the invention may be practiced on any substance capable upon injection of interrupting nerve impulse transmission across the neuromuscular junction . while many such neurotoxins are known , the currently most promising reagents of this type are the family of toxins derived from clostridium botulinum , and the most preferred is pharmaceutical grade botulinum toxin type a available commercially from allergan pharmaceuticals , inc . under the tradename oculinum . however , it should be stressed at the outset that it is a fundamental advantage and feature of the invention that it can be applied to any injectable substance which interrupts neuromuscular transmission at the synapse , and that other materials of this type when and if developed to pharmaceutical grade could be used in the novel therapies . thus , it is contemplated that other materials , protein subunits , recombinantly produced materials , and other various novel types of pharmaceutical preparations can be used in the practice of the invention to advantage . however the work forming the basis of the invention was conducted using the commercially available botulinum toxin - based material identified above , and the remainder of the discussion will be limited to this material , hereinafter referred to simply as &# 34 ; toxin &# 34 ;. injection of a sublethal dose of a toxin into muscle deposits a bolus of the material intramuscularly which diffuses outwardly to a distance that is a complex and currently unknown function of , inter alia , the identity and amount of diluent if any injected with the toxin , the mass of the toxin , the population of presynaptic receptors about the site of injection , and the then current physiological condition of the patient . diffusion , driven presumably by the concentration gradient , slows as active toxin binds to receptors on the . presynaptic membrane . some portion of the toxin is swept away by the vascular system and distributed systemically . some other portion may be proteolytically degraded before binding . doses far smaller than the ld 50 for man ( believed to be on the order of 2 μg ) can paralyze completely , or partially or lightly denervate a muscle volume , depending on dose . the therapetic effects are achieved at dosage levels in the range between a few i . u . to 500 to 1000 i . u ., preferably no more than 500 i . u ., and most preferably no more than 300 i . u ., administered as a plurality of injections about a muscle or muscle group . injection of a therapeutic dose results in destruction of a subset of the neuromuscular junctions innervating the muscle but leaves others in a functional state . it has been hypothesized that a threshold quantity of the toxin must bind to a particular axon before that axon becomes irreversibly poisoned and the denervation - renervation cycle is initiated . motor end plates which receive a dose below the threshold presumably recover and participate together with unaffected axons in continued innervation of the muscle . support for this model of drug action comes from the observations that : transient low level retardation of muscle stimulation can be detected in some cases in muscles remote from the site of injection ; an animal poisoned intraperitoneally with the toxin upon autopsy shows no histological signs of denervation , and ; there is a gradient of denervation about the site of injection . another factor affecting dose response is the existence of innervation zones within muscles , i . e ., there are differences in the microanatomical distribution of neuromuscular junctions within muscles . a literature search suggests that little is known about muscle innervation patterns . however , it is clear that some muscles are denervated more or less uniformly throughout their mass whereas others have a zone of innervation in one region . thus , particularly in large muscles , the locus of injection within the muscle can influence the physiological response . the extent of denervation of a muscle can be determined postmortem by sectioning the muscle and staining for acetylcholinesterase activity using the method of karnovsky ( see woolf and coers , the innervation of muscle . charles thomas pub , springfield , ill ., 1959 ). as disclosed below , excision of human muscle previously treated with the toxin , and postmortem sectioning of rabbit muscle about a site of toxin injection , exhibit a gradient of denervation akin to that disclosed by duchen in mice ( see j . neurol . neurosurg . 