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An Urban Experience
Levetiracetam is the S-enantiomer of the ethyl analogue of piracetam that has broad-ranging, unique but incompletely understood mechanisms of action against seizures. Its main mechanism may be in decreasing the onset of a seizure through enhanced GABA activated
Cl- conductance. The pharmacodynamic effect is believed to outlive the known half-life of the drug. In dogs, this drug has a half-life is approximately 4-6
hours, is liver cytochrome P450 independent and is excreted unchanged by the kidneys. The dose range documented for dogs is estimated to be 5-25 mg/kg q 8-12hrs PO. Levetiracetam has been documented as the most well tolerated anti-epileptic drug in humans, with adverse reactions equal to that of placebo. Overall, this drug is proven to be a highly effective adjunctive therapy in humans to control seizures. In 2006, levetiracetam was approved in humans as the first of the newer anticonvulsive drugs for intravenous administration and has been trialed for its use with status epilepticus. It has been shown that it is an effective drug in people with
this condition and is well tolerated at high doses. Recent pharmacokinetic studies in dogs have demonstrated that IV administration of this drug is well tolerated
when administered as a bolus at 60 mg/kg and rapidly achieved suggested therapeutic levels. Clinical veterinary trials are underway for this drug.
Experimental animal work has indicated that NMDA glutamate receptor antagonists may be used to treat
the so called self-sustaining status epilepticus (SSSE). This type of status exists after approximately 10
minutes to 1 hour and may have a different underlying pathophysiology to that of the initial SE in that NMDA receptors may be over stimulated by excessive glutamate concentrations. Ketamine is a NMDA receptor antagonist which has been used in humans with refractory or SSSE and has been shown to be effective in a dog with SSSE.
Inhalational Anesthesia
Inhalational anesthetics have been recommended as a last resort in cases of resistant SE. The equipment and personnel necessary to administer inhalational anesthesia may not be readily available and can be cumbersome. Isoflurane, an inhalational general anesthetic agent, may be efficacious in the treatment of resistant SE. Not all of the volatile anesthetic agents have anti-epileptic potential, however; enflurane may actually increase seizure activity. Isoflurane does not undergo hepatic metabolism, has a rapid onset of action and has been extensively studied. Obviously, isoflurane therapy necessitates ventilation and intensive-care monitoring, and hypotension may occur during therapy.

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