N-of-1 trial of salbutamol in hyperkalaemic periodic paralysis

Authors: Stunnenberg, Merkus, Raaphorst, Saris, Groenewoud, Statland, ... & van der Wilt (2021).

Hyperkalemic periodic paralysis (HyperPP) is a rare neurological channelopathy characterized by disrupted sarcolemmal membrane excitability. Clinical features include episodic muscle weakness attacks with associated rise in serum potassium and a degree of myotonia. Salbutamol, which is believed to increase the cellular uptake of potassium, has occasionally been used as an attack treatment. Stunnenberg et al. (2021) conducted a N-of-1 trial comparing salbutamol use versus placebo treatment to test whether salbutamol treatment reduce weakness attacks features to a clinically meaningful degree in a single patient with HyperPP. This N-of-1 trial consisted of a randomised, placebo-controlled, double-blind, single patient, multiple cross-over trial with two treatment sets (2-week treatment period and 2-week placebo period). In this case, the N-of-1 trial provided personalised, level-1 evidence that salbutamol treatment did not reduce clinical weakness attacks features in the HyperPP patient to a clinically meaningful degree. Consequently, the patient and treating physician decided to discontinue the salbutamol treatment. This study highlights the value of conducting N-of-1 trials in routine clinical practice to improve individual patient management, especially when level-1 evidence from RCTs is missing or when it is difficult to extrapolate group results to the individual patient.

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Full Citation: Stunnenberg, B. C., Merkus, E. C., Raaphorst, J., Saris, C. G., Groenewoud, H., Statland, J., ... & van der Wilt, G. J. (2021). N-of-1 trial of salbutamol in hyperkalaemic periodic paralysis. Journal of Neurology, Neurosurgery & Psychiatry, 92(12), 1352-1353.