the composition of the present invention is a non - racemic mixture of d - methadone and l - methadone , with the proportions being tailored to the needs of a particular patient . in one aspect , the inventive method comprises the administration of a non - racemic mixture of d - and l - methadone with each of the two methadone isomers being present in an effective amount to relieve a particular type of pain . in another preferred aspect , the inventive method comprises the administration of a non - racemic mixture of d - and l - methadone with the proportions of the two methadone isomers being adjusted to meet the needs of a particular patient . in yet another aspect of the present invention , naloxone naltrexone , or the like , is administered in an effective amount to eliminate mu - receptor activity with the non - racemic methadone mixture of the present invention or with racemic dl - methadone or l - methadone . the optical resolution of methadone may be accomplished by any of several methods well - known in the art . for example , through the use of d - tartaric acid . dl - methadone , or its hydrochloride , may be resolved by forming the easily purified , water - insoluble d - α - bromocamphor - n - sulfonate of the d - isomer . pure d - methadone is precipitated by slow addition of water . the l - form is obtained , from the mother liquor , by forming the d - tartrate salt . a method for simultaneous resolution of both optical isomers of dl - methadone is taught in u . s . pat . no . 2 , 983 , 757 , which is incorporated herein by reference . the method is based on the knowledge that a seed crystal of the dextro - rotatory isomer will attract the d - isomer in saturated solution , and when the degree of saturation of the solute in the solution is increased , the d - isomer will tend to crystallize out on the d - isomer seed crystal . at the same time , a portion of the l - isomer will tend to crystallize out on the l - isomer seed crystal . this process will continue so long as the solution is supersaturated with the composition or solute and seeded crystals will grow to substantial size . at the conclusion of the operation , it will be found that relatively pure crystals of the d - isomer and l - isomer will have been grown on the seed crystals . the methadone mixture of the present invention may be administered in any form well - known in the art . administration may be oral ( including immediate release and continuous release forms ); rectal ; parenteral ( for example , intravenous , intramuscular , subcutaneous , intraventricular , intrathecal , epidural , intracerebroventricular ); transcutaneous , intranasal , sublingual , transbuccal , transsclerol , or intraosseous injection . the composition may be administered by means of a transdermal device such as a patch . any other well - known means of delivery may be used , it being distinctly understood that the foregoing list is not all inclusive . the composition will ordinarily be formulated with one or more pharmaceutically acceptable ingredients in accordance with known and established practice . thus , the composition can be formulated as a liquid , powder , elixir , injectable solution or suspension , etc . formulations for oral use can be provided as tablets , caplets or hard capsules wherein the pharmacologically active ingredients are mixed with an inert solid diluent such as calcium carbonate , sodium carbonate , calcium phosphate , lactose , talc , or kaolin , or as soft gelatin capsules wherein the active ingredients are mixed with an oleaginous medium , e . g ., liquid paraffin or olive oil . tablets may also include granulating and disintegrating agents such as starch , gelatin , and acacia , and lubricating agents such as magnesium stearate , stearic acid , and talc . tablets may be coated or uncoated . inert diluents and carriers which may be used in capsules include , for example , calcium carbonate , calcium phosphate , and kaolin . aqueous suspensions can include pharmaceutically acceptable excipients such as suspending agents , e . g ., sodium carboxymethyl cellulose , methylcellulose , hydroxypropylmethyl - cellulose , sodium alginate , polyvinylpyrrolidone , gum tragacanth and gum acacia ; dispersing or wetting agents such as naturally occurring phosphatide , e . g ., lecithin , or condensation products of an alkylene oxide with fatty acids , e . g ., polyoxyethylene stearate , or condensation products of ethylene oxide with long chain aliphatic alcohols , e . g . heptadecaethylene - oxycetanol or condensation products of ethylene oxide with partial esters derived from fatty acids and a hexitol , e . g ., polyoxyethylene sorbitol monoleate or condensation products of ethylene oxide with partial esters derived from