Breakthrough PainAdministration, BuccalFentanylPainLabor PainAnalgesics, OpioidPain MeasurementAnalgesia, EpiduralChronic PainPain ManagementDouble-Blind MethodPain ThresholdChronic DiseaseNeoplasmsPain, PostoperativeBack PainLow Back PainPain, IntractableAbdominal PainNeck PainPelvic PainPain PerceptionFacial PainAcute PainPain, ReferredRadionuclide GeneratorsShoulder PainMusculoskeletal PainTreatment OutcomeLamivudineAnalgesics