acid , maleic acid , malic acid , caproic acid , citric acid and the like . water - soluble or solulizable progestins such as progesterone , are preferred for use in the present method . apart from their use in fertility control , progestins , particularly progesterone ( prog ), exert various actions in the central nervous system ( cns ). prog receptors are widely distributed in the cns , including hypothalamus , preoptic area , midbrain , cortex , amygdala , hippocampus , caudate - putamen and cerebellum ( n . j . maclusky et al ., nature , 274 , 276 ( 1978 )). moreover , in addition to its synthesis in endocrine organs ( ovary , corpus luteum and adrenal gland ), prog is synthesized locally within central and peripheral nervous tissues ( p . robel et al ., neurochem . int ., 7 , 953 ( 1985 ); p . robel et al ., j . steroid biochem ., 27 , 649 ( 1987 ); h . l . koenig et al ., science , 268 , 1500 ( 1995 )). the presence of receptors and sources of prog within the nervous system as well as its modulation of inhibitory and excitatory amino acids suggest a broader role for prog than simply as a gestational hormone . prog and its related metabolites are cns depressants and exert anesthetic , anticonvulsant and anxiolytic actions by modifying the function of gaba and eaa neurotransmitter systems in the cns . see , for example , m . bixo et al ., psychoneuroendo ., 15 , 159 ( 1990 ); s . o . e . landgren et al ., epilepsy res ., 10 , 156 ( 1991 ); m . d . majewska et al ., science , 232 , 1004 ( 1986 ) and b . c . litter et al ., j . nerv . ment . dis ., 159 , 256 ( 1974 ). however , the relationship of these cns activities of progesterone to any beneficial effects of the steroid on ischemic damage is not understood . in cases where progestins are sufficiently basic or acidic to form stable nontoxic acid or base salts , administration of the compounds as salts may be appropriate . examples of pharmaceutically acceptable salts are organic acid addition salts formed with acids which form a physiological acceptable anion , for example , tosylate , methanesulfonate , acetate , citrate , malonate , tartarate , succinate , benzoate , ascorbate , α - ketoglutarate , and α - glycerophosphate . suitable inorganic salts may also be formed , including hydrochloride , sulfate , nitrate , bicarbonate , and carbonate salts . pharmaceutically acceptable salts may be obtained using standard procedures well known in the art , for example by reacting a sufficiently basic compound such as an amine with a suitable acid affording a physiologically acceptable anion . alkali metal ( for example , sodium , potassium or lithium ) or alkaline earth metal ( for example calcium ) salts of carboxylic acids can also be made . the progestins can be formulated as pharmaceutical compositions and administered to a mammalian host , such as a human patient in a variety of unit dosage or sustained release forms adapted to the chosen route of administration , i . e ., orally or parenterally , by intravenous , intrathecal , intramuscular , topical or subcutaneous routes . thus , the progestins may be systemically administered , e . g ., orally , in combination with a pharmaceutically acceptable vehicle or carrier such as an inert diluent or an assimilable edible carrier . they may be enclosed in hard or soft shell gelatin capsules , may be compressed into tablets , encapsulated in liposomes , and / or may be incorporated directly with the food of the patient &# 39 ; s diet . for oral therapeutic administration , the active compound may be combined with one or more excipients and used in the form of ingestible tablets , buccal tablets , troches , capsules , elixirs , suspensions , syrups , wafers , and the like . such compositions and preparations should contain at least 0 . 1 % of active compound . the percentage of the compositions and preparations may , of course , be varied and may conveniently be between about 2 to about 60 % of the weight of a given unit dosage form . the amount of active compound in such therapeutically useful compositions is such that an effective dosage level will be obtained . the tablets , troches , pills , capsules , and the like may also contain the following : binders such as gum tragacanth , acacia , corn starch or gelatin ; excipients such as dicalcium phosphate ; a disintegrating agent such as corn starch , potato starch , alginic acid and the like ; a lubricant such as magnesium stearate ; and a sweetening agent such as sucrose , fructose , lactose or aspartame or a flavoring agent such as peppermint , oil of wintergreen , or cherry flavoring may be added . various other materials may be present as coatings or to otherwise modify the physical form