fatty acids and hexitol anhydrides , e . g ., polyoxyethylene sorbitan monooleate . the aqueous suspensions can also contain one or more preservatives , e . g ., ethyl - or - n - propyl - p - hydroxy benzoate , one or more coloring agents , one or more flavoring agents and one or more sweetening agents , such as sucrose , saccharin or sodium or calcium cyclamate . the dosage of the composition will vary widely according to a number of factors . the treatment of pain is an art which relies on empirical factors more than the treatment of other types of ailments . thus , the makeup of the composition will vary as will the dosage . in one preferred embodiment , the composition will contain an effective amount of d - methadone for relieving neuropathic pain and an effective amount of l - methadone for relieving somatic pain . in another embodiment , the non - racemic proportions of the d - and l - isomers of methadone can be predetermined and the composition administered in an amount effective to relieve the patient &# 39 ; s pain regardless of the source of the pain . the actual dosages can very widely from about 5 to about 300 mg / day . depending on the frequency of administration , the amount of each could be from about 1 to about 100 mg per unit dose . the composition of this invention may optionally include an analgesic of the nonopioid type . useful nonopioid analgesics include the coal - tar analgesics , in particular , acetaminophen , and nonsteroidal anti - inflammatory drugs ( nsaids ) such as aspirin , diclofenac , diflusinal , etodolac , fenbufen , fenoprofen , flufenisal , flurbiprofen , ibuprofen , indomethacin , ketoprofen , ketorolac , meclofenamic acid , mefanamic acid , naburnetone , naproxen , oxaprozin , phenylbutazone , piroxicam , sulindac , tolmetin , zomepirac , their mixtures and their pharmaceutically acceptable salts . the composition of this invention may also include a skeletal muscle relaxant or combinations of any of the foregoing . this component may be amobarbital , aprobarbital , butabarbital , mephobarbital , metharbital , methohexital , pentobarbital , phenobarbital , secobarbital , talbutal , theamylal , thiopental and their pharmaceutically acceptable salts and the norbarbiturate sedatives include benzodiazepines having a sedative action such as chlordiazepoxide , clorazepate , diazepam , flurazepam , lorazepam , oxazepam , temazepam , triazolam and their pharmaceutically acceptable salts , h 1 antagonists having a sedative action such as diphenhydramine , pyrilamine , promethazine , chlorpheniramine , chlorcyclizine and their pharmaceutically acceptable salts , neuroleptics such as droperidol and miscellaneous sedatives such as glutethimide , meprobamate , methaqualone , dichloralphenazone and their pharmaceutically acceptable salts . skeletal muscle relaxants may include baclofen , carisoprodol , chlorzoxazone , cyclobenzaprine , methocarbamol , orphrenadine and their pharmaceutically acceptable salts . in addition to the components already cited , the composition of the present invention can contain one or more other pharmacologically active components , e . g ., a stimulant such as caffeine ; an antihistamine such as chlorpheniramine maleate ; a decongestant such as phenylephrine hydrochloride or phenylpropanolamine hydrochloride ; a sympathomimetic such as isometheptene mucate ; and / or an anticonvulsant such as gabapentin , phenyloin , carbamazepine , valproate , or clonazepam . the composition of the present invention is designed to treat a variety of pain conditions , especially chronic pain . although the invention has been described with reference to a specific embodiment this description is not meant to be construed in a limiting sense . on the contrary , various modifications of the disclosed embodiments will become apparent to those skilled in the art upon reference to the description of the invention . it is therefore contemplated that the appended claims will cover such modifications , alternatives , and equivalents that fall within the true spirit and scope of the invention .
compositions of non - racemic mixtures of d - and l - methadone and a method of treating pain using the composition . the composition is especially useful for treating pain of mixed origin . for predominantly neuropathic pain , a mixture of predominantly d - methadone , up to about 90 %, is used . for predominantly somatic pain , a mixture of predominantly l - methadone , up to about 90 %, is used . the non - racemic mixture of d - and l - methadone may be further combined with a pharmacologically effective amount of a nonopioid component . in another aspect of the invention , the methadone can be combined with an opioid antagonist such as naloxone , naltrexone , or the like .