1970 : 33 : 40 - 54 ; j . physiol . ( lond ) 1969 ; 204 : 17 - 18 ). in accordance with the invention , the extent of spread of a given dose of a chemodenervating agent is used as a measure of the activity of the preparation , and is used to quantify an appropriate dose for injection into a muscle or muscle group . this permits the physician to confine the action of the toxin to a predetermined volume of muscle and to prevent or minimize the spread of the toxin into adjacent muscle tissue . for example , a given dose of a given preparation is injected into the muscle of an experimental animal . after three to five weeks , the animal is sacrificed , and in order to assess toxin spread of the injected dose , sections are taken about the site of injection , for example , 3 , 10 , 15 , 30 , 45 , and 60 mm from the site . each of the sections is stained to determine , for example , acetylcholinesterase activity . this permits visualization of the zone of effective denervation which can be determined rather precisely . alternatively , the muscle may be sectioned through the point of injection across the denervated field and stained so that the gradient can be observed readily . correlation of these data between , for example , small rodents and simians by direct observation , or between the experimental animals and surgically excised human muscle , backed by clinical experience , provide precise information on the zone and extent of denervation a given dose of toxin will induce when injected at a given site in a human . determination of the extent and zone of inhibition of acetylcholine release can be measured by various techniques known to those skilled in the art in addition to acetylcholinesterase staining , including single fiber electromyography ( see , for example , sanders et al , botulinum toxin for blephorospasm . single fiber emg studies . neurology , 85 ; 35 : 271 - 272 ) and by using labeled binding proteins such as polyclonal or monoclonal antibodies labeled with , for example , fluorescein of other fluorescent moiety , colloidal metallic particles , or other remotely detectable substance . antibodies can be produced , using known techniques , to acetylcholine receptors or to acetylcholinesterase , both of which can serve as a marker for effective denervation , or to epitopes which are newly exposed , or which remain after binding of the toxin to the receptor on the presynaptic motor end plate . other stains may be used such as hematoxylin , eosin , and masson trichrome . any of these techniques and others that can be devised may be used to determine the extent of diffusion and effective denervation of a given dose of a chemodenervating agent within the muscle of an experimental animal . use of the technique enables chemodenervating agents to be prepared in various dosage forms and provides nomograms which enable the physician to inject the agents for therapeutic purposes in humans responsibly while eliminating or minimizing side effects caused by unwanted toxin spread beyond the intended denervation zone . some degree of paresis and muscle weakening beyond the intended locus of denervating action may nevertheless occur . however , the physician may use the techniques and chemodenervating pharmaceuticals standardized as herein disclosed to tailor dose to the selected point or points of injection based on his diagnosis determining the affected muscles . the denervating effect therefore can be confined essentially to a given muscle or muscle groups despite the observation that botulinum toxin can spread beyond intervening facial planes and bony structures . data obtained using the process of the invention to date indicate clearly that the size of the field of action of therapeutic injections of chemodenervating agents is dose dependent . furthermore , several of the observed complications in established clinical protocols have been correlated to spread of the toxin beyond the intended field of action by retrospective and prospective study of the anatomic injection sites and doses . the sole figure of the drawing is a graph disclosing data representative of the type that can be generating using the process of the invention . longissimus dorsi muscle of groups of six new zealand white rabbits were studied to assess differences in acetylcholinesterase staining activity at varying distances from the site of injection of two separate doses of botulinum toxin . the first dose contained four to six i . u . as determined by dilution from a 100 i . u . vial of the commercial preparation ; the second contained 0 . 2 to 0 . 4 i . u . the toxin was reconstituted at 1 . 25 i . u . per 0 . 1 ml physiological saline . the point of injection was marked with a tattoo . the injections were made 5 to 8 mm deep directly into the muscle . a control animal was injected with the saline diluent . after five weeks , the animals were sacrificed , and sections of the muscle were taken 15 , 30 , and 45 mm caudel from the sites of injections transverse to the spine and in a direction parallel to the spine on the contralateral side . acetylcholinesterase slide staining was conducted by placing muscle specimens in baker &# 39 ; s solution ( 10 % formal - calcium ), which the were refrigerated , and after 24 hours , placed in 0 . 