Dichlorphenamide

Dichlorphenamide is a carbonic anhydrase inhibitor. However, the precise mechanism by which dichlorphenamide exerts its therapeutic effects in patients with primary periodic paralysis is unknown.

• Dichlorphenamide tablets are indicated for the treatment of primary hyperkalemic periodic paralysis, primary hypokalemic periodic paralysis, and related variants.

• Dichlorphenamide is contraindicated in the following circumstances: Hypersensitivity to dichlorphenamide or other sulfonamides [see Warnings and Precautions ( 5.1 )] Concomitant use of dichlorphenamide and high dose aspirin [see Warnings and Precautions ( 5.2 ) and Drug Interactions ( 7.1 )] Severe pulmonary disease, limiting compensation to metabolic acidosis caused by dichlorphenamide [see Warnings and Precautions ( 5.4 )] Hepatic insufficiency: dichlorphenamide may aggravate hepatic encephalopathy.contraindicated

• Initiate dosing at 50 mg by mouth once or twice daily ( 2.1 ) • Titrate up or down dose based on individual response ( 2.1 ) • The minimum recommended dosage is 50 mg daily, and the maximum recommended dosage is 200 mg daily ( 2.1 ) • Evaluate response to dichlorphenamide tablets after 2 months of treatment ( 2.2 ) 2.1 Dosage Information Initiate dosing at 50 mg by mouth once or twice daily. The dosage may be increased or decreased based on individual response, at weekly intervals (or sooner in case of adverse reaction). The minimum recommended total daily dosage is 50 mg, and the maximum recommended total daily dosage is 200 mg. 2.2 Monitoring to Assess Effectiveness Primary hyperkalemic periodic paralysis, primary hypokalemic periodic paralysis, and related variants are a heterogeneous group of conditions, for which the response to dichlorphenamide may vary. Therefore, prescribers should evaluate the patient's response to dichlorphenamide after 2 months of treatment to decide whether dichlorphenamide tablets should be continued. 2.3 Monitoring to Assess Safety Baseline and periodic measurements of serum potassium and sodium bicarbonate during dichlorphenamide treatment is recommended [see Warnings and Precautions ( 5.3 , 5.4 )] .

Hypersensitivity and Other Life-Threatening Reactions: discontinue dichlorphenamide at the first appearance of skin rash or any sign of immune-mediated or idiosyncratic adverse reaction ( 5.1 ) Hypokalemia: baseline and periodic measurements of serum potassium are recommended; if hypokalemia develops or persists, consider reducing the dose or discontinuing dichlorphenamide and correcting potassium levels ( 5.3 ) Metabolic acidosis: baseline and periodic measurements of serum bicarbonate are recommended; if metabolic acidosis develops or persists, consider reducing the dose or discontinuing dichlorphenamide ( 5.4 ) Falls: consider reducing the dose or discontinuing dichlorphenamide in patients who experience falls ( 5.5 ) 5.1 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. Dichlorphenamide should be discontinued at the first appearance of skin rash or any sign of immune-mediated or other life-threatening adverse reaction. 5.2 Concomitant Use of Aspirin or Other Salicylates Carbonic anhydrase inhibitors, including dichlorphenamide, can cause metabolic acidosis [see Warnings and Precautions ( 5.4 )] , which can increase the risk of salicylate toxicity.

