the present invention is predicated , in part , on the observation that muscle cramps in a subject can be alleviated by the oral administration of a composition comprising an inhibitory neurotransmitter amino acid . accordingly , one aspect of the present invention contemplates a method for the treatment and / or prophylaxis of muscle cramps and / or muscle stiffness in a mammal comprising administering to said mammal an effective amount of an inhibitory neurotransmitter amino acid and / or a precursor thereof , or a functional derivative , chemical equivalent , mimetic , analogue or homologue thereof for a time and under conditions sufficient to reduce , inhibit or otherwise down - regulate the duration , severity and / or frequency of muscle cramp and / or muscle stiffness . more particularly , the present invention contemplates a method for the treatment and / or prophylaxis of skeletal muscle cramps and / or skeletal muscle stiffness in a mammal comprising administering to said mammal an effective amount of an inhibitory neurotransmitter amino acid and / or a precursor thereof , or a functional derivative , chemical equivalent , mimetic , analogue or homologue thereof for a time and under conditions sufficient to reduce , inhibit or otherwise down - regulate the duration , severity and / or frequency of skeletal muscle cramp and / or skeletal muscle stiffness . reference herein to an “ neurotransmitter ” is to be understood as a reference to a molecule which directly or indirectly modulates the permeability of an ion channel affecting the membrane potential of a muscle cell . reference herein to an “ inhibitory neurotransmitter ” means a molecule which directly or indirectly reduces the likelihood that a muscle cell will generate an action potential . accordingly , the term encompasses “ neuromodulators ” as well as direct “ neurotransmitters ” of synaptic activity . appropriate neurotransmitter agonists or antagonists or neurotransmitter receptor agonists and antagonists are also within the scope of the present invention and within the scope of the term “ inhibitory neurotransmitter ” used herein . examples of neurotransmitters are acetylcholine , histamine , endorphin , gaba ( g - aminobutyric acid ) and glycine . the neurotransmitter of the present invention may be administered as an active or as an inactive precursor molecule . threonine , which may be converted into glycine in vivo , is a particularly contemplated example of a precursor molecule . reference herein to “ an inhibitory neurotransmitter amino acid ” should be understood as a reference to an amino acid which functions as an inhibitory neurotranmitter . reference herein to “ functional derivative , chemical equivalent , mimetic , analogue or homologue thereof ” of an amino acid inhibitory neurotransmitter or of glycine or threonine should be understood to include reference to molecules from natural , synthetic or recombinant sources exhibiting at least one of the functional activities of an inhibitory neurotransmitter amino acid or of glycine or threonine and may be , for example , molecules obtained following natural - product screening . derivatives include those made by chemical modification by addition or removal of one or more moieties . even still more particularly , the present invention contemplates a method for the treatment and / or prophylaxis of skeletal muscle cramps and / or skeletal muscle stiffness in a mammal comprising administering to said mammal an effective amount of glycine and / or a precursor thereof such as threonine , or a functional derivative , chemical equivalent , mimetic , analogue or homologue thereof for a time and under conditions sufficient to reduce , inhibit or otherwise down - regulate the duration , severity and / or frequency of skeletal muscle cramp and / or skeletal muscle stiffness . even more particularly , the present invention contemplates a method for the treatment and / or prophylaxis of skeletal muscle cramps and / or skeletal muscle stiffness in a mammal comprising administering to said mammal an effective amount of glycine and / or a precursor thereof such as threonine , or a functional derivative , chemical equivalent , mimetic , analogue or homologue thereof for a time and under conditions sufficient to reduce , inhibit or otherwise down - regulate the duration , severity and / or frequency of skeletal muscle cramp and / or skeletal muscle stiffness . even still more particularly , the present invention contemplates a method for the treatment and / or prophylaxis of skeletal muscle cramps and / or skeletal muscle stiffness in a mammal comprising administering to said mammal an effective amount of glycine and / or threonine , or a functional derivative , chemical equivalent , mimetic , analogue or homologue thereof for a time and under conditions sufficient to reduce , inhibit or otherwise down - regulate the duration , severity and / or frequency of skeletal muscle cramp and / or skeletal muscle stiffness . in a particular embodiment of this aspect of the present invention , both glycine and threonine are administered . without limiting the present invention to any one theory or mode of action , it is thought that glycine enhances the ability of muscle cells to inhibit efferent alpha - motor neurone activity . furthermore , it is thought that threonine crosses the blood brain barrier where it is converted to glycine to permit the inhibitory neurotransmitter activity of glycine within the central nervous system . reference herein to the treatment and / or prophylaxis of “ muscle cramp and / or stiffness ” should be understood as a reference to the symptoms of involuntary muscle contraction which are associated with a very wide range of conditions found in mammalian subjects . for example , muscle cramps and / or stiffness is found in exercise - induced muscle - fatigued subjects as well as in subjects suffering from inherited or acquired neurological , neuromuscular or muscular disorders or ataxia &# 39 ; s , spasticity , dystonia ; occupational , nocturnal or writers cramp . reference herein to “ treatment ” and “ prophylaxis ” is used in its broadest sense . the term “ treatment ” does not mean that muscle cramps or stiffness is totally cured . similarly , “ prophylaxis ” does not mean that the subject will never develop cramps or muscle stiffness . accordingly , these terms include amelioration of the condition including a reduced