A compound of the formula I ##STR1## wherein R is lower alkyl has been found to have antiepileptic properties and to be useful in the treating of epilepsy in humans and animals. Pharmaceutical compositions and methods of treatment are described herein.

The present invention is concerned with histidylprolineamide derivatives. 
More particularly, the present invention relates to such derivatives which 
have been found to be useful as antiepileptic agents. Intractable epilepsy 
exhibits various serious symptoms. Efforts have been under way for many 
years to develop drugs useful in the treatment of epilepsy. In recent 
years, some antiepileptics such as phenytoin have been developed and used 
to control epileptic fits and seizures. The fit associated with epilepsy 
is inhibited by continued administration of hypnotics such as 
phenobarbital. However, because the cause of epilepsy is not simple and 
well understood, drugs useful for effecting a recovery from epilepsy have 
not as yet been found. 
Inanaga et al (The Kurume Medical J., 28, 201, 1981) reported on the 
effectiveness of TRH (Thyrotropin-Releasing Hormone) on intractable 
epilepsy. Primarily, TRH was considered to be a hormone which controlled 
the release of thyrotropin (TSH) in the mammalian pituitary gland. 
However, according to recent studies, (see Ann. Rev. Pharmacol. Toxicol. 
26, 311-322, 1986) TRH has been found to regulate not only release of TSH 
but to act on various neurones because of its wide distribution in the 
central nervous system. 
Though it has been known that TRH exhibits various useful actions and can 
be effective as an antiepiletic agent, it is also known that TRH is 
metabolized relatively easily in vivo and its penetration and absorption 
into the brain is, therefore, very poor. Moreover, the action of TRH is 
not as potent as initially expected by research workers in the field. 
Thus, there remains a demand for a potent and effective effective 
anti-epileptic activity. 
Moreover, because of the relatively rapid metabolism of TRH, it is not 
suitable for oral administration. When TRH or TRH-related compounds are 
administered systemically, the duration of their effect is short and the 
effective dosage is rather limited. Experiments have shown that there is 
no dose dependency (thus, the effect does not increase in proportion to an 
increase in dose) and consequently, the development of such drugs has not 
shown promise (see Kiyoshi Morimoto, et al:Noo to Shinkei, 35, 501-504, 
1983). 
Histidylprolineamide derivatives including the compounds of the present 
invention are known to have CNS action and to be useful as 
psychostimulants and antidepressants-see DE 2,449,167 and DE 2,615,455 (BE 
853,444), and have been studied because of their prominent pharmacological 
action. Attempts have been made to use them for the treatment of neuronal 
damage after brain injury for example sectional paralysis resulting from 
bone-marrow trauma and central nervous system dysfunctions resulting from 
brain trauma (see Japanese Laid Open Application 61/172828 and DE 
3502-041A). However, no one has as yet studied the compounds of the 
present invention in relation to specified pharmacological action so that 
they can be used as therapeutic substances. 
The present inventors have discovered that histidylprolineamide derivatives 
of the formula I 
##STR2## 
wherein R is lower alkyl exhibit quite excellent antiepilptic action on 
administration to mammalian animals as compared with TRH. Even upon oral 
administration, the compounds of the present invention exhibit marked 
antiepileptic action and this represents a substantial advance in the art. 
The compounds of the present invention have four asymmetric carbon atoms. 
The present invention thus includes all of the optical isomers. 
According to one embodiment of the present invention, R is methyl, ethyl or 
propyl. Representative compounds of the present invention are : 
6-methyl-5-oxo-3-thiomorpholinylcarbonylhistidylprolineamide. 
6-ethyl-5-oxo-3-thiomorpholinylcarbonylhistidylprolineamide. 
6-propyl-5-oxo 3-thiomorpholinylcarbonylhistidylprolineamide. 
The pharmacological activity and toxicity of the compounds of the present 
invention are illustrated in detail below. In the following test, 
(3R,6R)-6-methyl-5-oxo-thiomorpholinycarbonylL-histidyl-L-prolineamide was 
used as the representative compound of the present invention. 
The animals used were Wistar strain male rats (body weight 240-280 g). They 
were anesthetized by the intraperitoneal injection of 40-50 mg/kg of 
sodium pentobarbital. Then the head of the rat was fixed on a stereotaxic 
apparatus, and silver ball electrodes were placed on the surface of the 
motor cortex. Stainless steel bipolar electrodes were implanted into the 
ipsilateral amygdaloid nucleus according to the brain atlas of Konig and 
Klippel (see Robert E. Krieger Publishing Co., Inc., Huntington, N.Y., 
11743, 1970). Leading wires from the electrodes were connected with each 
pin of the small socket and were fixed on the cranium using dental cement. 
The rat was allowed to completely recover from the surgery. Then 
electrical stimulation was started to develop the kindling. 
The electrical stimulation of the amygdaloid nucleus was applied every 24 
hours by delivering rectangular pulses of 1 mesc duration at 60 Hz for 1 
second every day. The initial stimulating current was 200 .mu.A and, 
depending on the degree of the development of kindling, it was increased 
with a 50 .mu.A step. The degree of convulsion was evaluated with the 
scoving system as given below (Table 1) depending upon the epileptic 
behavior (see Classification according to Racine; Racine, et al: Clin. 
