There's a wide variety of medications used for Migraine, most of which are prescribed off-label. If Zonegran (zonisamide) has been prescribed for you, or if you and your doctor have been considering it, here's some information that should be helpful. 

Type of medication:

Zonisamide, brand name Zonegran, is in a class of medications called carbonic anhydrase inhibitor anticonvulsants. Zonegran also has sulfa properties in it and can be prescribed off-label for Migraine and headache prevention. Other medications in this class include Topamax and Diamox.

SPECIAL DRUG WARNING

Zonisamide can be used for the adjunctive treatment for partial epilepsy in adults and other disorders as determined by your doctor. The Food and Drug Administration (FDA) has determined that treatment with zonisamide can cause metabolic acidosis in some patients. Zonisamide is indicated as adjunctive therapy in the treatment of partial seizures in adults with epilepsy.

 

Metabolic acidosis is a disturbance in the body's acid-base balance that results in excessive acidity of the blood. Metabolic acidosis is diagnosed by laboratory tests measuring the serum bicarbonate level in the blood to determine the presence and severity of metabolic acidosis.  

 

Metabolic acidosis can result in hyperventilation, and non-specific symptoms such as fatigue and anorexia, or more severe symptoms including cardiac arrhythmias or stupor. Chronic metabolic acidosis can have adverse effects on the kidneys and on bones, and can retard growth in children. Patients with predisposing conditions or therapies, including renal disease, severe respiratory disorders, diarrhea, surgery, ketogenic diet, or certain other drugs may be at greater risk for developing metabolic acidosis following treatment with zonisamide. The risk of zonisamide-induced metabolic acidosis appears to be more frequent and severe in younger patients.     

 

The FDA recommends that healthcare professionals measure serum bicarbonate before starting treatment and periodically during treatment with zonisamide, even in the absence of symptoms. If metabolic acidosis develops and persists, consideration should be given to reducing the dose or discontinuing zonisamide (using dose tapering), and modifying the patient’s antiepileptic treatment as appropriate. If the decision is made to continue patients with metabolic acidosis on zonisamide, then alkali treatment should be considered. 

The FDA is working with the makers of zonisamide to revise the product labeling to reflect this new safety information.¹

Precautions:

• If you are allergic to zonisamide or sulfa medications, do not use this drug. 
• Some anticonvulsant medications may cause people to be irritable, agitated or show other abnormal behaviors. It may also cause you to become more depressed or have suicidal thought and tendencies. If you have any of these side effects, please tell your doctor right away.
• If you are depressed or have a history of depression, caution should be used when taking zonisamide.
• If you develop a skin rash while taking zonisamide, get in touch with your doctor right away.
• Metabolic acidosis may occur when taking zonisamide. This risk may be higher is children and people who have serious breathing issues, status epilepticus, people with kidney issues and those taking certain medications, having surgery and being on a ketogenic diet. It is important to contact your doctor right away if you have any breathing that is too fast, abnormal weakness or tiredness, fainting, loss of appetite or irregular heartbeat.
• Caution is advised when taking zonisamide if you have kidney problems or failure, or liver problems.
• The elderly population may be more sensitive to it effects and caution must be used when taking it.
• Effective birth control is a must for those women taking zonisamide.
• Tremendous caution must be utilized when using zonisamide in children under 16-years-old as the efficacy and safety is not totally understood. Children may be at an increased risk of low growth, kidney stones, increased risk of heat stroke and metabolic acidosis.  
• Do not stop this medication abruptly, even if you are feeling good, as you may have very unpleasant withdrawal symptoms that may include seizures. You may need to slowly taper off zonisamide.
• Please keep all regularly scheduled doctors visits while taking zonisamide, your doctor will need to check you to make sure you are tolerating it.
• Zonisamide may weaken your thinking and reaction time; care must be used when operating machinery, a car or anything that needs attentiveness.
• Do not take any other medication, prescription, over-the-counter medications and/or herbal supplements unless you have discussed them with your doctor.
• If you are having surgery including dental work, let the doctor who is performing the surgery know you are taking zonisamide.
• Zonisamide can cause and increase in drowsiness, dizziness and/or vision issues and alcohol and/or certain other medications may make them worse.
• Decreased sweating may occur when taking zonisamide, which can raise the risk of heat stroke, namely in children. Take care to drink plenty of water, especially during exercise and hot weather, and look for signs of decreased sweating. Treat any signs of decreased sweating by getting to a cooler spot. If signs of unexplained fever, headache, mood changes and dizziness occur get medical help right away.