Abstract:
A restorative neuropharmacological method of treating motor or speech disturbance comprising administration of L- or DL-threo-DOPS or its pharmaceutically acceptable acid-addition-salt to a patient is provided by stimulating the central nervous system so as to enhance intrinsic neuroplasticity and thus increasing functional compensation.

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims priority benefits under 35 U.S. C Section 119 of Japanese Patent application No. 6-177444, filed Jul. 5th, 1994, the entire disclosure of which is incorporated herein by reference. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     This invention relates to a restorative neuropharmacological agent for motor and speech disturbance originating from central nervous system disorders. 
     2. Description of Related Art 
     L-threo-DOPS (Droxidopa) is a central norepinephrine precursor and is known as an active ingredient for norepinephrine activated nerve function improving agents. Clinically, L-threo-DOPS is used to improve impotent feet and orthostatic dizziness in Parkinson&#39;s disease (stage 3 in the degree of severity according to Yahr) and also to improve orthostatic hypotension, syncope and orthostatic dizziness in familial amyloid polyneuropathy or Shy-Drager Syndrome. 
     Conventionally, improvement of motor and speech disturbance originating from central nervous system disorders has been difficult to treat, and the development of a therapeutic agent was generally believed to be impossible. 
     SUMMARY OF THE INVENTION 
     The object of this invention is to provide restoration from motor and speech disturbance originating from central nervous system disorders by stimulating the central nervous system and thus increasing functional compensation based on intrinsic plasticity of the central nervous system, which restoration conventional physical therapy alone cannot provide. 
     In order to achieve the object set forth above, the restorative neurological therapeutic agent for motor and speech disturbance according to this invention contains L-threo-DOPS as an active ingredient. 
     L-threo-DOPS (Droxidopa) is (-)-(2R, 3R)-2-amino-3-hydroxy-3-(3, 4-dihydroxyphenyl) propionic acid (according to the JAN nomenclature) or (-)-threo-3-(3, 4-dihydroxyphenyl) L-serine (according to the INN nomenclature), the structural formula of which is shown below. ##STR1## 
     L-threo-DOPS, whose molecular formula is C 9  H 11  NO 5 , is white or light brown crystals or crystalline powder with no taste or odor. Droxidopa dissolves only slightly in water, and dissolves very little in ether, ethanol and glacial acetic acid. It is difficult to measure a clear melting point or decomposition point for L-threo-DOPS. L-threo-DOPS shows some changes when the temperature is raised to the vicinity of 220° C., starts melting at 225° C., and turns into a black liquid at around 230° C. The pKa of L-threo-DOPS is 7.88, measured by the titration method. DL-threo-DOPS, which contains 50% L-threo-DOPS, can also be used in this invention. Hereafter, L-threo-DOPS and DL-threo-DOPS are generically denoted as &#34;threo-DOPS&#34;. 
     In this invention, threo-DOPS can be used in a pharmaceutically acceptable acid-addition-salt form as well. For example, inorganic acids such as hydrochloric acid, hydrobromic acid and sulfuric acid and organic acids such as fumaric acid, citric acid, tartaric acid and succinic acid can be used to form an acid-addition-salt. 
     Threo-DOPS can be manufactured by conventional methods, such as those described in U.S. Pat. No. 4,562,263 and U.S. Pat. No. 4,480,109. 
     Conventional pharmacological features of threo-DOPS are as follows: (1) it is directly converted to 1-norepinephrine by the action of the aromatic L-amino acid decarboxylase which is widely distributed in a living body, and thus has an effect of replenishing norepinephrine, (2) it passes through the blood-brain barrier into the brain, (3) it specifically recovers norepinephrine activated nerve functions which have decreased in the central and peripheral nervous system, and (4) it shows various actions via the adrenaline receptors in various tissues. The restorative neuropharmacological agent for motor and speech disturbance according to this invention is effective in improving motor paralysis and motor aphasia after stroke due to subarachnoid hemorrhage, brain infarction, brain hemorrhage, etc. or post-traumatic brain injury wherein physical therapy alone cannot provide improvement, and is particularly effective in increasing the recovery rate in acute stroke cases and enhanced recovery in certain chronic stroke cases. Such actions of threo-DOPS have not been brought to light before, and there has been no functional improvement agent which shows such actions. 