Neurophysiol., 32, 281, 1972). Durations of the afterdischarges were 
determined from the chart which records the EEG. Rats in which the 
symptoms of the fifth grade were observed for three consecutive days and 
the duration of the afterdischarges remained constant were used for the 
experiments. 
The compound of the present invention and TRH were administered 
intraperitoneally 15 and 20 minutes respectively before the electrical 
stimulation. When the drugs were repeatedly administered to the same rat, 
at least five days intervals were set. 
TABLE 1 
______________________________________ 
Scoring systems evaluating for Epileptic Behavior 
Score Epileptic Behavior 
______________________________________ 
1 Twitching of the mouth and face 
2 Nodding of head 
3 Clonic spasm of forefoot 
4 Rearing with hindfoot accompanied by clonic 
convulsion 
5 Falling down accompanied by general convulsion 
______________________________________ 
The results are set forth below in Table 2. 
TABLE 2 
______________________________________ 
Duration of 
Average 
Agent Dose Nos of Afterdischarge 
Degree of 
Used (mg/kg) Animals (% Change) 
Epilepsy 
______________________________________ 
Physiological 
-- 6 106.7 .+-. 3.8 
5.0 
Saline 
The Present 
0.01 5 94.1 .+-. 14.7 
5.0 
Invention 
0.03 4 82.6 .+-. 7.8* 
4.0++ 
Compound 0.1 6 78.7 .+-. 16.8 
3.3++ 
TRH 1 4 104.4 .+-. 3.7 
5.0 
3 4 112.7 .+-. 14.0 
5.0 
10 4 100.6 .+-. 10.0 
5.0 
______________________________________ 
*p &lt; 0.05 (ttest) 
++ p &lt; 0.01 (Wilcoxon's rank sum test) 
The compound of the present invention decreased duration of afterdischarge 
at dosages higher than 0.01 mg/kg, in a dose dependent manner. At doses 
higher than 0.03 mg/kg, it decreased epileptic behavior in a dose 
dependent manner. By contrast, in the case of TRH, no inhibitory effects 
on afterdischarge were observed nor were any effects on epileptic behavior 
observed at the dosages administered. From these results, it is apparent 
that the compound of the present invention is effective to treat 
intractable epilepsy including Lennox-Gastaut epilepsy for which TRH is 
said to be somewhat effective. 
The toxicity of the compounds of the present invention was determined in 
the following manner. The representative compound of the present invention 
was administered intravenously and orally to male mice and the toxic 
symptoms were observed for seven days. Following intravenous 
administration of 1000 mg/kg, no deaths were observed in animals receiving 
the compound of the present invention and no toxic symptoms were observed. 
On oral administration, there was neither death nor toxic symptoms 
observed at a dose of 5000 mg/kg. This is clear evidence that the 
compounds of the present invention are safe. 
The compounds of the present invention may be administered per se or may be 
formulated into pharmaceutical compositions containing pharmaceutically 
acceptable nontoxic carriers. 
When the compounds of the present invention are administered to humans and 
animals as a pharmaceutical composition such compositions contain, for 
example, 0.0001% to 1.2% by weight, for compositions in injectable 
administration form. The range for tablets would be 0.0001 to 2% 
preferably, 0.01% to 1.0% for injection and 0.001 to 1.0% for tablets of 
active ingredient in combination with a pharmaceutically acceptable 
carrier. 
The compounds of the present invention may be given orally, parenterally, 
topically (through the skin) or rectally. They are of course administered 
or applied in forms suitable for the particular administration or 
application route. For example, oral administration would be by tablets or 
capsules; parenteral by injection, infusion or inhilation; topical by 
lotion or ointment; and rectal by suppositories. Oral administration forms 
are particularly preferred. 
As to carriers, one or more liquid, solid or semisolid diluent, filler and 
other auxillary agents for pharmaceutical preparations may be used. It is 
desired that the pharmaceutical compositions are administered in unit 
dosage form. 
Oral administration can be effected utilizing solid and liquid dosage unit 
forms such as powders, tablets, capsules, granules, suspensions, syrups 
and the like. 
Powders are prepared by comminuting the compound to a suitably fine size 
and mixing with a similarly comminuted pharmaceutical carrier such as an 
edible carbohydrate as, for example, starch or mannitol. Flavoring, 
preservative, dispersing and coloring agents can also be present. 
Capsules are made by preparing a powder mixture as described above and 
filling formed gelatin sheaths. Glidants and lubricants such as colloidal 
silica, talc, magnesium stearate, calcium stearate or solid polyethylene 
glycol can be added to the powder mixture before the filling operation. A 
disintegrating or solubilizing agent such as carboxymethylcellulose, 
carboxymethylcellulose calcium, substituted hydroxypropyl cellulose, 
agar-agar, calcium carbonate or sodium carbonate can also be added to 
improve the availability of the medicament when the capsule is ingested. 
