• Blocks the carbonic anhydrase enzyme, which is responsible for converting CO2 and H2O
to bicarbonate. This increases excretion of sodium, potassium,
bicarbonate and water, producing alkaline diuresis. In epilepsy,
decreases excessive neuronal
discharge in CNS due either to inhibition of carbonic anhydrase or
slight degree of acidosis.
It also reduces production of CSF
and aqueous humor
How Long Until It Works
• Seizures - by 2-3 weeks
• IIH - maximum benefit in 4-6 weeks
If It Works
• Seizures - goal is the remission of seizures. Continue as long as effective and well-tolerated. Consider tapering and slowly
stopping after 2 years seizure-free, depending on the type of epilepsy
• IIH - monitor visual fields and papilledema and symptoms such as visual obscurations and headache
If It Doesn't Work
Increase to highest tolerated dose
• Seizures - consider changing to another agent, adding a second agent or referral for epilepsy surgery evaluation. When adding
a second agent keep in mind the drug interactions that can occur
• IIH
- eliminate symptomatic causes such as drugs or toxins, encourage
weight loss if patient is obese, consider loop diuretics
or topiramate. Lumbar puncture often
provides short-term relief of symptoms. For visual loss, optic nerve
defenestration or
CSF shunting (lumboperitoneal or
ventriculoperitoneal) may be needed
Best Augmenting Combos for Partial Response or Treatment-Resistance
• Epilepsy
- acetazolamide itself is usually an augmenting agent. Relatively few
interactions with other AEDs. Topiramate and
zonisamide have similar mechanisms
of action, so acetazolamide is not usually combined with these agents
• IIH - furosemide and topiramate may be helpful. Combine with caution due to risk of kidney stone formation
Tests
• Obtain a CBC when starting drug and during therapy. Check bicarbonate, potassium, and sodium levels if symptoms of metabolic
acidosis develop