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Phenytoin, Phenobarbital, and Ethosuximide and Calcium Flux in Isolated Presynaptic Endings

Richard S. Sohn, MD; James A. Ferrendelli, MD

Arch Neurol. 1976;33(9):626-629.

Abstract
• Phenytoin, phenobarbital, ethosuximide, and procaine hydrochloride were evaluated for their ability to inhibit C^a flux into isolated presynaptic endings (synaptosomes) prepared from rabbit neocortex. Calcium influx produced by depolarizing concentrations (69 mM) of K⁺ was inhibited 7% to 63% by phenytoin, phenobarbital, or procaine, whereas ethosuximide was ineffective. Decreased Ca²⁺ influx was observed with as little as 0.08 mM phenytoin and 0.04 mM phenobarbital. In contrast, 4 mM procaine was needed to produce an effect. These results lead to the conclusion that ability to produce membrane stabilization is not a property of all anticonvulsant drugs; however, this property may be essential for the action of drugs effective in the treatment of major seizures.

Author Affiliations
From the departments of pharmacology and of neurology and neurological surgery, Washington University School of Medicine, St Louis.

Footnotes
Accepted for publication Oct 30, 1975.

Reprint requests to Department of Neurology and Neurological Surgery, Washington University School of Medicine, 660 S Euclid Ave, St Louis, MO 63110 (Dr Ferrendelli).

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