Open Label, Safety Study of EN3270 in Patients With Moderate to Severe Non-malignant, Chronic Pain

Inclusion Criteria: * Opioid experienced * Hx (min 3 months) of moderate to severe pain of non-malignant that is well controlled with current pain therapy * On a stable dose of opioid medication for greater than or equal to 14 days * Have an adequate personal support system including a co-habitant * Are able and willing to follow verbal and written instructions and provide written informed consent Exclusion Criteria: * Are pregnant or lactating * Have pain secondary to a confirmed or suspected neoplasm * Have a history or physical examination finding incompatible with safe participation in the study * Have a history of alcohol or drug abuse * Have a history or physical examination finding of clinically significant skin abnormalities that would preclude use of a transdermal patch (e.g., psoriasis) * Have a history of or currently manifesting a clinically significant psychiatric disorder * Have a known history of allergy that negatively impacts respiratory function to a clinically significant level * Plan to have an MRI while on the study * Have any clinically significant condition that would, in the opinion of the investigator, preclude safe study participation * Are scheduled for surgery requiring general anesthesia within the study period