     The functional improvement agent which has threo-DOPS as an active ingredient can be in any form including capsules, tablets, confection, pills, parvule, suppository, solution and ampules. The functional improvement agent which has threo-DOPS as an active ingredient can contain fillers, expanders, binders, dissolution retardants, surfactants, adsorbents, lubricants, coloring agents, perfumes, preservatives, etc. Such preparations can be manufactured following a conventional method. This unique functional improvement agent can also contain other pharmaceutically active ingredients as well. A conventional norepinephrine activated nerve function improving agent which has L-threo-DOPS as an active ingredient is commercially available under the name &#34;DOPS&#34; (manufactured and distributed in Japan by Sumitomo Pharmaceuticals Company, Limited). 
     In particular, the restorative neuropharmacological agent for motor and speech disturbance according to this invention should preferably be used together with a peripheral decarboxylase inhibitor such as benserazide (hereafter referred to as &#34;BSZ&#34;) or carbidopa to promote transfer of threo-DOPS into the brain. To use them together, separate preparations of threo-DOPS and of a peripheral decarboxylase inhibitor can be administered either at the same time or at different times, or a mixture of them can be administered. BSZ can be manufactured using a conventional method. 
     For the administration method of the restorative neuropharmacological agent for motor and speech disturbance according to this invention, depending on the form it takes, oral administration, rectal administration, nasal administration, intravenous administration, hypodermic administration, intramuscular administration, etc. are possible, of which oral administration is preferable. 
     The amount of oral administration of the restorative neuropharmacological agent according to this invention is 60-1,200 mg droxidopa for common adults per day, preferably 100-900 mg, and more preferably 100-400 mg. When a peripheral decarboxylase inhibitor is also administered, the amount of the peripheral decarboxylase inhibitor is empirically 1-10% of the amount of droxidopa, preferably 2.5-7.5%, and more preferably about 5%. For example 5% is particularly preferable for BSZ. However, depending on the age, weight, symptoms, and past history etc. of the subject to whom the medication is administered, the amount of administration of droxidopa and the peripheral decarboxylase inhibitor can be changed as appropriate. In clinical examples, administration of droxidopa alone has shown sufficient efficacy. 
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
     Preparations according to this invention are described below by referring to examples, However, this invention is not limited to those examples. 
     EXAMPLE 1 
     Preparing Capsules 
     200 weight parts of droxidopa, 167 weight parts of an excipient and 3 weight parts of a lubricant are homogeneously mixed, and empty capsules are filled with this mixture in such a way that each capsule contains 200 mg of droxidopa. A capsule preparation is thus obtained. 
     EXAMPLE 2 
     Preparing Capsules 
     100 weight parts of droxidopa, 168 weight parts of an excipient and 2 weight parts of a lubricant are homogeneously mixed, and empty capsules are filled with this mixture in such a way that each capsule contains 100 mg of droxidopa. A capsule preparation is thus obtained. 
     The excipient for Examples 1 and 2 described above is chosen from among lactose, white sugar, glucose, D-mannitol, potato starch, corn starch, wheat starch, calcium carbonate, calcium sulfate, anhydrous calcium phosphate, sodium bicarbonate, crystalline cellulose, a mixture of these, etc. The lubricant is chosen from among magnesium stearate, calcium stearate, talc, etc. 
     Clinical testing was conducted to evaluate the effects of the restorative neuropharmacological agent for motor and speech disturbance according to this invention. 
     Clinical subjects for motor disturbance were 2 cases after cerebral aneurysm operations (subarachnoid hemorrhage), 9 cases of brain hemorrhage and 10 cases of brain infarction with chronic apoplectic paralysis, i.e. a total of 21 cases (12 males and 9 females, age 43-83 with an average 61.9±2.5 years). For these clinical subjects, the average time elapsed from the onset had occurred was 100 days. Table 1 shows the 21 clinical subject cases and 6 control cases. 
     
