LAUSR

ABSTRACT Introduction: The periodic paralyses (PP) are rare genetic neuromuscular disorders that cause significant morbidity with episodic symptoms of muscle paralysis lasting from hours to weeks. There are no consensus treatment guidelines. Current treatment options include diuretics and the carbonic anhydrase (CA) inhibitor acetazolamide ACZ, but only anecdotal evidence and case reports support their use. Areas covered: We consider the evidence for the CA inhibitor dichlorphenamide. This is the only treatment for PP to have undergone randomised controlled trials. Although there has never been a comparative trial of dichlorphenamide and ACZ, many patients anecdotally report greater benefit from dichlorphenamide. However, it has been unavailable worldwide since 2011 until its recent re-introduction to the market in late 2015. Expert opinion: There is level I evidence for the efficacy of dichlorphenamide in PP. The ubiquitous nature of CA enzymes mean that systemic administration of a CA inhibitor leads to common dose-dependent side effects. In hypokalaemic periodic paralysis the benefits seem to outweigh these with acceptable tolerability. A successful consequence of recent randomised controlled trials was the re-introduction of dichlorphenamide to the commercial market following FDA approval in August 2015. Orphan status of dichlorphenamide for the treatment of PP is to be welcomed but the current pricing is potentially prohibitive.