duration , severity , or frequency of muscle cramps or muscle stiffness . the subject of treatment and / or prophylaxis herein is generally a mammal such as for example a human , primate , livestock animal ( eg sheep , pig , cow , horse , donkey ) companion animal ( eg cat , dog ) laboratory test animal ( eg mouse , rabbit , rat , guinea pig , hamster ) captive wild animal ( eg fox , deer ). preferably , the mammal is a human or primate . most preferably , the mammal is a human . another aspect of the present invention provides a composition comprising an inhibitory neurotransmitter amino acid and / or a precursor thereof , or a functional derivative , chemical equivalent , mimetic , analogue or homologue thereof for use in the treatment and / or prophylaxis of muscle cramp and / or muscle stiffness in a mammalian subject . another related aspect of the present invention provides a composition comprising an inhibitory neurotransmitter amino acid and / or a precursor thereof , or a functional derivative , chemical equivalent , mimetic , analogue or homologue thereof for use in the treatment and / or prophylaxis of skeletal muscle cramp and / or skeletal muscle stiffness in a mammalian subject . still another aspect of the present invention contemplates a composition comprising glycine and / or a precursor thereof such as threonine , or a functional derivative , chemical equivalent , mimetic , analogue or homologue thereof for use in the treatment and / or prophylaxis of muscle cramp and / or muscle stiffness in a mammalian subject . still yet another aspect of the present invention contemplates a composition comprising glycine and / or a precursor thereof such as threonine , or a functional derivative , chemical equivalent , mimetic , analogue or homologue thereof when used in the treatment and / or prophylaxis of muscle cramp and / or muscle stiffness in a mammalian subject . another aspect of the present invention contemplates a composition comprising glycine and / or threonine , or a functional derivative , chemical equivalent , mimetic , analogue or homologue thereof for use in the treatment and / or prophylaxis of skeletal muscle cramp and / or skeletal muscle stiffness in a mammalian subject . administration of the composition of the present invention may be by any convenient route . oral administration is generally preferred , although pharmaceutical forms of the present composition may be suitable for injectable use such as sterile aqueous solutions ( where water soluble ) and sterile powders for the extemporaneous preparation of sterile injectable solutions or dispersions . the composition must be stable under the conditions of manufacture and storage and must be preserved against the contaminating action of microorganisms such as bacteria and fungi . the carrier can be a solvent or dispersion medium containing , for example , water , ethanol , polyol ( for example , glycerol , propylene glycol and liquid polyethylene glycol , and the like ), suitable mixtures thereof and vegetable oils . the proper fluidity can be maintained , for example , by the use of a coating such as lecithin . 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 or sodium chloride . 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 solutions are prepared by incorporating the active compounds in the required amount in the appropriate solvent with various of the other ingredients enumerated above , as required , followed by filtered 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 technique which yield a powder of the active ingredient plus any additional desired ingredient from previously sterile - filtered solution thereof . the compositions may be orally administered , for example , with an inert diluent or with an assimilable edible carrier , or it may be enclosed in hard or soft shell gelatin capsule , or it may be compressed into tablets , or it may be in powdered form or incorporated directly with the food of the diet . for oral therapeutic and / or prophylactic administration , the active compound may be incorporated with 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 1 % by weight of active compound . the percentage of the compositions and preparations may , of course , be varied and may conveniently be between about 5 to about 80 % of the weight of the unit . the amount of active compound in such therapeutically useful compositions in such that a suitable dosage will be obtained . preferred compositions or preparations according to the present invention are prepared so that an oral dosage unit form contains between about 0 . 01 μg and about 2000 mg of active compound . alternative amounts include between about 1 . 0 μg and about 1500 μg , between about 1 μg and about 1000 mg and between about 10 μg and about 500 mg . the tablets , troches , pills , capsules and the like may also contain the components as listed hereafter : a binder such as gum , 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 a sucrose , lactose or saccharin may be added or a flavouring agent such as peppermint , oil of wintergreen , or cherry flavouring . when the dosage unit form is a capsule , it may contain , in addition to materials of the above type , a liquid carrier . various other materials may be present as coatings or to otherwise modify the physical form of the dosage unit . for instance , tablets , pills , or capsules may be coated with shellac , sugar or both . a syrup or elixir may contain the active compound , sucrose as a sweetening agent , methyl and propylparabens as preservatives , a dye and flavouring such as cherry or orange flavour . of course , any material used in preparing any dosage unit form should be pharmaceutically pure and substantially non - toxic in the amounts employed . in addition , the active compound ( s ) may be incorporated into sustained - release preparations and formulations . pharmaceutically acceptable carriers and / or diluents include any and all solvents , dispersion media , coatings , antibacterial and antifungal agents , isotonic and absorption delaying agents and the like . the use of such media and agents for pharmaceutical active substances is well known in the art . except insofar as any conventional media or agent is incompatible with the active ingredient , use thereof in the therapeutic compositions is contemplated . supplementary active ingredients can also be incorporated into the compositions . it is especially