                       TABLE 1______________________________________List of the short term administration testing cases                               ImprovementCase No. Age      Sex     Diagnosis*                               in FMS______________________________________Cases administered L-DOPS 1       43       Female  BH        Improved 2       51       Female  BI        Improved 3       50       Male    BH        Improved 4       57       Female  BI        Improved 5       59       Male    BH        Improved 6       64       Female  BI        No change 7       66       Female  SAH       Improved 8       47       Male    BH        No change 9       51       Male    SAH       Improved10       61       Male    BI        No change11       60       Male    BI        Improved12       62       Female  BH        Improved13       57       Male    BH        No change14       76       Male    BI        Improved15       64       Male    BI        Improved16       64       Female  BH        Improved17       83       Male    BI        Improved18       71       Female  BH        Improved19       73       Male    BI        No change20       75       Male    BI        No change21       52       Female  BH        Improved______________________________________Control cases (not administered L-DOPS)1        46       Male    BH        No change2        62       Male    BI        No change3        71       Female  BH        No change4        70       Male    BI        Improved5        68       Female  BI        No change6        76       Male    BI        No change______________________________________ *BH: Brain hemorrhage BI: Brain infarction SAH: Subarachnoid hemorrhage 
    
     First, the clinical subjects received physical therapy without administration of droxidopa (L-DOPS), and then they were evaluated with FMS (Fugl-Meyer score), 10-meter walking and the Barthel index. The clinical subjects then received administration of 300 mg droxidopa (L-DOPS) per day for 2 days in addition to the physical therapy, and were evaluated with FMS. 10-meter walking and with the Barthel index. 
     As a result, of the 21 cases to whom droxidopa was administered, 15 cases showed improved FMS, i.e. FMS increased by 2.5±0.5, which was higher than zero, 1±0.2, for the control cases. The t-test showed that P was less than 0.005, indicating a significant difference. For this FMS, 10 of the 21 cases showed improvement in upper limb motor function, 6 of the 21 cases showed improvement in lower limb motor function, and 3 of the 21 cases showed improved balance. On the other hand, of the 6 control cases without droxidopa administration, 0 case, 1 case and 0 case, respectively, showed such improvement. 
     All of the 12 cases with central-facial palsy showed improvement. On the other hand, none of 6 control cases showed improvement. 19 cases of the 21 cases showed improvement in the 10-meter walking. Of these, one case showed improvement in the Barthel index, i.e. improvement in ADL (activities of daily living). 
     After 1-2 weeks, droxidopa was administered again for 2 consecutive days to 5 of the 15 cases who had showed improvement in FMS of the 21 cases who had received 2 days of administration, and further improvement was observed for 3 cases. This indicates that more improvement in motor functions can be expected by administering droxidopa over a longer period of time. The administration of droxidopa to the clinical subjects was then halted, but the level of the improvement effect on motor functions was maintained. 
     Based on the above results, low term administration testing was conducted. The clinical subjects were 10 neurological stable cases who had an onset of stroke 2 months to 2 years before the testing, and 200-500 mg/day of droxidopa was administered for 2 weeks to 2 months. As a result, 7 cases showed improvement in the Barthel index, i.e. improvement in ADL (activities of daily living) was observed for 7 cases of the 10 cases. The results were independent of the time elapsed since onset of the illness. Table 2 shows the list of the 10 clinical subject cases. 
     
                                           TABLE 2__________________________________________________________________________List of the long term administration testing cases                   Improvement                         Amount of L-DOPS administeredCase No.Age   Sex Diagnosis   in ADL                         per day × duration__________________________________________________________________________1    43 Female       Brain stem infarction                   Improved                         200 mg × 2W2    51 Female       Subarachnoid hemorrhage                   No change                         200 mg × 2W3    50 Female       Brain hemmorrhage                   Improved                         300 mg × 3W4    57 Male       Subarachnoid hemorrhage +                   No change                         200 mg × 4W       Brain infarction5    59 Female       Brain hemorrhage                   Improved                         200 mg × 2W6    64 Male       Brain hemorrhage                   Improved                         200 mg × 8W7    66 Male       Brain hemorrhage (AVM)                   Improved                         500 mg × 6W8    47 Male       Brain hemorrhage                   Improved                         300 mg × 6W9    51 Male       Brain hemorrhage                   Improved                         200 mg × 2W10   61 Female       Subarachnoid hemorrhage                   No change                         300 mg × 7W__________________________________________________________________________ AVM: Arteriovenous malformation 
    
     The clinical subjects for speech disturbance were 10 cases of Broca aphasia after stroke (3 males and 7 females, age 51-65 with an average of 58.6±1.6 years). 
     First, without administration of droxidopa, the clinical subjects were evaluated with standard aphasia testing (SLAT). After 300 mg of droxidopa was administered to the clinical subjects 3 times a day for 2 days, speech improved. For 8 of the clinical subjects, 100 mg of droxidopa was administered once a day for a subsequent 2 weeks and evaluation was conducted using SLAT. 
     After 2 weeks of droxidopa administration, the average improvement rates based on SLAT were as follows: &#34;hearing&#34; (short sentences, 33%; imperatives, 16%, &#34;reading&#34; (short sentences, 20%; Chinese character words, 10%), &#34;speaking&#34; (names, 27%; actions, 13%), &#34;writing&#34; (Japanese syllabary words, 20%), and &#34;repeating&#34; (10%). 8 of the 10 cases showed improved SLAT results after 2 weeks of administration. That is, one case showed improvement in &#34;hearing&#34;, 3 cases in &#34;reading&#34;, 7 cases in &#34;speaking&#34;, 6 cases in &#34;writing&#34; and 2 cases in &#34;repeating&#34;. This indicates that more improvement in speech disturbance can be expected by administering droxidopa for a long period of time. 
     Administration of droxidopa to these clinical subjects was stopped after 2 weeks. As a result, speech was totally lost in 2 cases. Subsequently, administration of droxidopa was stopped twice and, in one case, speech was totally lost every time administration was stopped and restored when administration was resumed. This indicates that there is a close relationship between speech improvement and administration of droxidopa. No serious side-effect was observed in the clinical subjects. 
     Droxidopa has already been commercially available in Japan, and the following is reported regarding its safety. 
     (A) Acute toxicity (LD50) is shown in Table 3. 
     
