If taking a prescription medication (with the exception of prescription formulations of NSAIDs, acetaminophen, and aspirin) episodically for the management of pain, the subject must agree to discontinue its use prior to or at the baseline visit. If taking a prescription medication daily for the management of pain, must agree to continue the daily use of the medication throughout the 16-week observation period. If taking an over-the-counter pain medication daily, the subject must agree to continue the daily use throughout the study.