of the solid unit dosage form . for instance , tablets , pills , or capsules may be coated with gelatin , wax , shellac or sugar and the like . a syrup or elixir may contain the active compound , sucrose or fructose as a sweetening agent , methyl and propylparabens as preservatives , a dye and flavoring such as cherry or orange flavor . of course , any material used in preparing any unit dosage form should be pharmaceutically acceptable and substantially non - toxic in the amounts employed . in addition , the active compound may be incorporated into sustained - release preparations and devices , such as patches or implantable depots or pumps . the active compound may also be administered intravenously , intrathecally , intraperitoneally , or by infusion or injection . solutions of the active compound or its salts can be prepared in water dmso or mixtures thereof , optionally mixed with a nontoxic surfactant or alcohol . other lipophilic vehicles can be employed , such as fixed oils , and cyclodextrins can be used to solubilize the progestin in water , if necessary . under ordinary conditions of storage and use , these preparations can contain a preservative to prevent the growth of microorganisms . the pharmaceutical dosage forms suitable for injection , inhalation , insufflation or infusion can include sterile solutions or dispersions or sterile powders comprising one or more progestins which are adapted for the contemporaneous preparation of sterile injectable or infusible solutions or dispersions , optionally encapsulated in liposomes or biodegradable polymeric microparticles or nanoparticles . in all cases , the ultimate dosage form must be sterile , fluid and stable under the conditions of manufacture and storage . the proper fluidity can be maintained , for example , by the formation of liposomes , by the maintenance of the required particle size in the case of dispersions , or by the use of surfactants . the prevention of the action of microorganisms can be brought about by various antibacterial and antifungal agents , for example , parabens , chlorobutanol , phenol , sorbic acid , thimerosal , and the like . in many cases , it will be preferable to include isotonic agents , for example , sugars , buffers or sodium chloride , i . e ., to use physiological salt ( saline ) solutions . prolonged absorption of the injectable compositions can be brought about by the use in the compositions of agents delaying absorption , for example , aluminum monostearate and gelatin . sterile injectable or infusable solutions are prepared by incorporating the active compound in the required amount in the appropriate solvent , such as dmso , or water , including physiological salt solutions , which can comprise agents such as cyclodextrin , to improve dispersion of the lipid soluble steroid in aqueous media , along with various other ingredients enumerated above , as required , followed by sterilization . in the case of sterile powders for the preparation of sterile injectable solutions , the preferred methods of preparation are vacuum drying and the freeze drying techniques , which yield a powder of the active ingredient plus any additional desired ingredient present in the previously sterile - filtered solutions . the principal active ingredient is compounded for convenient and effective administration in effective amounts with a suitable pharmaceutically acceptable carrier in a dosage unit form as hereinbefore disclosed . a unit dosage form , such as a preselected amount of liquid composition , can , for example , contain the principal active compound in amounts ranging from about 5 to about 1000 mg , with from about 250 to about 750 mg being preferred . expressed in proportions , the active compound is generally present in from about 10 to about 750 mg / ml of carrier . liquid formulations of progesterone can comprise about 1 - 100 mg / ml of vehicle . in the case of compositions containing supplementary active ingredients , the dosages are determined by reference to the usual dose and manner of administration of the said ingredients . as used herein with respect to delivery vehicle , the term “ consisting essentially of ” is defined to mean that the vehicle , e . g ., dmso , water intravenous salt solutions or aqueous suspensions containing liposomes , cyclodextrins , creamophor or suspending agents , may contain minor amounts , e . g ., generally less than 1 - 5 wt -% of pharmaceutically acceptable solvents and adjuvants , as discussed hereinbelow . the active ingredients of the therapeutic compositions and the compounds of the present invention can exhibit anti - stroke activity when administered in amounts ranging from about 0 . 