88 gum sucrose for 2 to 3 hours . the muscle then was sectioned into 10 micrometer sections in a cryostat at a - 20 ° c . and placed on gelatin - coated slides . acetylcholinesterase activity was demonstrated by karnovsky &# 39 ; s method , and the slides were incubated for 90 minutes at 37 ° c ., washed in distilled water , counterstained with fast green , dehydrated rapidly , and mounted . at the site of injection , diffuse acetylcholinesterase staining was seen over essentially all muscle fibers . for the larger dose , ( 2 to 3 i . u ./ kg ) the muscle histology was essentially identical at 15 mm . at 30 mms , a decrease in acetylcholinesterase enzymatic activity was indicated by a reduction in color intensity , but very significant muscle denervation was still apparent . at 45 mm , a very significant reduction in enzyme activity was noted . for the smaller dose ( 0 . 1 to 0 . 2 i . u ./ kg ) immediately about the site of injection enzyme activity was similar to the larger dose . however , at 15 mm from the site of injection , denervation was markedly diminished , and at 30 mm and 45 mm , enzyme activity was barely above levels observed in control specimens . contralateral longissimus dorsi biopsy specimens revealed staining intensities similar to those observed in the specimens discussed above , illustrating that toxin diffuses unhindered through facial planes and about bone . these results demonstrate the feasibility of the standardization process of the invention . that such results can be used to improve the clinical efficacy of botulinum preparations was demonstrated in the clinic as follows . retrospective reviews were conducted from the records of patients with adult onset idiopathic spasmotic torticollis who had been given botulinum a toxin for a period of two to thirty - eight months ( average 1 . 1 years ) and who had experienced the complications of dysphagia ( difficulty in swallowing caused by paresis ). in these patients , the toxin had been reconstituted in normal saline (≃ 100 i . u ./ ml ) without preservative and injected with a 25 or 27 gauge needle . patients had been evaluated bi - weekly or immediately for evidence of dysphagia . a single treatment consisted of one or more injections to the sternomastoid muscle or to the posterior cervical muscles , or both . the muscles injected had been determined to be dystonic based on palpation , hypertrophy , involuntary spasms , and posture deformity . each of the 49 injections to the cervical musculature of 26 patients was characterized with respect to dose and injection site . the injections that did not result in dysphagia were then compared with those that did . the data from this retrospective analysis indicated a potential cause - effect relationship between the dysphagia and sternomastoid dosage . analysis of the data indicated that each patient who experienced dysphagia noted the onset of symptoms within 20 days of the injection and reported a duration of from six days to four weeks . there was no significant difference between total dosage given patients who experienced dysphagia and those who did not . however , if the dose given to individual muscles was evaluated , a significant difference in the dose administered to the sternomastoid muscle was apparent . more specificially , every patient who had experienced dysphagia had had 150 i . u . to 175 i . u . injected into the sternomastoid muscle . in addition to numeric analysis of dose , every patient who experienced dysphagia had been injected in their sternomastoid muscle , and the complication did not occur if the posterior cervical muscle group was alone injected . thereafter , 24 patients were enrolled for a prospective study and were asked to report to the investigator promptly should dysphagia occur . each patient was contacted within four weeks of injection and specifically questioned to assess whether post - injection dysphagia had occurred . each of these patients were given a dose not greater than 100 i . u . in the sternomastoid muscle at three , four , or five injection points , typically five , of 20 to 35 i . u . per injection site . in addition , eight additional injections were given to six patients who initially experienced dysphagia yet benefited substantially from the previous treatment . patients from this group were injected after a period of at least five months from the previous injection with a sternomastoid dose of 100 i . u ., again in 3 to 5 points along the length of the muscle . none of the next 31 injections in the 24 patients were followed by dysphagia . furthermore , the six patients previously experiencing dysphagia who received eight injections under the new treatment protocol showed no reoccurrence of dysphagia after 20 weeks follow - up . these data indicate that injection of 100 to 175 i . u . ( 2 - 3 i . u ./ kg ) into the sternomastoid can result in diffusion of the botulinum preparation into deeper muscles of the throat resulting in dysphagia manifest by difficulties in speaking , swallowing , or breathing . in contrast , smaller doses of 20 to 30 i . u . spaced 5 - 15 mms apart , limiting the total does to less than about 100 i . u . (& lt ; 2 i . u ./ kg ) in the sternomastoid resulted in no deep muscle involvement causing dysphagia . in these patients the sternomastoid is about 30 mm from the pharanx . these data are supported further by the histological observation of strips of obicularis oculi muscle ( normally discarded ) excised from patients undergoing ptosis surgery who had been