A systematic review involving 50 randomized controlled trials (4,863 patients) published since 1980 was undertaken with the objective of assessing efficacy and safety of low back pain (LBP) medications. The methodological quality of each trial was evaluated based on a standardized system. Quality scores ranged from 26 to 82 points on a 100-point scale (from 0 to 100), indicating an overall moderate quality of the trials reviewed. Limited evidence was found regarding the effectiveness of drug treatments for LBP and current studies focused on short-term usage of the therapies. Available evidence supported the effectiveness of non-selective nonsteroidal anti-inflammatory drugs (NSAIDs) in acute and chronic LBP, of muscle relaxants in acute LBP, and of antidepressants in chronic LBP; safety results were heterogeneous. More rigorously designed trials should be implemented to establish comparative efficacy and safety of drugs used to treat chronic and acute LBP.