The following serious adverse reactions are described elsewhere in labeling: Hypersensitivity and Other Life-Threatening Reactions [see Warnings and Precautions ( 5.1 )] Hypokalemia [see Warnings and Precautions ( 5.3 )] Metabolic Acidosis [see Warnings and Precautions ( 5.4 )] Falls [ see Warnings and Precautions ( 5.5 )] Most common adverse reactions (incidence at least 10% and greater than placebo) include paresthesias, cognitive disorder, dysgeusia, and confusional state ( 6.1 ) To report SUSPECTED ADVERSE REACTIONS, contact Rising Pharma Holdings, Inc. at 1-844-874-7464, or FDA at 1-800-FDA-1088 or www.fda.gov/medwatch. 6.1 Clinical Trials Experience Because clinical trials are conducted under widely varying conditions, adverse reaction rates observed in the clinical trials of a drug cannot be directly compared to rates in the clinical trials of another drug and may not reflect the rates observed in practice. In a 9-week randomized controlled trial in adults with hyperkalemic or hypokalemic periodic paralysis (Study 1), the most common adverse reactions in patients treated with dichlorphenamide, with rates greater than placebo, were paresthesia, cognitive disorder, dysgeusia, and confusional state. The mean dose of dichlorphenamide was 94 mg/day in patients with hypokalemic periodic paralysis and 82 mg/day in patients with hyperkalemic periodic paralysis. Table 1 lists the incidence of adverse reactions that occurred in ≥ 5% of patients treated with dichlorphenamide and more commonly than in patients treated with placebo in Study 1.

Pregnancy: Based on animal data, may cause fetal harm ( 8.1 ) 8.1 Pregnancy Risk Summary There are no adequate data on the developmental risk associated with the use of dichlorphenamide in pregnant women. A no-effect dose has not been established. Dichlorphenamide was teratogenic when administered orally to pregnant rats. The background risk of major birth defects and miscarriage for the indicated population is unknown. In the U.S. general population, the estimated background risk of major birth defects and miscarriage in clinically recognized pregnancies is 2% to 4%, and 15% to 20%, respectively. Clinical Considerations Fetal/Neonatal adverse reactions Dichlorphenamide treatment can cause metabolic acidosis [see Warnings and Precautions ( 5.4 )] . The effect of dichlorphenamide-induced metabolic acidosis has not been studied in pregnancy; however, metabolic acidosis in pregnancy (due to other causes) can cause decreased fetal growth, decreased fetal oxygenation, and fetal death, and may affect the fetus’ ability to tolerate labor. Pregnant patients should be monitored for metabolic acidosis and treated as in the nonpregnant state. Newborns of mothers treated with dichlorphenamide should be monitored for metabolic acidosis because of possible occurrence of transient metabolic acidosis following birth.

Metabolism

After single-dose administration in healthy subjects in fasted state, dichlorphenamide C max and AUC increased in a dose-proportional manner within the range of 25 mg to 400 mg (2 times the maximum recommended dose). The steady-state is expected to be achieved within 10 days of twice-daily dosing.

Symptoms of overdosage or toxicity may include drowsiness, anorexia, nausea, vomiting, dizziness, ataxia, tremor, and tinnitus. In the event of overdosage, induce emesis or perform gastric lavage. The electrolyte disturbances most likely to be encountered from overdosage are hypokalemia and hyperchloremic metabolic acidosis.

• Jul 22, 1958NDANDA011366Xeris
• Dec 29, 2022ANDAANDA215924Torrent
• Nov 18, 2025ANDAANDA218783Rising

1. 1Paraesthesia30119%
2. 2Fatigue22214%
3. 3Disease Recurrence17311%
4. 4Muscular Weakness1619.9%
5. 5Feeling Abnormal1579.7%
6. 6Wrong Technique In Product Usage Process1519.3%
7. 7Asthenia1328.1%
8. 8Confusional State1257.7%
9. 9Dizziness1126.9%
10. 10Nausea1126.9%
11. 11Headache996.1%
12. 12Dysgeusia945.8%
13. 13Blood Potassium Decreased935.7%
14. 14Condition Aggravated925.7%
15. 15Diarrhoea855.2%

Recent PubMed references pinned to Dichlorphenamide as a MeSH major topic. Citations link to pubmed.ncbi.nlm.nih.gov.

