Ethosuximide is indicated for the treatment of absence seizures. It specifically blocks the T-type calcium channels of the thalamic relay neurons. It actually reduces the low
threshold calcium currents, which result in decreased release of excitatory glutamate in the synaptic cleft. This interrupts the loop of excitation between thalamus and cortex.
Side effects are relatively mild and include lethargy, nausea, and anorexia. Hypersensitivity reactions and changes in blood cell counts are rare.
Ethosuximide is not effective for other types of epilepsy.
Which of the following is an unusual concentration dependent side effect of ethosuximide?