Clinical experience with eperisone in the treatment of acute low back pain.

Aim: A muscle contracture is the main responsible for low back pain and it consists of a persistent and involuntary muscle shortening, but it may be also the consequence of back pain thus fostering the painful condition. The goals of a pharmacological treatment for acute low back are, therefore, not only the relief of pain, but also the reduction of muscle spasm and inflammation, since nociception often results from local secondary inflammation and muscle spasm. Although systematic reviews have shown that muscle relaxants are effective in the management of non-specific low back pain, the use of these compounds is often limited by adverse effects on central nervous systems (CNS), such as drowsiness. Thus, the effects of eperisone, a new muscle relaxant agent with no CNS adverse effects, have been investigated.

Methods: A total of 100 patients (38 males and 62 females) with acute low back pain and moderate contracture of the spinal muscles arisen since less than 48 h were enrolled in the study. After physical examination, these patients were treated with eperisone 50 mg every 8 h for 10 consecutive days and were visited again after 3 days and at the end of treatment.

Results: Only 4 patients (4%) were obliged to stop treatment because of minor gastrointestinal adverse reactions. The administration of eperisone resulted in a prompt reduction of both spontaneous and provoked pain, as well as in a progressive decontracture of spinal muscles, as suggested by a reduction in resistance to passive movement, antalgic rigidity and ''hand-to-floor'' distance.

Conclusion: Eperisone is thus a muscle relaxant agent, with a mechanism of action slightly different from that of other muscle relaxants. In addition to an inhibition of mono- and multisynaptic reflexes in the spinal cord and supra-spinal structures, eperisone regulates the blood supply to skeletal muscles; this action is noteworthy since a muscle contracture may compress the small blood vessels and induce an ischemia leading to release of nociceptive compounds. Most importantly, eperisone is devoid of detrimental effects on CNS.