Bioequivalence of a Test Troche Formulation of Fentanyl Citrate (400 mcg) Compared to Actiq® 400 mcg, Cephalon, Inc.

Inclusion Criteria: * Males or non-pregnant, non-lactating females, 18 years of age or older with a minimum body weight of 120 pounds and a body mass index (BMI) between 19 and 29 inclusive. * Female subjects must be postmenopausal for at least one year, surgically sterile, or using a reliable method of contraception (oral, transdermal, or injectable hormonal contraceptive; condom with spermicide; IUD; abstinence, etc.) for at least 30 days prior to and for the duration of study participation. * Normal, healthy status confirmed by required screening assessments. * Subjects must be able to provide written consent and agree to abide by the study requirements. * Subjects must be able to demonstrate they understand and can perform the dosing procedure correctly using a placebo troche at check-in to Period 1. Exclusion Criteria: * If female, a positive pregnancy test at any time during the study, pregnant, lactating, or likely to become pregnant during the study. * Female subjects of childbearing potential who have not used adequate forms of birth control within 30 days of dosing. * History of conditions that might contraindicate or require caution be used in the administration of fentanyl or naltrexone, including: renal impairment, hepatobiliary or pancreatic disease, gastrointestinal obstruction, cardiac disease, obstructive pulmonary disease, acute or severe bronchial asthma, hypercarbia, elevated intracranial pressure, depleted blood volume, paralytic ileus, or hypersensitivity or idiosyncratic reaction to fentanyl, naltrexone, or any opioids. * History of any drug allergy, hypersensitivity, or intolerance which would compromise the safety of the subject or the study. * History of chronic alcohol, drug, or narcotic abuse, chronic use of tranquilizers, sedatives, aspirin, antibiotics, or other medications. * History of malignancy, stroke, or diabetes; cardiac, renal, liver, and pulmonary disease. * History of anxiety, tension, severe agitation, psychiatric disorders, psychosis, or mental depression requiring hospitalization, psychotherapy, and/or medication. * History or diagnosis of epilepsy or other seizure disorder. * History of abdominal and/or pelvic surgery within the last 5 years, except elective surgical sterilization. * History of acute abdominal conditions or gastrointestinal disease including, but not limited to, peptic ulcer, diverticulitis, bowel obstructions, adhesions, ileus, gastritis, and chronic diarrhea. * Subjects presenting with acute illness. * Administration of any other investigational drug during the 30 days prior to study entry. * Subjects who have smoked or used nicotine-containing products within 6 months prior to study entry. * Donation or significant loss of whole blood (480 mL or more) within 30 days or plasma within 14 days prior to study entry, including that withdrawn during the conduct of any other clinical study. * Positive test results for HIV, hepatitis B, or hepatitis C. * Positive test results for drugs of abuse or alcohol. * Subjects who have taken prescription drugs, except hormonal contraception, within 14 days or over-the-counter medications (including herbal preparations) within 7 days prior to study drug administration except for standard daily dose multivitamins, which are excluded after check-in to Period 2. * Any subject experiencing adverse events to the -13 and/or -1 hour doses of naltrexone, that in the investigator's opinion, are indicative of possible previous opioid use/abuse, or that would prevent tolerance of additional doses of naltrexone, will be withdrawn from the study prior to dosing with fentanyl. * Subjects with dental braces or partial dentures. * Subjects presenting with a history of gum disease.