1 mg to about 100 mg per kilogram of body weight per day . a preferred dosage regimen for optimum results would be from about 0 . 5 mg to about 50 mg per kilogram of body weight per day , and such dosage units are employed that a total of from about 0 . 25 gram to about 3 . 0 grams of the active compound for a subject of about 70 kg of body weight are administered in a 24 - hour period . this dosage regimen may be adjusted to provide the optimum therapeutic response and is preferably administered one to three times a day in dosages of about 600 mg per administration . for example , several divided doses may be administered daily or the dose may be proportionally reduced as indicated by the exigencies of the therapeutic situation . a decided practical advantage is that the active compound may be administered in a convenient manner such as by the oral , intravenous , intramuscular or subcutaneous routes . useful dosages of the progestin , i . e ., of progesterone , can be determined from their in vitro activity , and in vivo activity in animal models and , to some extent , from the dosages found to exert other pharmacological effects in humans . methods for the extrapolation of effective dosages in mice , and other animals , to humans are known to the art ; for example , see u . s . pat . no . 4 , 938 , 949 . the invention will be further described by reference to the following detailed examples . male wistar rats ( n = 48 ) weighing 270 - 300 g were employed in all experiments . the effect of exogenously administered prog on the male and not the female rat was tested in order to exclude complicating effects on ischemic cell damage of hormonal fluctuations during the estrus cycle . nonfasted animals were anaesthetized with 3 . 5 % halothane , and maintained with 1 . 0 - 2 . 0 % halothane in 70 % n 2 o and 30 % o 2 using a face mask . rectal temperature was maintained at 37 ° c . throughout the surgical procedure using a feedback regulated water heating system . the right femoral artery was cannulated with medical grade silicone tubing ( technical products , inc ., decatur , ga .) for monitoring blood pressure , and for sampling of blood for blood gas measurements ( ph , po 2 , pco 2 ) before and 20 minutes after initial administration of prog or vehicle . middle cerebral artery ( mca ) occlusion ( mcao ) was induced , as previously described by h . chen et al ., j . cereb . blood flow metab ., 12 , 621 ( 1992 ) and j . koizumi et al ., jpn . j . stroke , 8 , 1 ( 1986 ). briefly , the right common carotid artery , external carotid artery ( eca ) and internal carotid artery ( ica ) were exposed . a length of 4 - 0 monofilament nylon suture ( 18 . 5 - 19 . 5 mm ), determined by the animal weight , with its tip rounded by heating near a flame , was advanced from the eca into the lumen of the ica until it blocked the origin of the mca . two hours after mcao , animals were reanaesthetized with halothane and reperfusion was performed by withdrawal of the suture until the tip cleared the lumen of the ica . four randomly assigned populations of animals were tested . group 1 ( n = 12 ): water soluble prog ( prog with balance of 2 - hydroxypropyl - β - cyclodextrin ) ( sigma chemical co ., st louis , mo .) dissolved in saline ( 4 . 0 mg / ml ) was injected intraperitoneally ( 4 . 0 mg / kg ) 30 minutes before mcao . the remaining injections ( all 4 . 0 mg / kg ) were given at 6 and 24 hours after mcao , respectively . group 2 ( n = 12 ): the experimental protocol was identical to that in group 1 , except that prog ( 4 - pregnene - 3 , 20 - dione ) ( sigma chemical co ., st louis , mo .) dissolved in dimethyl sulfoxide ( dmso ; sigma chemical co ., st louis , mo .) ( 8 . 0 mg / ml ), instead of water soluble prog , was administered . group 3 ( n = 12 ): the experimental protocol was identical to that in group 2 , except that the initial injection was delayed to the onset of reperfusion ( 2 hours after mcao ). group 4 ( n = 12 ): the experimental protocol was the same as that in group 2 , except that the same volume of dmso without prog ( 0 . 5 ml / kg ) as in group 2 was administered . in a preliminary pharmacokinetic study ( n = 2 ) using coat - a - count prog procedure kit ( diagnostic products co ., los angeles , calif . ), a solid - phase radioimmunoassay , demonstrated that prog was absorbed rapidly by the intraperitoneal route of administration ; the plasma level of prog increased to 41 . 9 and 70 . 7 ng / ml 4 hours after administration of dmso dissolved prog at the dose of 4 . 0 mg / kg from the pre - injection level of 7 . 17 and 5 . 