The present invention provides novel methods for classifying, diagnosing and/or treating a group of human and veterinary ailments involving endogenous opioid concentrations. Also provided is a novel use for an existing class of compounds, the opioids, to treat opiopathic ailments, particularly paresis/paralysis, pseudo-atrophy and/or opiopathic pain, and in the manufacture of pharmaceutical and veterinary formulations therefor. The invention also relates to neuropathic, polyneuropathic, neurologic and neurogenic ailments typically characterized by paresis/paralysis. These ailments can involve an abnormal concentration of one or more endogenous opioids, or the blockade, underexpression or overexpression of one or more opioid receptors. In that regard, the invention encompasses therapeutic uses, methods and compositions employing opiates and/or their receptors. In particular, the invention relates to certain laboratory testing methods, clinical testing methods, research and development methods, business methods, methods of treatment, novel therapeutic uses, and human and veterinary pharmaceutical dosage forms, dosing regimens and formulations, especially those pertaining to opiopathy (particularly hypo-opiopathy).