The primary objective of this study is to determine the time of onset of analgesic effect of Tramadol Contramid® Once-A-Day (OAD) in acute low back pain. Secondary objectives include determining the relationship between analgesic effect and plasma levels for Tramadol Contramid® OAD and to examine safety after single dose administration of 200 mg of Tramadol Contramid® OAD.

Inclusion Criteria:

• Males or females in generally good health aged 18-80 years with acute low back pain are eligible for this study.
• Patients must have pain of moderate to severe intensity on the patient rating of pain intensity scale without analgesia.
• Oral and written language comprehension at a level sufficient to comply with the protocol and complete study-related materials.
• Must have signed and dated an REB-approved written Informed Consent form which was also signed and dated by the Investigator prior to study participation.

Exclusion Criteria:

• Known history or symptoms suspicious of:

  • Spinal fracture
  • Cancer (i.e. constitutional symptoms such as recent unexplained chills or weight loss)
  • Spinal infection (e.g. IV drug abuse, immunosuppression)

• Cauda equina syndrome

• Spina bifida

• Foot drop

• Spinal surgery within 1 year of study entry

• Body Mass Index (BMI) > 37

• Continuous chronic back pain

• More severe pain in a region other than the lower back

• Treatment of the back pain with non-pharmacological therapy (e.g. acupuncture chiropractic adjustment, Transcutaneous Electrical Nerve Stimulation, physiotherapy etc.) in the 3 weeks prior to study entry

• Use of any sedative hypnotics, topical preparations/medications and anaesthetics or muscle relaxants within 5 half-lives of the dose of study medication

• Use of any analgesic within 6 hours of the dose of study medication. In rare cases, if a patient is in moderate to severe pain despite having taken a short-acting analgesic and if at least 2 hours have passed since the dose of short-acting analgesic, the patient may be entered.

• A major illness, requiring hospitalisation during the 3 months before commencement of the screening period

• Unwillingness to stop taking pain medication other than the study medication

• Previous failure of treatment with tramadol or discontinuation of treatment with tramadol due to adverse events

• Treatment within the last 3 weeks with any of the following medications: monoamine oxidase inhibitors; tricyclic antidepressants and other tricyclic compounds (e.g. cyclobenzaprine, promethazine); neuroleptics; selective serotonin reuptake inhibitors (SSRIs); serotonin-norepinephrine reuptake inhibitors (SNRIs) or any other drug that reduces seizure threshold

• Treatment with another investigational agent within the last 30 days

• History of seizure disorder other than Infantile Febrile Seizures

• Previous or current opioid dependency

• Bowel disease causing malabsorption

• Pregnant or lactating women

• Known significant liver disease or symptoms of significant liver disease

• Known significant renal disease or symptoms of significant renal disease

• Current or past substance abuse or dependence, other than nicotine

• Allergy to tramadol or any structurally similar drugs (e.g. opiates)

• Any other condition that, in the opinion of the Investigators, would adversely affect the patient's ability to complete the study or its measures