pharmacopeia
GET
/api/v1/drug/zonisamide
2D structure
1,2-benzoxazol-3-ylmethanesulfonamide
SMILES C1=CC=C2C(=C1)C(=NO2)CS(=O)(=O)N
InChIKey UBQNRHZMVUUOMG-UHFFFAOYSA-N

Mechanism of action

Sourced from openFDA

The precise mechanism(s) by which zonisamide exerts its antiseizure effect is unknown. Zonisamide demonstrated anticonvulsant activity in several experimental models.

Carbonic AnhydraseP-Glycoprotein

Indications

Sourced from openFDA
  • Zonisamide capsules are indicated as adjunctive therapy in the treatment of partial seizures in adults with epilepsy.ICD-10: G40.909

Contraindications

Sourced from openFDA
  • Zonisamide capsules are contraindicated in patients who have demonstrated hypersensitivity to sulfonamides or zonisamide.contraindicated

Dosage & administration

Sourced from openFDA

Zonisamide capsules are recommended as adjunctive therapy for the treatment of partial seizures in adults. Safety and efficacy in pediatric patients below the age of 16 have not been established. Zonisamide capsules should be administered once or twice daily, using 25 mg, 50 mg or 100 mg capsules. Zonisamide capsules are given orally and can be taken with or without food. Capsules should be swallowed whole. Adults over Age 16 The prescriber should be aware that, because of the long half-life of zonisamide, up to two weeks may be required to achieve steady state levels upon reaching a stable dose or following dosage adjustment. Although the regimen described below is one that has been shown to be tolerated, the prescriber may wish to prolong the duration of treatment at the lower doses in order to fully assess the effects of zonisamide at steady state, noting that many of the side effects of zonisamide are more frequent at doses of 300 mg per day and above. Although there is some evidence of greater response at doses above 100-200 mg/day, the increase appears small and formal dose-response studies have not been conducted. The initial dose of zonisamide should be 100 mg daily. After two weeks, the dose may be increased to 200 mg/day for at least two weeks. It can be increased to 300 mg/day and 400 mg/day, with the dose stable for at least two weeks to achieve steady state at each level.

Warnings & precautions

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Potentially Fatal Reactions to Sulfonamides: Fatalities have occurred, although rarely, as a result of severe reactions to sulfonamides (zonisamide is a sulfonamide) including Stevens-Johnson syndrome, toxic epidermal necrolysis, fulminant hepatic necrosis, agranulocytosis, aplastic anemia, and other blood dyscrasias. Such reactions may occur when a sulfonamide is readministered irrespective of the route of administration. If signs of hypersensitivity or other serious reactions occur, discontinue zonisamide immediately. Specific experience with sulfonamide-type adverse reaction to zonisamide is described below. Serious Skin Reactions Consideration should be given to discontinuing zonisamide in patients who develop an otherwise unexplained rash. If the drug is not discontinued, patients should be observed frequently. Seven deaths from severe rash [i.e., Stevens-Johnson syndrome (SJS) and toxic epidermal necrolysis (TEN)] were reported in the first 11 years of marketing in Japan. All of the patients were receiving other drugs in addition to zonisamide. In post-marketing experience from Japan, a total of 49 cases of SJS or TEN have been reported, a reporting rate of 46 per million patient-years of exposure. Although this rate is greater than background, it is probably an underestimate of the true incidence because of under-reporting. There were no confirmed cases of SJS or TEN in the U.S., European, or Japanese development programs. In the U.S.

Adverse reactions

Sourced from openFDA

The most common adverse reactions with zonisamide (an incidence at least 4% greater than placebo) in controlled clinical trials and shown in descending order of frequency were somnolence, anorexia, dizziness, ataxia, agitation/irritability, and difficulty with memory and/or concentration. In controlled clinical trials, 12% of patients receiving zonisamide as adjunctive therapy discontinued due to an adverse reaction compared to 6% receiving placebo. Approximately 21% of the 1,336 patients with epilepsy who received zonisamide in clinical studies discontinued treatment because of an adverse reaction. The most common adverse reactions leading to discontinuation were somnolence, fatigue and/or ataxia (6%), anorexia (3%), difficulty concentrating (2%), difficulty with memory, mental slowing, nausea/vomiting (2%), and weight loss (1%). Many of these adverse reactions were dose-related (see WARNINGS and PRECAUTIONS ) . Adverse Reaction Incidence in Controlled Clinical Trials Table 4 lists adverse reactions that occurred in at least 2% of patients treated with zonisamide in controlled clinical trials that were numerically more common in the zonisamide group. In these studies, either zonisamide or placebo was added to the patient's current AED therapy.

