Inclusion Criteria:  Healthy male/female volunteers >18 years No allergy to naloxone or ingredients in its formulation Ability to read and understand English Written informed consent obtained from subject Ability to comply with study requirements  Exclusion Criteria:  History of alcohol or substance abuse History of unusual pain sensitivity, lack of sensitivity History of chronic myofascial, inflammatory, neuropathic pain Chronic use of medication known to interfere with naloxone Pregnant women and nursing mothers Presence of a condition or abnormality that in the opinion of the Principal Investigator would compromise subject safety or the quality of the data (e.g., persons with liver disease, renal insufficiency/failure) Alcohol on the breath