Ormalvi

Dichlorphenamide · Tablet · Oral

Prescription (Rx) Carbonic Anhydrase Inhibitor

Uses

1 INDICATIONS AND USAGE ORMALVI is indicated for the treatment of primary hyperkalemic periodic paralysis, primary hypokalemic periodic paralysis, and related variants. ORMALVI is an oral carbonic anhydrase inhibitor indicated for the treatment of primary hyperkalemic periodic paralysis, primary hypokalemic periodic paralysis, and related variants ( 1 )

Dosage and administration

• 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 ORMALVI 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 ORMALVI may vary. Therefore, prescribers should evaluate the patient's response to ORMALVI after 2 months of treatment to decide whether ORMALVI should be continued. 2.3 Monitoring to Assess Safety Baseline and periodic measurements of serum potassium and sodium bicarbonate during ORMALVI treatment is recommended [see Warnings and Precautions ( 5.3 , 5.4 )] .

Dosage forms and strengths

White to off-white, round shaped, flat faced beveled edged tablet, scored on one side, engraved with ‘ZD’ above the score and ‘50’ below the score, the other side is plain. Tablets: 50 mg ( 3 )

Contraindications

4 CONTRAINDICATIONS ORMALVI is contraindicated in the following circumstances: Hypersensitivity to dichlorphenamide or other sulfonamides [see Warnings and Precautions ( 5.1 )] Concomitant use of ORMALVI 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 ORMALVI [see Warnings and Precautions ( 5.4 )] Hepatic insufficiency: ORMALVI may aggravate hepatic encephalopathy. Hepatic insufficiency ( 4 ) Severe pulmonary obstruction ( 4 ) Hypersensitivity to dichlorphenamide or other sulfonamides ( 4 ) Concomitant use with high dose aspirin ( 4 )

Warnings and precautions

Hypersensitivity and Other Life-Threatening Reactions: discontinue ORMALVI 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 ORMALVI 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 ORMALVI ( 5.4 ) Falls: consider reducing the dose or discontinuing ORMALVI 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. ORMALVI 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 ORMALVI, can cause metabolic acidosis [see Warnings and Precautions ( 5.4 )] , 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. Therefore, the concomitant use of ORMALVI and high-dose aspirin is contraindicated. Patients with concomitant use of ORMALVI and low-dose aspirin should be carefully monitored. 5.3 Hypokalemia ORMALVI increases potassium excretion and can cause hypokalemia. The risk of hypokalemia is greater when ORMALVI 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 [see Drug Interactions ( 7.3 )]. Baseline and periodic measurements of serum potassium during ORMALVI treatment is recommended. If hypokalemia develops or persists, consideration should be given to reducing the dose or discontinuing ORMALVI and correction of potassium levels. 5.4 Metabolic Acidosis ORMALVI can cause hyperchloremic non-anion gap metabolic acidosis. Concomitant use of ORMALVI with other drugs that cause metabolic acidosis may increase the severity of acidosis. Concomitant use of ORMALVI 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 ORMALVI treatment are recommended. If metabolic acidosis develops or persists, consideration should be given to reducing the dose or discontinuing ORMALVI [see Drug Interactions ( 7.4) ]. 5.5 Falls ORMALVI increases the risk of falls. The risk of falls is greater in the elderly and with higher doses of ORMALVI. Consider dose reduction or discontinuation of ORMALVI in patients who experience falls while treated with ORMALVI.

Side effects

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 Cycle Pharmaceuticals Ltd at 1-857-437-3969 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. Table 1: Adverse Reactions in Patients Treated with Dichlorphenamide with Incidence 5% and more common than in Patients Treated with Placebo in Study 1 Adverse Reaction Dichlorphenamide N = 36 (%) Placebo N = 29 (%) Nervous system disorders Paresthesia 44 14 Cognitive disorder 1 14 7 Dysgeusia 14 0 Confusional state 11 0 Headache 8 7 Hypoesthesia 8 0 Lethargy 8 0 Dizziness 6 0 Gastrointestinal disorders Diarrhea 6 3 Nausea 6 0 General disorders and administration site conditions Fatigue 8 0 Malaise 6 0 Investigations Weight decreased 6 0 Musculoskeletal and connective tissue disorders Muscle spasms 8 0 Arthralgia 6 3 Muscle twitching 6 0 Respiratory Dyspnea 6 0 Pharyngolaryngeal pain 6 0 Skin Rash 8 0 Pruritus 6 0 1 Cognitive disorder combined cases with the preferred terms of cognitive disorder, disturbance in attention, and mental impairment. 6.2 Postmarketing Experience Adverse reactions have been identified during postapproval use of dichlorphenamide. Because these reactions are reported voluntarily from a population of uncertain size, it is not always possible to reliably estimate their frequency or establish a causal relationship to drug exposure. The following are adverse reactions which have been reported during postapproval use of dichlorphenamide and were serious or are not reported in the previous section of labeling [see Clinical Trials Experience ( 6.1 ) ] : amnesia, cardiac failure, condition aggravated, convulsion, hallucination, nephrolithiasis, pancytopenia, psychotic disorder, renal tubular necrosis, stupor, syncope, tremor.

