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Zonegran or Zonisamide is one of the newer anti-epiletic drugs (AEDs).
It comes as a single sized tablet of 100 mg. The medication has a very
long half-life (measured in days, not hours) and therefore appropriate
for one time daily dosing. It is the only new AED that is indicated for
once daily dosing.
The medication has multiple mechanisms of action, the relative importance
of each to its anti-epileptic effect is not known. Mechanisms include
blocking sodium (Na+) channels, reducing voltage-dependent, transient
inward T-type calcium (Ca++) channels, increasing GABA release, blocking
potassium (K+) evoked glutamate-mediated synaptic excitation, and weakly
inhibiting carbonic anhydrase. It is considered effective in partial
onset seizures. It does
not appear to cause any bone marrow problems. Its incidence of liver
toxicity
is much lower than the older AEDs. It can cause renal stones. It is in
the sulfa family of drugs and therefore should not be used by patients
allergic to sulfa drugs. The medication should be discontinued in patients
who develop a rash. The medication does not interfere with birth control
pills. Its safety in pregnancy is not known. There are drug interactions
with other AEDs.
In open label trials, Zonegran® has been shown effective in reducing
the number of migraines.
In open label add on trials, Zonegran® has been shown to be effective
in some forms of neuropathic pain.
A very exciting recent placebo-controlled trial published in JAMA April
9, 2003 issue by Kishore Gadde, M.D. et. al., demonstrated a significant
weight loss in obese patients taking zonegran at a dose of at least 400
mg per day. At 32 weeks, the average patient demonstrated a 9.4% weight
loss. They lost on average 4 inches in the waist. Patients lost weight
in weeks 16 to 32 (although at a slower rate than weeks 0- 16 ) so the
final
weight loss is not known. This data adds to other data seen in epilepsy
patients which found weight loss as well. At least one study suggested
that females were more likely to lose weight than males.
Zonegran® has been used by psychiatrists as a mood stabilizing medication.
This topic is beyond the scope of this web site.
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