treated previously with botulinum a for involuntary blepherospasm , and control specimens of obicularis oculi excised from patients with involutional ptosis who had never been injected with botulinum toxin . the test specimens were obtained four weeks to four months after the last botulinum toxin injection and each was treated to assess denervation as disclosed above . each toxin treated muscle specimen exhibited extensive spread of acetylcholinesterase activity over the individual muscle fibers . the diffuse pattern of staining , which was associated with muscle fiber atrophy , made identification of discrete neuromuscular junctions difficult . in contrast , each of the four control specimens showed discrete areas of staining on the muscle fiber surface corresponding to acetylcholinesterase activity and position of neuromuscular junctions of the muscle fiber . these and other observations from the clinical treatment of blepharospasm indicate that 20 i . u . botulinum toxin ( 0 . 2 - 0 . 4 i . u ./ kg ) will spread less than about 30 cm in human obicularis oculi . in accordance with the invention the toxin may be prepared in dosage form in conventional biologic standardizations such as ld 50 but most importantly in terms of a unit dose of the toxin &# 39 ; s spread capability . this involves nomagram preparation as outlined above and labeling the pharmaceutical agent with the information to provide the physician with the capability of placing injection sites at preselected intervals on the muscle selectively to denervate the muscle and to limit toxin spread in contiguous muscles . this permits expansion of use of the preparations into procedures such as those described below . the involuntary grinding of teetch characteristic of true bruxism is caused by involuntary contractions of the masseter , temporalis and pterygoid muscles . the masseter and temporalis usually are targeted as the muscles which will undergo chemodenervation . they are injected so as to limit the penetration of the toxin to the volume and body of the muscles . diffusion should be limited to a distance of no more than 25 to 35 mms . a unit dose injection is given at the surface of each of these muscles at multiple points percutaneously or permucosally . of course , appropriate dental evaluation to assess the degree of damage or potential damage to the teeth should be conducted prior to application of the toxin . the treatment is repeated periodically , e . g ., at three to five month intervals as needed to inhibit jaw clenching to protect the teeth , and to relieve the pain syndrome , if any . facial expression lines such as the transverse forehead lines or the nasolabial fold are created by attachments of projections of facial muscles into the dermis . contraction of facial muscles generally is well known to produce the various characteristic forms of facial expressions such as smiling , grimacing , etc . in addition , exaggeration of facial lines also is associated with the aging process . the general principle of the application of the toxin is to limit the tonic contractile state of facial muscles so as to reduce muscle tone and to improve or change the quality and characteristics of facial expression . the transverse forehead lines may be reduced in intensity by injecting a quantity of toxin with a diffusion field of approximately 5 to 10 mms in four injection sites at the superior border of the forehead and at a point approximately 15 mms superior to the brow . this is done symmetrically on both sides of the forehead . the glabellar lines ( the frowning lines in the mid position of the forehead ) may be targeted by treated the glabellar muscles with a toxin quantity producing a field of denervation of 5 to 10 mms the toxin is injected 15 mms . above the brow line in the mid position of the forehead . the nasal labial fold lines can be diminished in their intensity by treating the zygomatic major and minor muscles which emanate from the zygomatic arch and extend diagonally to the position of the nasal labial fold . an injection of toxin diffusing a distance of 5 to 10 mms over the superior border of these muscles will diminish this line effectively . furthermore , the position of the lips can be controlled by injecting the zygomatic major and minor muscles . the protrusion of the upper lip can be reduced and even inverted by injection of these muscles . in addition , the protrusion of the lower lip can be reduced by injecting the mentalis muscle at doses producing a denervating field of 5 to 10 mms at the level of the chin approximately 15 mms inferior to the lower lips at a point of approximately 5 mms from the midline . cerebrovascular injuries ( stroke and cerebro - spinal injury ) can cause spasticity and contractions as a result of paralysis and spasticity . although the toxin produces a paralysis , it can be useful in reducing muscle mass and in helping spasticity . symptomatic spasticity can result in chronic involuntary movements as well as difficulties with contracted postures or contractions of the limbs . the application of the drug to these