Tolerability, Safety and Activity of a Muscle Relaxant Molecule IDN5243 in Patients With Low Back Pain

Inclusion Criteria: * Male or female patients, * 18-70 years old inclusive, * Signed Informed consent obtained prior the inclusion in the trial, * A diagnosis of LBP equal to or greater than 50 mm on VAS with severe or moderate lumbar muscle spasm naïve or in relapsing condition, * Patients must have a medical history, physical and neurological examinations that support a clinical diagnosis of acute LBP that is felt down to the lower leg below the knee with the onset no longer than 30 days before Visit 1, * Patients must be appropriate candidates for treatment with study medication in the Investigator's clinical judgment, * Patients must be able to appropriately verbalize pain characteristics and to complete all protocol required measurements/assessments without assistance, * Patients must be medically stable on the basis of physical examination, medical history, vital signs, and clinical laboratory tests performed at screening. Exclusion Criteria: * LPB of non-mechanical origin such as neoplasm, infection or inflammatory chronic disorder, * Serum creatinine level \> 1.7 mg/dL or Urea \> 17 mmol/l, * Severe to mild hepatic dysfunction, * Abnormal blood count, * Ascertained or presumptive hypersensitivity to the active principle and/or formulations' ingredients, * History of anaphylaxis to drugs or allergic reactions in particular, history of hypersensitivity reactions (e.g. bronchospasm, rhinitis, urticaria) to drugs including to paracetamol, * Patients with diabetic neuro…