Zonisamide is sold under the brand name "Zonegran".
Brand names also include Exegran, among others.
Zonisamide is approved for use in certain kinds of epilepsy in adult patients. It is not approved for use in Bipolar Disorder, but because of its tendency to cause weight loss it is being used in some cases as a third line agent.
Zonisamide appears to have several mechanisms of action that may be relevant to use in psychiatry. It affects certain sodium channels and calcium channels. It also enhances serotonin and dopamine function and blocks certain enzyme systems further to enhance dopamine function.
The support for the use of zonisamide in psychiatry is limited. However, it is unusual for a medication to be associated with weight loss, and that in addition to the effectiveness of other antiepileptics in psychiatry has led to its use, particular as an adjunctive treatment in Bipolar Disorder. It may also be helpful in Bulimia Nervosa and migraine prophylaxis, but, again, the support here is limited and its use is based on its similarity to topiramate, which has good support in the treatment of Bulimia Nervosa and migraines.
Zonisamide is metabolized to inactive compounds but much of zonisamide is eliminated unchanged via the kidneys.
Adverse effects can include Stevens Johnson syndrome, as do many other antiepileptics. There are also case reports of possible aplastic anemia and agranulocytosis (possibly fatal; too rare to merit routine monitoring) and liver damage (again, too rare to merit routine monitoring of hepatic function). Finally, in children there are reports of reduction in sweating and consequent “heat stroke”.
Less serious side effects can include sedation, cognitive impairment, headaches, difficulty walking, stomach distress, nausea and vomiting, and kidney stones.
Zonisamide has not been firmly associated with birth defects, but the association of so many medications in the same class with birth defects suggests a cautious approach to the use of zonisamide in pregnancy. If you think you may be pregnant call the office for an urgent appointment to discuss the medication options in pregnancy. Dr. Hoopes suggests that all women of childbearing age taking zonisamide take a prenatal vitamin as well.
If you miss a dose of zonisamide do not add it to the next dose. It is important to take zonisamide regularly as it is prescribed.