Use in specific populations

Sourced from openFDA

Pregnancy: (see WARNINGS, Teratogenicity subsection): Zonisamide may cause serious adverse fetal effects, based on clinical and nonclinical data. Zonisamide was teratogenic in multiple animal species. Zonisamide treatment causes metabolic acidosis in humans. The effect of zonisamide induced metabolic acidosis has not been studied in pregnancy; however, metabolic acidosis in pregnancy (due to other causes) may be associated with decreased fetal growth, decreased fetal oxygenation, and fetal death, and may affect the fetus's ability to tolerate labor. Pregnant patients should be monitored for metabolic acidosis and treated as in the non-pregnant state (see WARNINGS, Metabolic Acidosis subsection). Newborns of mothers treated with zonisamide should be monitored for metabolic acidosis because of transfer of zonisamide to the fetus and possible occurrence of transient metabolic acidosis following birth. Transient metabolic acidosis has been reported in neonates born to mothers treated during pregnancy with a different carbonic anhydrase inhibitor. Zonisamide was teratogenic in mice, rats, and dogs and embryolethal in monkeys when administered during the period of organogenesis.

Pharmacokinetics

Sourced from openFDA
Metabolism
Absorption Following a 200-400 mg oral zonisamide dose, peak plasma concentrations (range: 2 mcg/mL to 5 mcg/mL) in normal volunteers occur within 2-6 hours. In the presence of food, the time to maximum concentration is delayed; occurring at 4-6 hours, but food has no effect on the bioavailability of zonisamide.

Overdosage

Sourced from openFDA

Human Experience Experience with zonisamide daily doses over 800 mg/day is limited. During zonisamide clinical development, three patients ingested unknown amounts of zonisamide as suicide attempts, and all three were hospitalized with CNS symptoms. One patient became comatose and developed bradycardia, hypotension, and respiratory depression; the zonisamide plasma level was 100.1 mcg/mL measured 31 hours post-ingestion. Zonisamide plasma levels fell with a half-life of 57 hours, and the patient became alert five days later. Management No specific antidotes for zonisamide overdosage are available. Following a suspected recent overdose, emesis should be induced or gastric lavage performed with the usual precautions to protect the airway. General supportive care is indicated, including frequent monitoring of vital signs and close observation. Zonisamide has a long half-life (see CLINICAL PHARMACOLOGY section ). Due to the low protein binding of zonisamide (40%), renal dialysis may be effective. The effectiveness of renal dialysis as a treatment of overdose has not been formally studied.

Approval history

Sourced from openFDA
  • Mar 27, 2000NDANDA020789Advanz Pharma
  • Dec 22, 2005ANDAANDA077645Aurobindo Pharma Ltd
  • Jan 30, 2006ANDAANDA077651Glenmark Pharms
  • Mar 17, 2006ANDAANDA077634Sun Pharm Inds (in)
  • May 31, 2006ANDAANDA077869Invagen Pharms
  • Oct 16, 2006ANDAANDA077625Zydus Lifesciences
  • Jan 26, 2021ANDAANDA214492Unichem
  • Jul 15, 2022NDANDA214273Azurity

FAERS reports

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Reference statistics only. FAERS reports are voluntarily submitted and are not incidence rates, safety signals, or causal evidence. Counts reflect reporting volume — how often a reaction was reported, not how often it occurs. For decision-grade use, consult openFDA and the FAERS Public Dashboard directly.
14,486 total reports matchedLatest report Share = reports listing the reaction ÷ total matched reports. Rows can sum to >100% because a single report often lists multiple reactions.
  1. 1Drug Ineffective1,66311%
  2. 2Seizure1,62711%
  3. 3Off Label Use9086.3%
  4. 4Fatigue7084.9%
  5. 5Somnolence6664.6%
  6. 6Convulsion6224.3%
  7. 7Dizziness5703.9%
  8. 8Nausea5643.9%
  9. 9Headache5513.8%
  10. 10Fall5073.5%
  11. 11Drug Interaction4703.2%
  12. 12Condition Aggravated4543.1%
  13. 13Vomiting4423.1%
  14. 14Diarrhoea4172.9%
  15. 15Epilepsy3872.7%

Literature

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

Clinical trials

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The 10 most recently updated of 87 ClinicalTrials.gov registrations naming Zonisamide as an intervention. Registration is not evidence of efficacy or safety — reference crosswalk only.

Frequently asked questions

How does Zonisamide work?
The precise mechanism(s) by which zonisamide exerts its antiseizure effect is unknown. Zonisamide demonstrated anticonvulsant activity in several experimental models.
What is Zonisamide used for?
According to FDA labeling, Zonisamide carries indications including: Zonisamide capsules are indicated as adjunctive therapy in the treatment of partial seizures in adults with epilepsy.. This is a reference summary of labeled uses, not medical advice or a treatment recommendation.
What class of drug is Zonisamide?
Zonisamide is classified as Other antiepileptics, Anti-epileptic Agent, Carbonic Anhydrase Inhibitors, P-Glycoprotein Inhibitors, Unknown Cellular or Molecular Interaction, Decreased Central Nervous System Disorganized Electrical Activity, Neurotransmitter & Neuromuscular Transmitter Activity Alteration.
What are the brand names for Zonisamide?
Zonisamide is marketed under brand names including Zonegran, Zonisade.
What are the contraindications for Zonisamide?
Zonisamide labeling lists contraindications including: Zonisamide capsules are contraindicated in patients who have demonstrated hypersensitivity to sulfonamides or zonisamide.. Always consult the full prescribing information and a clinician.
Note. Data for zonisamide is illustrative MVP content compiled from public sources. pharmacopeia is for educational and informational use only and is not a substitute for professional medical advice.

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