Bumetanide in Hypokalaemic Periodic Paralysis

Interested patients who provisionally meet inclusion/exclusion criteria will attend NHNN for a screening visit to check study eligibility and to have any questions relating to study participation answered. Each patient will undertake two assessment visits at approximately four weeks apart. Study participants will withhold carbonic anhydrase inhibitor medications for 72 hours prior to assessment visits as is standard for McManis testing and restart their routine treatment immediately after each visit. Participants will be admitted as an NHNN day case. Following baseline assessments a localised attack of weakness will be induced by isometric exercise of the abductor digit minimi (ADM) in the hand as per McManis protocol below. Participants will be randomly assigned to either bumetanide or placebo for the first visit. Identical appearing capsules will be prepared to blind both researcher and participant to treatment allocation. The assigned treatment will be taken by mouth at the onset of a focal attack defined as 40% decrement in ADM CMAP amplitude compared to the maximum CMAP amplitude recorded during or after the exercise. During the admission each patient will be monitored according to the research protocol. At the end of the assessment protocol the participant will be discharged home. The duration of each admission will be approximately 6 hours The second assessment will follow an identical protocol to the first, but with the other treatment administered.