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.