                                           TABLE 3__________________________________________________________________________Acute toxicity results (LD50, mg/kg)Administration  Mice, ICR strain          Rats, SD strain                  beagle dogs                          rhesus monkeysvia    Male      Female          Male              Female                  Male                      Female                          Male                              Female__________________________________________________________________________Oral   &gt;10000      &gt;10000          &gt;10000              &gt;10000                  &gt;5000                      &gt;5000                          &gt;5000                              &gt;5000Hypodermic  &gt;10000      &gt;10000              84                  95                  --  --  --  --Intravenous   &gt;100       &gt;100           16-19                  19                  --  --  --  --__________________________________________________________________________ 
    
     As for general symptoms, reduced voluntary motions, deep breathing and bradypnea were observed with mice and rats, but no abnormal symptom was observed with dogs and rhesus monkeys. 
     (B) Subacute toxicity testing 
     60, 300, 1,500 mg/kg/day was orally administered to SD rats, 200, 600, 2,000 mg/kg/day was orally administered to beagle dogs, and 300, 1,000, 3,000 mg/kg/day was orally administered to rhesus monkeys consecutively for 3 months. As a result, for dogs and monkeys, no abnormality was observed in various observations and testing evaluations. For the rats, suppressed voluntary motions, necrosis of kidney uriniferous tubuli, necrosis of cardiac muscles, etc. were observed with 60 mg/kg/day and higher. Suppression of weight increases and such were observed with 300 mg/kg/day and higher. Drooling was observed with 1,500 mg/kg/day. 
     (C) Chronic toxicity testing 
     10, 30, 100, 300 mg/kg/day was orally administered to SD rats, and 125, 500, 2,000 mg/kg/day was orally administered to beagle dogs consecutively for 12 months. As a result, for dogs, no abnormality was observed in various observations and testing evaluations. For the rats, suppression of weight increases, an increase in thymus weight, necrosis of kidney uriniferous tubuli, degeneration of kidney glomeruli, etc. were observed with 30 mg/kg/day and higher, and drooling, myocarditis and calcification of cardiac muscles, etc. were observed with 100 mg/kg/day and higher. 
     (D) Procreation testing 
     (1) Pre-pregnancy and early pregnancy administration testing 
     60, 200, 600 mg/kg/day was orally administered to SD rats (male and female) consecutively. As a result, no influence was observed on the mating rate, conception rate, nidation number, embryo/neonate death, teratogenic actions or fetal development. 
     (2) Organ forming period administration testing 
     60, 200, 600 mg/kg/day was orally administered to SD rats consecutively. As a result, lower body weights of fetuses and an increase in the occurrence of undulating ribs were observed with 200 mg/kg or higher. However, they were within the range in which they can be restored after birth. No other influence was observed. 30, 100, 300 mg/kg/day was orally administered to rabbits consecutively. As a result, no influence on the rabbits was observed. 
     (3) Perinatal and lactation period administration testing 
     60, 200, 600 mg/kg/day was orally administered to SD rats consecutively. As a result, shortening of the pregnancy period was observed with 600 mg/kg, and suppression of neonatal development after birth was observed with 60 mg/kg or higher. No other influence was observed. 
     (E) Antigenicity testing 
     Endodermoreaction, systemic anaphylaxis reaction, PCA reaction and intra-gel sedimentation reaction testing on guinea pigs (Hartley strain, male) yielded negative results. 
     (F) Mutagenicity testing 
     Back mutation testing using microorganisms, chromosome abnormality testing using cultured cells and micronucleus testing on mice were conducted and no mutagenicity was observed. 
     It is understood that although the present invention has been described in detail with respect to preferred embodiments thereof, various other embodiments and variations are possible to those skilled on the art which fall within the scope and spirit of the invention, and such other embodiments and variations are intended to be covered by the following claims.