Drug interactions

Aspirin: anorexia, tachypnea, lethargy, and coma have been reported with concomitant use of dichlorphenamide and high-dose aspirin. The concomitant use of ORMALVI and high-dose aspirin is contraindicated. ORMALVI should be used with caution in patients receiving lower doses of aspirin ( 4 , 5.2 , 7.1 ) 7.1 Aspirin and Other Salicylates Carbonic anhydrase inhibitors, including ORMALVI, can cause metabolic acidosis [see Warning and Precautions ( 5.2 , 5.4 )] , 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. Therefore, concomitant use of ORMALVI and high-dose aspirin is contraindicated. Patients with concomitant use of ORMALVI and low-dose aspirin should be carefully monitored [see Contraindications ( 4 ) and Warnings and Precautions ( 5.2 )]. 7.2 Drugs that are Substrates of Organic Anion Transporter1 (OAT1) In vitro , dichlorphenamide is an inhibitor of OAT1 transporters. The concomitant administration of ORMALVI may increase the plasma exposures of OAT1 substrates. Use of ORMALVI with drugs that are sensitive to OAT1 inhibition (e.g., methotrexate, famotidine, oseltamivir) is not recommended [see Clinical Pharmacology ( 12.3 )]. 7.3 Drugs that Cause Hypokalemia The risk of hypokalemia is greater with coadministration of ORMALVI and other drugs that can cause hypokalemia (e.g., loop diuretics, thiazide diuretics, laxatives, antifungals, penicillins, and theophylline) [see Warnings and Precautions ( 5.3 )]. 7.4 Drugs that Cause Metabolic Acidosis Coadministration of ORMALVI and other drugs that can cause metabolic acidosis may increase the severity of the acidosis [see Warnings and Precautions ( 5.4 )]. 7.5 Drugs that are Inhibitors of OAT1 or OAT3 An in vitro transporter study indicated that dichlorphenamide is a substrate of human transporters OAT1 and OAT3 [see Clinical Pharmacology ( 12.3 )] . Therefore, signs of dichlorphenamide toxicity should be monitored when administered with OAT1 or OAT3 inhibitors.

Use in specific populations

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 ORMALVI 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 ORMALVI 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 ORMALVI should be monitored for metabolic acidosis because of possible occurrence of transient metabolic acidosis following birth. Labor or Delivery Although the effect of ORMALVI 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. Data Animal Data Teratogenic effects (fetal limb reduction defects) were reported following oral administration of dichlorphenamide to pregnant rats during organogenesis at 350 mg/kg, or 17 times the maximum recommended human dose (200 mg/day) on a body surface area (mg/m 2 ) basis. A no-effect dose for adverse effects on embryofetal development has not been established. 8.2 Lactation Risk Summary There are no data on the presence of dichlorphenamide in human milk, the effects on the breastfed infant, or the effects on milk production. The developmental and health benefits of breastfeeding should be considered along with the mother’s clinical need for ORMALVI and any potential adverse effects on the breastfed infant from ORMALVI or from the underlying maternal condition. 8.4 Pediatric Use Safety and effectiveness of ORMALVI in pediatric patients have not been established. 8.5 Geriatric Use The risk of falls and of metabolic acidosis are greater in elderly patients [see Warnings and Precautions ( 5.4 , 5.5 )].

