Dichlorphenamide

Dichlorphenamide is a prescription medication indicated for primary hyperkalemic periodic paralysis, primary hypokalemic periodic paralysis, and related variants.

• Dichlorphenamide is available under the following different brand names: Keveyis and Ormalvi.

Common side effects of Dichlorphenamide include:

• tingling or pricking sensations
• cognitive disorder
• changes in the sense of taste
• confusion
• headache
• numbness
• lethargy
• dizziness
• diarrhea
• nausea
• fatigue
• malaise
• weight loss
• muscle spasms or twitching
• joint pain
• indigestion
• throat pain
• rash
• itching

Serious side effects of Dichlorphenamide include:

• hives
• difficulty breathing
• swelling of the face, lips, tongue, or throat
• fever
• sore throat
• burning eyes
• skin pain
• red or purple skin rash with blistering and peeling
• skin rash 
• accidental fall
• worsening of paralysis symptoms
• leg cramps
• constipation
• irregular heartbeats
• fluttering in the chest
• increased thirst
• increased urination
• numbness or tingling
• muscle weakness or limp feeling
• tiredness
• loss of appetite
• trouble thinking
• shortness of breath

Rare side effects of Dichlorphenamide include:

• none 

Seek medical care or call 911 at once if you have the following serious side effects:

• Severe headache, confusion, slurred speech, arm or leg weakness, trouble walking, coordination loss, unsteady, very stiff muscles, high fever, profuse sweating, or tremors.
• Serious eye symptoms such as sudden vision loss, blurred vision, tunnel vision, eye pain or swelling, or seeing halos around lights.
• Serious heart symptoms include fast, irregular, or pounding heartbeats; fluttering in the chest; shortness of breath; sudden dizziness, lightheadedness, or passing out.

This is not a complete list of side effects and other serious side effects or health problems that may occur because of the use of this drug. Call your doctor for medical advice about serious side effects or adverse reactions. You may report side effects or health problems to FDA at 1-800-FDA-1088.

Adult dosage

Tablet

• 50 mg

Periodic paralysis

Adult and geriatric dosage

• 50 mg orally once a day or every 12 hours initially; increase or decrease at weekly intervals according to individual response; not to exceed 200 mg/day
• Evaluate response after 2 months of treatment to decide drug should be continued

Dosage Considerations – Should be Given as Follows: 

• See “Dosages”

If your medical doctor is using this medicine to treat your pain, your doctor or pharmacist may already be aware of any possible drug interactions and may be monitoring you for them. Do not start, stop, or change the dosage of any medicine before checking with your doctor, health care provider, or pharmacist first.

• Dichlorphenamide has severe interactions with the following drugs:
  • aminosalicylic acid
  • aspirin
  • aspirin rectal
  • bismuth subsalicylate
  • choline magnesium trisalicylate
  • magnesium salicylate
  • salsalate
• Dichlorphenamide has serious interactions with the following drugs:
  • metoclopramide intranasal
  • ropeginterferon alfa 2b
  • zuranolone
• Dichlorphenamide has moderate interactions with at least 260 other drugs
• Dichlorphenamide has minor interactions with no other drugs

This information does not contain all possible interactions or adverse effects. Visit the RxList Drug Interaction Checker for any drug interactions. Therefore, before using this product, tell your doctor or pharmacist about all the products you use. Keep a list of all your medications with you and share this information with your doctor and pharmacist. Check with your healthcare professional or doctor for additional medical advice, health questions, or concerns.

Contraindications

• Hypersensitivity to Dichlorphenamide or other sulfonamides
• Coadministration with high-dose aspirin
• Severe pulmonary disease, limiting compensation to metabolic acidosis caused by Dichlorphenamide
• Hepatic insufficiency: Dichlorphenamide may aggravate hepatic encephalopathy

Effects of drug abuse

• None

Short-Term Effects

• See “What Are Side Effects Associated with Using Dichlorphenamide?”

Long-Term Effects

• See “What Are Side Effects Associated with Using Dichlorphenamide?”

Cautions

• Fatalities associated with sulfonamides reported; hypersensitivity, anaphylaxis, and idiosyncratic reactions reported and may include Stevens-Johnson syndrome, toxic epidermal necrolysis, fulminant hepatic necrosis, agranulocytosis, aplastic anemia, and other blood dyscrasias; pulmonary symptoms may occur in isolation or as part of a systemic reaction; discontinue at first sign of rash
• Dichlorphenamide increases potassium excretion and may cause hypokalemia reported; monitor potassium levels periodically; risk is greater when used with conditions associated with hypokalemia (eg, adrenocortical insufficiency, hyperchloremic metabolic acidosis, respiratory acidosis) and in patients receiving other drugs that may cause hypokalemia; if hypokalemia develops or persists, consider dose reduction or discontinuation of the drug, and correct serum potassium
• Can cause hyperchloremic non-anion gap metabolic acidosis; coadministration with other drugs that cause metabolic acidosis may increase the severity; measure bicarbonate at baseline and then periodically; if metabolic acidosis develops or persists, consider reducing the dose or discontinuing the drug
• Increased risk of falls; risk is greater in elderly patients and with higher doses
• Drug interaction overview
• Aspirin and other salicylates
• Carbonic anhydrase inhibitors, including Dichlorphenamide, can cause metabolic acidosis, which may increase salicylate toxicity
• Contraindicated with high-dose aspirin owing to risk of anorexia, tachypnea, lethargy, and coma
• Monitor carefully if coadministered with low-dose aspirin
• OAT1 substrates
  • Dichlorphenamide is an inhibitor of OAT1 transporters in vitro
  • Coadministration may increase plasma exposure of OAT1 substrates
  • Use with sensitive OAT1 substrates (methotrexate, famotidine, oseltamivir) is not recommended
• OAT1/3 inhibitors
  • Dichlorphenamide is a substrate of human transporters OAT1 and OAT3
  • Monitor for signs of Dichlorphenamide toxicity if coadministered with OAT1 or OAT3 inhibitors
• Drug-induced hypokalemia
  • Hypokalemia risk increases if coadministered with other drugs that decrease serum potassium (eg, loop diuretics, thiazide diuretics, laxatives, antifungals, penicillin, theophylline)
• Drug-induced metabolic acidosis
  • Coadministration with other drugs that cause metabolic acidosis may increase acidosis severity

Pregnancy and Lactation

• Data are not available on the developmental risk associated with the use in pregnant women
• Clinical considerations
  • Treatment can cause metabolic acidosis
  • 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
  • Monitor pregnant women for metabolic acidosis and treat as in the nonpregnant state
  • Monitor newborns of mothers treated with Dichlorphenamide for metabolic acidosis because of the possible occurrence of transient metabolic acidosis following birth
• Labor or delivery
  • Although the effect on labor and delivery in humans has not been established, the development of Dichlorphenamide-induced metabolic acidosis in the mother and/or in the fetus might affect the fetus’ ability to tolerate labor
• Lactation
  • Unknown if distributed in human breast milk
  • Consider the developmental and health benefits of breastfeeding along with the mother’s clinical need for the drug and any potential adverse effects on the breastfed infant from the drug or the underlying maternal condition