Commentary

RLS is currently diagnosed clinically, because no confirmatory laboratory test is available, and is treated with such drugs as levodopa, dopamine agonists, and opioids. Practice parameters of the American Academy of Sleep Medicine favour dopaminergic agents for the treatment of RLS.¹ The choice of outcome measures used in clinical trials in RLS is very important. Although validated rating scales have been used in some studies,² the study by Garcia et al applied a new rating scale that is subjective and not yet validated.

RLS is a lifelong condition, whose symptoms may gradually worsen with age. To assess clinically relevant outcomes of new drug treatments, their short term efficacy must be unequivocally affirmed before doing long term evaluations.

Although this study provides support for a possible new treatment, it does not provide sufficient evidence about the efficacy of gabapentin for RLS. A particular concern is the risk for a carryover effect, which was not considered in this study. The 1 week washout period between gabapentin and placebo was probably calibrated on the half life of gabapentin (5–7 h), although no evidence exists that its clinical action is short lasting. Blinding of the treating physician is another concern because gabapentin was increased during the study based on therapeutic efficacy. Inadequate blinding may have influenced the outcome by the use of subjective elements in the rating scales. Furthermore, the results for gabapentin and placebo were presented separately, whereas in a crossover design, it is better to report within individual comparison of treatments (paired analysis). The safety of gabapentin remains unclear, because the incidence of adverse events from gabapentin was relatively substantial (48%). Based on the available information, gabapentin should not be considered a first choice treatment for RLS.