advantageous to formulate parenteral compositions in dosage unit form for ease of administration and uniformity of dosage . dosage unit form as used herein refers to physically discrete units suited as unitary dosages for the mammalian subjects to be treated ; each unit containing a predetermined quantity of active material calculated to produce the desired therapeutic effect in association with the required pharmaceutical carrier . the specification for the novel dosage unit forms of the invention are dictated by and directly dependent on ( a ) the unique characteristics of the active material and the particular therapeutic effect to be achieved , and ( b ) the limitations inherent in the art of compounding such an active material for the treatment of particular conditions in living subjects . the principal active ingredient or ingredients are compounded for convenient and effective administration in effective amounts with a suitable pharmaceutically acceptable carrier in dosage unit form . a unit dosage form can , for example , contain the principal active compounds in amounts ranging from 0 . 01 μg to about 70 g / 100 grams . expressed in proportions , the active compound is generally present in from about 0 . 5 μg to about 2000 mg / ml of carrier . 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 . alternatively , amounts administered may be represented in terms of amounts / kg body weight . in this case , amounts range from about 0 . 001 μg to about 1000 mg / kg body weight may be administered . preferred ranges include from about 50 μg to 500 mg 1 kg body weight 500 mg / kg body weight or about 0 . 01 μg to about or above 0 . 1 μg to about 250 mg / kg body weight are contemplated by the present invention . for use in the treatment and / or prophylaxis of muscle cramp and / or muscle stiffness in a mammalian subject . even yet another related aspect of the present invention contemplates the use of a composition comprising : in the manufacture of a medicament for treatment and / or prophylaxis of muscle cramp and / or muscle stiffness in a mammalian subject . the present invention is now further described with reference to the following non - limiting examples . [ 0085 ] fig1 shows the motor nerve supply to most non - cranial nerve muscles . the central signal comes from the brain via the α - motor neurone with secondary signals to the muscle spindle from the β nerve route . the α - motor neurone initiates the contraction of the muscle whilst the muscle spindle and the golgi tendon organ provide negative or inhibitory feedback to the α - motor neurone to inhibit the neurone . the neurotransmitter that controls the inhibitory response is the amino acid glycine . glycine acts on the α - motor neurone by regulating the resting membrane potential . the glycine signal causes a change in chloride ion pumping which results in this change in resting potential . falls in the availability of glycine in the central nervous system will therefore resulting a reduction of the ability to inhibit the α - motor neurone . there are several methods by which changes in this system can effect the development of cramps : 1 ) the reduction in glycine availability . a low level of threonine and or high level of serine will be able to reduce glycine availability in the central nervous system , the neurones and their synapses . increased glycine conjugation in the liver through the glycine conjugation mechanisms will also reduce the available glycine and threonine ( kasuya et al ., 1996 ). 2 ) threonine transport disorders . a low level of threonine and or high level of serine will be able to reduce glycine uptake into the central nervous system or into the neurones and their synapses . threonine availability is important as it is transported across the blood brain barrier where as glycine is not . once threonine is transported it may then be converted to glycine for use in the cns . 3 ) electrolyte problems . sodium and chloride availability are significantly influenced by the amount of fluid and electrolyte replacement associated with exercise — particularly in competitive sport . these alterations may also be seen in various disease conditions where electrolyte availability is influenced by the disease process . 4 ) fall in high energy phosphate levels . this is usually associated with high exercise periods in sports people but may also occur in certain disease states . compound mg per gram l - glycine 350 mg l - threonine 150 mg sodium chloride 250 mg sodium phosphate 125 mg sodium bicarbonate 125 mg a 37 year old male had nocturnal muscle cramps for over 15 years and had tried all available drugs and remedies to correct the problem . one single 300 mg dose of the composition exemplified in example 2 prevented the development of cramps during the night for the first time in all those years . the patient was monitored on a regular basis over 2 years . the subject takes a small amount of the composition exemplified in example 2 every 1 - 2 weeks and has not developed nocturnal muscle cramps since the time of the first dose . a 27 year old sporting person who developed cramps regularly during sports events ( cricket ) took a 300 mg dose the supplement of example 2 before every cricket game and has not developed cramps since that time whilst playing cricket over a summer of sport . those skilled in the art will appreciate that the invention described herein is susceptible to variations and modifications other than those specifically described . it is to be understood that the invention includes all such variations and modifications . the invention also includes all of the steps , features , compositions and compounds referred to or indicated in this specification , individually or collectively , and any and all combinations of any two or more of said steps or features . kasuya f , igarashi k , fukui m . participation of a medium chain acyl - coa synthetase in glycine conjugation of the benzoic acid derivatives with the electron - donating groups . biochem pharmacol ; 51 : 805 - 809 , 1996 .
the present invention relates generally to muscle cramp and / or muscle stiffness and to a method for treating same . more particularly , the present invention provides a method for treating and / or reducing the likelihood of developing cram and / or muscle stiffness in a subject and to compositions effective in the treatment and / or prophylaxis of muscle cramp and / or muscle stiffness .