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OLE Study

KEVEYIS for PPP: long-term data from the 1-year, open-label extension study1

Study design1:

From the 9-week, double-blind phase of Study 1, 41 of 44 patients in the hypokalemic substudy (KEVEYIS, n=22) and 17 of 21 patients in the hyperkalemic substudy (KEVEYIS, n=9) moved into a 1-year, open-label extension (OLE) phase in which all participants received KEVEYIS.

Average attack rate per week for patients on KEVEYIS at weeks 54-611*

Started and stayed on KEVEYIS through both phases diagram
Crossed over from placebo to KEVEYIS in OLE diagram

AR=attack rate; IQR=interquartile range; Wk=week.

  • *During the 1-year, uncontrolled extension phase, outcomes assessed included attack rate, severity-weighted attack rate, total attack duration per week (from weeks 54-61), and changes from week 9 to 61 in measures of strength and lean body mass. Adverse events and other safety outcomes were also considered.
  • Of the 17 patients who were enrolled in the long-term extension of the hyperkalemic PP trial, data were excluded for 1 patient in the 52-week, uncontrolled extension phase, who was included in the 9-week phase, as this participant was randomized to acetazolamide (the acetazolamide arm of the trial had to be abandoned owing to poor recruitment).

Characterization of common adverse events in the double-blind and OLE studies

An ad hoc analysis was performed to characterize the time course, intensity, and outcomes of paresthesia and cognition-related AEs during 61 weeks of KEVEYIS treatment for PPP

Cognition-related AEs included cognitive disorder, disturbance in attention, and mental impairment during 61 weeks of treatment in Study 1.2

Paresthesia and cognition-related AEs—the onset typically occurred during the first 4 weeks of treatment with KEVEYIS2

  • 25 of 63 (39.7%) patients had ≥1 report of paresthesia, and 16 of 63 (25.4%) patients had ≥1 cognition-related event
  • All reports of paresthesia were considered mild or moderate in intensity
  • The majority (88%) of cognition-related events were mild to moderate in intensity

Reductions in dose were commonly associated with resolution of AEs2

  • 6 of 25 (24.0%) patients with paresthesia had a reduction in the dose of KEVEYIS, and paresthesia resolved in 5 of the 6 cases
  • 6 of 16 (37.5%) patients with cognition-related AEs had a reduction in the dose of KEVEYIS, and the cognition-related AE resolved in all 6 cases

AEs were not frequently associated with discontinuation from the study2

  • Of the 63 patients, 1 patient discontinued due to paresthesia and 4 patients discontinued due to cognition-related AEs
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KEVEYIS is indicated for the treatment of primary hyperkalemic periodic paralysis, primary hypokalemic periodic paralysis, and related variants.

Important Safety Information

  • Hypersensitivity to dichlorphenamide or other sulfonamides
  • Concomitant use of KEVEYIS and high-dose aspirin
  • Severe pulmonary disease, limiting compensation to metabolic acidosis caused by KEVEYIS
  • Hepatic insufficiency: KEVEYIS may aggravate hepatic encephalopathy
Warnings and Precautions

Hypersensitivity and Other Life-Threatening Reactions

  • Fatalities associated with the administration of sulfonamides have occurred because of adverse reactions including Stevens-Johnson syndrome, toxic epidermal necrolysis, fulminant hepatic necrosis, agranulocytosis, aplastic anemia, and other blood dyscrasias.
  • Pulmonary involvement can occur in isolation or as part of a systemic reaction.
  • Discontinue KEVEYIS at the first appearance of skin rash or any sign of immune-mediated or other life-threatening adverse reaction.

Concomitant Use of Aspirin or Other Salicylates

  • Carbonic anhydrous inhibitors, including KEVEYIS, can cause metabolic acidosis, which can increase the risk of salicylate toxicity.
  • Anorexia, tachypnea, lethargy, and coma have been reported with concomitant use of dichlorphenamide and high-dose aspirin.
  • Concomitant use of KEVEYIS and high-dose aspirin is contraindicated. Use with caution and carefully monitor in patients receiving low-dose aspirin.


  • KEVEYIS increases potassium excretion and can cause hypokalemia.
  • The risk of hypokalemia is greater when KEVEYIS is used in patients with conditions associated with hypokalemia (e.g., adrenocortical excess, renal tubular acidosis type 1 and 2), and in patients receiving other drugs that may cause hypokalemia (e.g., loop diuretics, thiazide diuretics, laxatives, antifungals, penicillin, and theophylline).
  • Baseline and periodic measurements of serum potassium are recommended.
  • If hypokalemia develops or persists, consider reducing the dose or discontinuing KEVEYIS and correction of potassium levels.

Metabolic Acidosis

  • KEVEYIS can cause hyperchloremic non-anion gap metabolic acidosis.
  • Concomitant use of KEVEYIS with other drugs that cause metabolic acidosis may increase the severity of acidosis.
  • Concomitant use of KEVEYIS in compensated patients with respiratory acidosis, such as in advanced lung diseases, may lead to respiratory decompensation.
  • Baseline and periodic measurements of serum bicarbonate during KEVEYIS treatment are recommended.
  • If metabolic acidosis develops or persists, consider reducing the dose or discontinuing KEVEYIS.


  • KEVEYIS increases the risk of falls; risk is greater in the elderly and with higher doses.
  • Consider dose reduction or discontinuation of KEVEYIS in patients who experience falls while treated with KEVEYIS.
Pregnancy and Lactation

Use during pregnancy only if the potential benefit justifies the potential risk to the fetus. It is not known in humans whether dichlorphenamide is excreted in human milk; exercise caution when administered to a nursing woman.

Adverse Reactions

The most common adverse reactions seen in clinical trials (incidence ≥ 10% and greater than placebo) include paresthesias, cognitive disorder, dysgeusia, and confusional state.


  1. Sansone VA, Burge J, McDermott MP, et al; for the Muscle Study Group. Randomized, placebo-controlled trials of dichlorphenamide in periodic paralysis. Neurology. 2016;86:1408-1416.
  2. Hanna MG, Cohen F, Griggs RC. Characterization of common adverse events in a phase 3, placebo-controlled, double-blind and open-label extension study of dichlorphenamide for primary periodic paralysis. Poster presented at: The Muscle Study Group (MSG) Annual Scientific Meeting: September 17-19, 2018; Oxford, UK.