• Safety and efficacy of dichlorphenamide in patients with periodic paralysis: A systematic review and meta-analysis.
  Neuromuscular disorders : NMD · 2026 · Haider S, Siddiqui AD, Asad M, et al.
  PMID 41371188DOI 10.1016/j.nmd.2025.106300
• Dichlorphenamide for Refractory Hyperkalemic Periodic Paralysis.
  Journal of clinical neuromuscular disease · 2021 · Katyal N, Singla P, Idiculla PS, et al.
  PMID 34431807DOI 10.1097/CND.0000000000000382
• Long-term efficacy and safety of dichlorphenamide for treatment of primary periodic paralysis.
  Muscle & nerve · 2021 · Sansone VA, Johnson NE, Hanna MG, et al.
  PMID 34129236DOI 10.1002/mus.27354
• Marked reduction in paralytic attacks in a patient with Andersen-Tawil syndrome switched from acetazolamide to dichlorphenamide.
  Neuromuscular disorders : NMD · 2021 · Gupta A, Iyadurai S, Roggenbuck J, et al.
  PMID 34078557DOI 10.1016/j.nmd.2021.04.001
• Efficacy and Safety of Dichlorphenamide for Primary Periodic Paralysis in Adolescents Compared With Adults.
  Pediatric neurology · 2019 · Ciafaloni E, Cohen F, Griggs R, et al.
  PMID 31570296DOI 10.1016/j.pediatrneurol.2019.07.019
• Open-Label, Dose-Escalation, Phase 1 Study of Safety and Single and Multiple-Dose Pharmacokinetics of Dichlorphenamide in Healthy Volunteers.
  Clinical pharmacology in drug development · 2019 · Cohen F
  PMID 29762909DOI 10.1002/cpdd.464
• Dichlorphenamide (Keveyis) for periodic paralysis.
  The Medical letter on drugs and therapeutics · 2016
  PMID 27049510
• Dichlorphenamide: A Review in Primary Periodic Paralyses.
  Drugs · 2016 · Greig SL
  PMID 26941026DOI 10.1007/s40265-016-0559-2

The 2 most recently updated of 2 ClinicalTrials.gov registrations naming Dichlorphenamide as an intervention. Registration is not evidence of efficacy or safety — reference crosswalk only.

• Hyper- and Hypokalemic Periodic Paralysis Study
  Completed · Phase 3 · Interventional · 71 enrolled · University of Rochester
  NCT00494507updated 2017-06-14
• Phase III Randomized, Double-Blind, Placebo-Controlled Study of Dichlorphenamide for Periodic Paralyses and Associated Sodium Channel Disorders
  Completed · Phase 3 · Interventional · 64 enrolled · National Center for Research Resources (NCRR)
  NCT00004802updated 2005-06-24

Frequently asked questions

How does Dichlorphenamide work?

Dichlorphenamide is a carbonic anhydrase inhibitor. However, the precise mechanism by which dichlorphenamide exerts its therapeutic effects in patients with primary periodic paralysis is unknown.

What is Dichlorphenamide used for?

According to FDA labeling, Dichlorphenamide carries indications including: Dichlorphenamide tablets are indicated for the treatment of primary hyperkalemic periodic paralysis, primary hypokalemic periodic paralysis, and related variants.. This is a reference summary of labeled uses, not medical advice or a treatment recommendation.

What class of drug is Dichlorphenamide?

Dichlorphenamide is classified as Carbonic anhydrase inhibitors, Carbonic Anhydrase Inhibitor, Carbonic Anhydrase Inhibitors, Decreased Adrenocorticotropic Hormone Secretion, Decreased Intraocular Aqueous Secretion, Increased Renal HCO3- Excretion, Increased Renal K+ Excretion, Increased Renal Na+ Excretion.

What are the brand names for Dichlorphenamide?

Dichlorphenamide is marketed under brand names including Keveyis, Ormalvi.

What are the contraindications for Dichlorphenamide?

Dichlorphenamide labeling lists contraindications including: Dichlorphenamide is contraindicated in the following circumstances: Hypersensitivity to dichlorphenamide or other sulfonamides [see Warnings and Precautions ( 5.1 )] Concomitant use of dichlorphenamide and high dose aspirin [see Warnings and Precautions ( 5.2 ) and Drug Interactions ( 7.1 )] Severe pulmonary disease, limiting compensation to metabolic acidosis caused by dichlorphenamide [see Warnings and Precautions ( 5.4 )] Hepatic insufficiency: dichlorphenamide may aggravate hepatic encephalopathy.. Always consult the full prescribing information and a clinician.