Pregnancy

8.1 Pregnancy Risk Summary There are no adequate data on the developmental risk associated with the use of ORMALVI 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 ORMALVI 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 ORMALVI should be monitored for metabolic acidosis because of possible occurrence of transient metabolic acidosis following birth. Labor or Delivery Although the effect of ORMALVI 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. Data Animal Data Teratogenic effects (fetal limb reduction defects) were reported following oral administration of dichlorphenamide to pregnant rats during organogenesis at 350 mg/kg, or 17 times the maximum recommended human dose (200 mg/day) on a body surface area (mg/m 2 ) basis. A no-effect dose for adverse effects on embryofetal development has not been established.

Pediatric use

8.4 Pediatric Use Safety and effectiveness of ORMALVI in pediatric patients have not been established.

Geriatric use

8.5 Geriatric Use The risk of falls and of metabolic acidosis are greater in elderly patients [see Warnings and Precautions ( 5.4 , 5.5 )].

Overdosage

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.

Description

11 DESCRIPTION ORMALVI tablets, USP contain dichlorphenamide, an oral carbonic anhydrase inhibitor. Dichlorphenamide, USP a dichlorinated benzenedisulfonamide, is known chemically as 4, 5–dichloro-1,3-benzenedisulfonamide. Its empirical formula is C 6 H 6 Cl 2 N 2 O 4 S 2 and its structural formula is: Dichlorphenamide USP is a white or practically white, crystalline powder with a molecular weight of 305.16. It is very slightly soluble in water but soluble in dilute solutions of alkali carbonate and hydroxide. ORMALVI (dichlorphenamide) tablets, USP are supplied as tablets, for oral administration, each containing 50 mg dichlorphenamide. Inactive ingredients are lactose monohydrate, partially pregelatinized starch and magnesium stearate. FDA approved dissolution test specifications differ from USP. image description

Mechanism of action

12.1 Mechanism of Action 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.

How supplied

Each ORMALVI (dichlorphenamide) tablet USP, 50 mg is white to off-white, round shaped, flat faced beveled edged tablet, scored on one side, engraved with ‘ZD’ above the score and ‘50’ below the score, the other side is plain. ORMALVI (dichlorphenamide) tablets are supplied as follows: Bottles of 100 NDC 70709-085-10 Store at 20° to 25°C (68° to 77°F); excursions permitted to 15° to 30°C (59° to 86°F) [See USP Controlled Room Temperature].

Patient information

Worsening of Symptoms Advise patients to notify their physician if they experience acute worsening of symptoms of periodic paralysis. Hypersensitivity and Other Life-threatening Reactions Inform patients that hypersensitivity and immune mediated reactions can occur with ORMALVI and could be fatal. Advise patients to discontinue ORMALVI and notify their healthcare provider immediately if they develop a rash or signs and symptoms of anaphylaxis or other life-threatening reactions [see Warnings and Precautions ( 5.1 )]. Drug Interactions Instruct patients to notify their healthcare provider of all of the drugs and over-the-counter medications that they take and to not take aspirin or other salicylates without first discussing with their healthcare provider [see Drug Interactions ( 7.1 , 7.2 , 7.3 , 7.4 )]. Metabolic Acidosis Instruct patients to contact their healthcare provider immediately if they develop possible manifestations of metabolic acidosis (e.g., fast breathing, fatigue/tiredness, loss of appetite, or irregular heartbeat or palpitations) [see Warnings and Precautions ( 5.4 )]. Falls Inform patients that ORMALVI can increase their risk of falls [see Warnings and Precautions ( 5.5 )]. Cognitive Impairment Advise patients to notify their healthcare provider if they experience symptoms of cognitive impairment including confusion and memory lapse [see Adverse Reactions ( 6.1 )]. Driving and Operating Machinery ORMALVI may cause drowsiness/fatigue in some patients [see Adverse Reactions ( 6.1 )]. Caution patients on the potential for impaired ability to drive and operate machinery.

Label text from the FDA structured product label by Cycle Pharmaceuticals Ltd. (revised Jul 15, 2025). Long sections are shortened; the complete label is on DailyMed.

Active ingredients

Dichlorphenamide in 1 product

Ormalvi NDC products (1)

NDC	Strength & form	Labeler	Type
70709-085	Dichlorphenamide 50 mg/1 Tablet	Cycle Pharmaceuticals Ltd.	ANDA

Frequently asked questions

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Who makes Ormalvi?

Ormalvi is listed by 1 labeler in the FDA NDC directory, including Cycle Pharmaceuticals Ltd..