29 ng / ml , respectively . all animals were weighed before surgery for mcao and at 24 and 48 hours after mcao . neurological abnormalities were also evaluated 24 and 48 hours after mcao using the scale ( 0 - 4 ) described by z . longa et al ., stroke , 20 , 84 ( 1989 ). rats were held gently by the tail , suspended one meter above the floor , and observed for forelimb flexion . normal rats that extend both forelimbs toward the floor and that exhibited no other neurological deficit were assigned grade 0 . rats that consistently flexed the left forelimb ( contralateral to the injured hemisphere ) accompanying flexion of the wrist toward left without any other abnormality were graded 1 . rats that were allowed to move about freely and circled toward the paretic side consistently were graded 2 . rats that fell down to the left losing the ability to walk were graded 3 . rats that exhibited a depressed level of consciousness were graded 4 . forty - eight hours post mcao , the animals were reanaesthetized with ketamine ( 44 mg / kg ) and xylazine ( 13 mg / kg ). transcardiac perfusion with heparinized saline was performed on all animals to remove blood from cerebral vessels . thereafter , the animals were decapitated , and the brains were quickly removed . each brain was cut into 2 - mm thick coronal sections ( 7 sections per brain ) using a rat brain matrix and was then stained for 30 minutes in a 2 % solution of 2 , 3 , 5 - triphenyltetrazolium chloride ( ttc ) at 37 ° c . ttc , a tetrazolium salt , reacts with mitochondrial respiratory enzymes and is reduced to a red formazan - insoluble product by electron acceptance . this reaction is lost in damaged mitochondria or oxidative systems , and the lack of staining demarcates ischemic from normal brain tissue ( j . b . bederson et al ., stroke , 17 , 1304 ( 1986 )). after ttc staining , the tissues were fixed by immersion in 10 % buffered formalin solution . each ttc stained section was photographed with a 35 - mm camera mounted on an operating microscope within 2 days of ttc staining . the unstained area as well as the total right and left hemispheric area for each coronal section were traced using the global lab image analysis system ( data translation , malboro , mass ). the indirect lesion area , in which the intact area of the ipsilateral hemisphere was subtracted from the area of the contralateral hemisphere , was calculated ( r . a . swanson et al ., j . cereb . blood flow metab ., 10 , 290 ( 1990 )). infarct , and left and right hemisphere volumes ( mm 3 ) were determined by multiplying the respective corresponding areas by the section interval thickness . the lesion volume is presented as a volume percentage of lesion compared to the contralateral hemisphere . for parametric variables , a one way anova was applied to determine the statistical significance of differences among groups . if a significant difference was detected , then two sample t - tests with bonferroni correction were performed to evaluate differences between control and prog treated groups . paired t - tests were performed on physiological parameters before and after administration of prog and dmso within each group . values presented in this study are mean ± s . e . m . a probability value less than 0 . 05 was considered significant . the physiological variables before and after initial prog / dmso treatments are shown in table 1 . all values were within the normal range for rats and there was no significant difference in physiological variables before and after injection of either prog or dmso . as shown in table 2 , the percent infarct volume was significantly decreased in both dmso dissolved prog pre - treated ( 39 %, t = 2 . 5616 , p = 0 . 018 ) and delayed treated ( 34 %, t = 2 . 3690 , p = 0 . 027 ) groups compared with the dmso treated control group . the difference of infarct in water soluble prog treated group in relation to the dmso treated control group is not statistically significant ( 18 %, t = 1 . 0833 , p = 0 . 290 ). fig1 shows the distribution of percent area of infarct in each of the seven brain sections from all the four groups . table 3 presents results of body weight loss and the neurological deficit score 24 and 48 hours after onset of ischemia in each group . both groups of regular prog treated animals exhibited a significantly improved physiological response as reflected by a reduced body weight loss and improved neurological function ( lower score ) compared with the dmso group . following the methodology of example 1 , three randomly assigned populations of animals were tested . group 1 ( n = 7 , saline controls ); group 2 ( n = 7 , water - soluble prog dissolved in saline 4 . 0 mg / ml was injected intravenously ( 4 . 