When the mixture is finely powdered it may be suspended or dispersed in 
plant oil, polyethyleneglycol, glycerol, surface active agents and the 
like and then packed in gelatine sheaths to prepare soft capsules. 
Tablets are formulated, for example, by preparing a powder mixture, 
granulating or slugging, adding a lubricant and disintegrant and 
compressing into tablets. A powder or pulverized mixture is prepared by 
mixing the compound, suitably comminuted, with a diluent or base as 
described above, and optionally, with a binder as carboxymethylcellulose, 
alginates, gelatin, or polyvinylpyrrolidone, polyvinylalcohol and the 
like, a solution retardant such as paraffin, a resorption accelerator such 
as a quarternary salt and/or an absorption agent such as bentonite, kaolin 
or dicalcium phosphate. The powder mixture can be granulated by wetting 
with a binder such as syrup, starch paste, acadia mucilage or solutions of 
cellulosic or polymeric materials and forcing through a screen or sieve. 
As an alternative to granulating, the powder mixture can be run through 
the tablet machine and the resulting imperfectly formed slugs broken into 
granules. The granules can be lubricated to prevent sticking to the tablet 
forming dies by means of the addition of stearic acid, a stearate salt, 
talc or mineral oil. The lubricated mixture is then compressed into 
tablets. The compounds and pharmaceutically acceptable acid addition salts 
of the present invention can also be combined with free flowing inert 
carriers and compressed into tablets directly without going through the 
granulating or slugging steps. A clear or opaque protective coating 
consisting of a sealing coat of shellac, a coating of sugar or polymeric 
material and a polish coating of wax can be provided. Dyestuffs can be 
added to these coatings to distinguish different unit dosages. 
Oral fluids such as solutions, syrups and elixirs can be prepared in dosage 
unit form so that a given quantity contains a predetermined amount of the 
compound. Syrups can be prepared by dissolving the compound in a suitably 
flavored aqueous solution, while elixirs are prepared through the use of a 
nontoxic alcoholic vehicle. Suspensions can be formulated by dispersing 
the compound in a nontoxic vehicle. Solubilizers and emulsifiers such as 
ethoxylated isostearyl alcohols and polyoxyethylene sorbitol esters, 
preservatives, flavor additives such as peppermint oil or saccharin, and 
the like can also be added. 
Where appropriate, dosage unit formulations for oral administration can be 
microencapsulated. The formulation can also be prepared to prolong or 
sustain the release as for example by coating or embedding particulate 
material in polymers, wax or the like. 
Parenteral administration can be effected utilizing liquid dosage unit 
forms such as sterile solutions and suspensions intended for subcutaneous, 
intramuscular or intravenous injection. These are prepared by suspending 
or dissolving a measured amount of the compound in a nontoxic liquid 
vehicle suitable for injection such as aqueous or oleaginous medium and 
sterilizing the suspension or solution. Alternatively, a measured amount 
of the compound is placed in a vial and the vial and its contents are 
sterilized and sealed. An accompanying vial or vehicle can be provided for 
mixing prior to administration. Nontoxic salts and salt solutions can be 
added to render the injection isotonic. Stabilizers, preservatives and 
emulsifiers can also be added. 
Rectal administration can be effected utilizing suppositories in which the 
compound is admixed with low-melting, water-soluble or insoluble solids 
such as polyethyleneglycols, cocoa butter, higher esters such as myristyl 
palmitate, or mixtures thereof. 
Topical application forms are produced according to techniques and 
procedures per se known and include the usual formulating agents and 
additives. 
In determining the dosage for treating epilepsy a number of factors such as 
the age of the patient, body weight, severity of condition, administration 
route and the like must be considered. Generally, about 0.01 to 50 mg/day 
may be administered to adults, preferably 0.1 to 10 mg/day for a human 
adult. In some cases, a lower dose is sufficient and, in some other cases, 
a higher dose or more doses may be necessary. The administration is 
preferably one to several times a day. 
The compounds of the present invention may be administered alone or in 
combination with other drugs such as antacids, anticholinergic agents 
without CNS action, histamine H.sub.2 antagonists and the like.

The following nonlimitative examples illustrate the preparation of 
pharmaceutical compositions according to the present invention. 
EXAMPLE 1 
(3R,6R)-6-methyl-5-oxo-3-thiomorpholinylcarbonyl-L-histidyl-L-prolineamide 
(4 mg), 50 mg of lactose, 22 mg of corn starch, 5.1 mg of crystalline 
cellulose, 3.4 mg of hydroxypropylcellulose and 0.5 mg of magnesium 
stearate were combined into tablets in accordance with conventional 
procedures. 
EXAMPLE 2 
(3R,6R)-6-methyl-5-oxo-3-thiomorpholinylcarbonyl-L-histidyl-L-prolineamide 
(4 mg), 335 mg of lactose, 144.5 mg of corn starch, 1.5 mg of aqueous 
silicon dioxide and 15 mg of hydroxypropylcellulose were granulated and 
combined into one tablets in accordance with conventional procedures.