The effective management of chronic pain conditions such as low back pain requires a comprehensive therapeutic approach; this usually includes physiotherapy, sometimes surgery and frequently pharmacotherapy. Treatment of low back pain is intended to reduce pain and to restore mobility and muscle strength. The drugs most commonly used are NSAIDs which may be beneficial in some cases as they possess both analgesic and anti-inflammatory properties. However, long-term use is often associated with a high risk of gastrointestinal complications such as ulcer and bleeding.

Thus, clinicians frequently are in search for an alternative medication. Tramadol is a therapeutic option for the long-term treatment of moderate to severe low back pain due to the absence of adverse drug reactions such as gastrointestinal irritation. The absence of severe adverse events on respiratory and cardiovascular function and the low incidence of constipation offer further advantages.

Tramadol hydrochloride is a synthetic centrally acting analgesic with a novel mechanism of action.[1,2] Tramadol has a weak affinity for opioid receptors binding preferentially to the m-receptors but also inhibits both norepinephrine (noradrenaline) and serotonin (5-hydroxytryptamine) neuronal reuptake and facilitates its release.[2,3] The dual mode of action has prompted the classification of tramadol as a non-narcotic centrally acting analgesic. In most animal models, the analgesic action of tramadol is attenuated, but not blocked, by naloxone.

Although the analgesic efficacy of tramadol has been demonstrated in numerous clinical trials for a variety of indications, there are only few published data on tramadol in a sustained-release form for use in low back pain. Therefore, the objective of this study was to investigate whether tramadol SR 100mg capsules twice daily are as efficacious as tramadol IR 50mg capsules four times daily in the treatment of moderate to severe chronic low back pain. The secondary objective was to compare the tolerability of the two formulations.