0 mg / kg ) two hours after induction of mcao ); group 3 ( n = 7 , prog injected i . v . ( 8 mg / kg ) two hours after induction of mcao ). functional and neurological outcome measures were performed for all experimental groups . these measures included : the accelerating rotarod test , somatosensory tab removal , weight loss and gross neurological examination using the zea longa test described in example 1 . the accelerating rotarod measures the time a rat remains on a rotating treadmill . this is an index of motor function and balance . the rats are trained prior to ischemia to remain on the treadmill and the time on the rotarod is measured for each rat . daily after stroke , the rat is placed on the treadmill and time before fall is measured . the somatosensory measurement involves placement of a round colored paper tab on the forelimb of the rat . prior to ischemia , the rat senses the presence of the tab and removes it within seconds , after ischemia the time of removal is delayed . measurement of the time for removal of the tab provides a sensitive index of somatosensory function . weight loss provides an index of general physiological status . animals with large weight loss have worse strokes and persistent weight loss is an indication of poor recuperation . the gross neurological examination measures limb weakness and circling as an index of stroke deficit as described in example 1 . the rotarod and somatosensory tests are considered the most sensitive tests for neurologic recovery . the main analysis approach measures analysis of variance for the variables which were collected daily for seven days . this analysis gave test results for a time effect , for a treatment group effect and for time by treatment interaction . for lesion size , one way analysis of variance was used for the main testing . correlations between each outcome and lesion volume were computed within each treatment group . plots of the repeated outcomes are given in fig2 - 4 , attached . lesion volume results , measured as described in example 1 , are summarized in fig5 . except for weight ( data not shown ), all of the outcomes show a treatment effect . as shown in fig2 - 5 , the data demonstrated that treatment of the rat with 8 mg / kg of progesterone in saline post mcao , significantly improved neurologic outcome compared with non - treated or treated animals treated with 4 mg / kg of progesterone . the temporal profile of rotarod , somatosensory and gross neurologic function was significantly altered and improved in the 8 mg / kg group and lesion volume was reduced . there was no benefit from the 4 mg / kg dose . these data indicate that progesterone significantly reduces neurological deficits after stroke and is a highly efficacious treatment for stroke in this animal model . although the mechanisms underlying the neuroprotection against cerebral ischemia by prog are unknown , influencing brain excitability may be one of them . potentiating the gaba receptor and / or inhibiting eaa receptors , especially n - methyl - d - aspartate ( nmda ) subtype of the glutamate receptor , can offer protection against ischemic damage . in vivo studies have established that physiological levels of prog enhance gaba - mediated inhibition of neuronal activity ( s . s . smith et al ., prog . neurobiol ., 44 , 55 ( 1994 )). prog rapidly alters the excitability of neurons , in part by potentiating gaba - evoked cl currents and like other gaba potentiating drugs , prog possesses anticonvulsant activity ( t . g . kokate et al ., j . pharmacol . exp . ther ., 270 , 1223 ( 1994 )). circulating prog is a lipophilic compound and easily passes through the blood - brain barrier ( bbb ) and enters the cns at widespread sites . once sequestered within the neuronal population , prog is then metabolized to other more active forms , such as 3α , 5α - thp and the levels of the 3α - hydroxy c21 steroids in cns parallel cyclic fluctuations of prog in the circulation . in conclusion , these examples demonstrate that administration of prog in dmso or saline to the male rat before or after transient mcao reduces ischemic cell damage and improves physiological and neurological function 2 - 7 days after stroke . all patents , patent documents and publications cited hereinabove are incorporated by reference herein . while the invention has been described with reference to certain preferred embodiments , those skilled in the art will realize that changes and modifications may be made thereto without departing from the full and intended scope of the appended claims .
a method for the treatment of ischemic damage , such as damage due to stroke or myocardial infarction , is provided , comprising administering to a mammal afflicted with stroke , an effective amount of a progestin in a suitable vehicle .