A Study Comparing the Effectiveness and Safety of Tramadol HCl/Acetaminophen Versus Placebo for the Treatment of Painful Neuropathy in Diabetic Patients

• Change in the average of daily pain score recorded in the IVR system from baseline to the patient's final week of treatment with study medication.
  

• Efficacy measured by Brief Pain Inventory, Visual Analogue Scale, Short-Form McGill Pain Questionnaire, Profile of Mood States, SF-36 Health Survey, Physician and Subject Global Impression of Change, average daily sleep interference
  

Previous studies have shown that tramadol HCl is effective in painful diabetic neuropathy. The treatment of neuropathic pain often requires the use of more than one medication, working through different mechanisms of action, to provide the best pain relief. The pain-relieving potential of tramadol HCl /acetaminophen for the treatment of painful diabetic neuropathy comes from the multiple mechanisms of action in this combination pain medication. This is a multicenter, randomized, double-blind, placebo-controlled, parallel group study. Patients who experience painful diabetic neuropathy will be enrolled. There will be a period of up to 3 weeks during which patients will stop taking medications not allowed by the study. A 7-day baseline period will follow, during which time patients will call into an Interactive Voice Response (IVR) system every night at bedtime to record daily assessments including average daily pain and sleep interference. Patients who enter the double-blind portion of the study will be randomized (like with the toss of a coin) to receive either tramadol HCl/acetaminophen or placebo. The dose of tramadol HCl/acetaminophen or placebo will be gradually increased until the doctor determines the patient is taking an adequate dose; up to 1 or 2 tablets 4 times per day, but not more than 8 tablets per day. Every night at bedtime during the double-blind phase, patients will call the IVR system to report assessments of average daily pain, sleep interference and the number of tablets of study medication taken that day. At the end of the study, patients will be tapered off their study medication. The objective of this study is to compare the analgesic effectiveness and safety of tramadol HCl/acetaminophen versus placebo for the treatment of painful diabetic neuropathy.

1 or 2 tramadol HCl (37.5 milligrams)/acetaminophen (325 milligrams) combination tablets or matching placebo by mouth up to 4 times a day for 66 days