spastic states involves knowledge of innervation zones of limb muscles , ( see , e . g ., woolf et al , supra ). the muscle which is involved in the abnormal posture or abnormal movement can be identified with an electromyographic needle . such muscles can also be identified as causing the posture deformities based on experience and an understanding of the muscle &# 39 ; s contractile states on the limb position and movement capabilities . these muscles are impaled with a needle at a site close to the innervation zone . in certain situations , it may be necessary to stimulate the muscle with a stimulating current through a teflon coated electromyographic needle to insure the correct placement of the injections . the toxin is injected at a dose level appropriate to create a field of denervation encompassing the innervation zone of the muscle or the entire muscle . multiple injections over long muscles may be necessary to isolate the effect over that muscle . cerebral palsy results from various forms of brain damage related to anoxia or vascular insufficiency , usually at the time of birth . the destruction of the central cortex of the central motor system results in involuntary movement spasticity , abnormal posturing , and unwanted contractures of muscles . physical therapy and occassionally antispasmodic drugs are used to treat cerebral palsy . in situations where spasticity is involved with pain , deformity , involuntary movements , or limitations in functional capabilities of a patient , use of the toxin may be indicated . application involves targeting muscle groups vital to the patient &# 39 ; s disability such as muscles which produce limb deformities or impairments in the volitional movements , or in situations where contractures seem to be developing into abnormal postures . the dosage for treatment of this disease will involve targeting these muscles and using a formulation similar to that used to treat cerebrovascular disease . the prototype for large muscle applications is spasmotic torticollis . the targeted muscles is injected with a dose sufficient to encompass the innervation zone of the muscle . multiple sclerosis is a disease of white matter of the central nervous system . it involves a demyelination process which leads to impairment of the cortical spinal track and associative tracks in the brain stem . this leads to spinal damage and resultant spasticity . spasticity in multiple sclerosis can be debilitating because of involuntary movement , contracture , posture deformities , and in certain situations , pain . use of the toxin is directed and targeted at indications which relieve these particular afflictions relative to the management of the disease . again , the toxin is targeted at muscles determined by the physician , neurologist , podiatrist or orthopedic surgeon that appear to be hyperactive . the muscles are injected with a quantity sufficient to encompass volumetrically the muscle or its innervation zone , or both . a working knowledge of muscle anatomy , innervation , and functional anatomy will be needed by the practitioner to achieve optimum results . parkinson &# 39 ; s disease is characterized by three basic defects : akinesia ( lack of movement ); tremor ( involuntary movement ); and rigidity ( increase muscle tone in muscle groups ). the toxin can be used to improve the degree of tremor and rigidity present in parkinson &# 39 ; s disease although it probably will be contraindicated in akinesia . in certain situations in parkinson &# 39 ; s disease severe dystonias develop in the patient &# 39 ; s limbs . in these situations , the involuntary movements are exaggerated , spastic , and often painful . toxin is injected into the muscle in a dose sufficient to encompass the volume of the muscle or its innervation zone or both . it is done with a stimulating electrode needle to an emg machine or in conjunction with emg machine to insure the correct placement of the needle in the muscle . the toxin is given in multiple injection points for large muscles in order to insure an adequate percentage of the innervation zone is encompassed in the injection formulation . the toxin injections must be repeated every three to six months to sustain the desired clinical effect . total dose administered to initiate a given cycle of denervation -- reinnervation should in all cases be far below the ld 50 for the patient . the invention may be embodied in other specific forms without departing from the spirit and essential characteristics thereof .
this invention relates to a method for controlled administration of chemodernervating agents such as botulinum toxin - derived pharmaceutical , useful in attenuating neural stimulation and spasmotic activity of muscle . the method involves administration of novel dosage forms based upon the standardization of denervating pharmaceuticals . the invention also relates to novel methods of administering chemodernervating agents in a controlled and reproducible manner so as to confine their effects to a given region of muscle mass while minimizing paresis in adjacent muscle tissue .