02319nas a2200205   4500008004100000022001400041245010200055210006900157260001200226300001300238490000700251520166900258653003101927653002901958653002701987653001402014100002102028700001802049856004602067       1978                        eng d  a0013-958000aAcute and chronic antiepileptic drug effect on the T complex interhemispheric latency difference.0 aAcute and chronic antiepileptic drug effect on the T complex int  c02/1978  a99–1070 v193 aAntiepileptic drugs may significantly affect brain function in the absence of overt toxicity or excessive serum drug levels. A clinically practical monitor of such effects would be of considerable value in clinical research and practice.

Auditory evoked responses were recorded from patients before and after initiation of antiepileptic drug therapy and from patients on therapy for at least 1 year. T complexes were isolated (Wolpaw and Penry, 1975), and Ta peak ipsilateral versus contralateral latency differences were determined.

In 13 patients beginning phenobarbital, more than half the postdrug determinations were significantly increased over the patients' predrug control values in the first 30 days and thereafter, and grossly abnormal values were frequent. In 10 patients beginning phenytoin, latency differences were similarly increased, although grossly abnormal values were less common. In 2 patients beginning clonazepam, 14 of 15 postdrug determinations were significantly increased, and five were grossly abnormal. In no patients were serum drug levels above the therapeutic ranges. In 40 patients chronically treated with phenobarbital or primidone, phenytoin, or a combination of phenytoin and phenobarbital or primidone, abnormal latency differences were obtained in 33, 36, and 29% of the determinations, respectively.

The Ta peak ipsilateral versus contralateral latency difference is an internally controlled correlate of higher level specific sensory function which is sensitive to acute and chronic therapy with phenobarbital, phenytoin, or clonazepam in therapeutic dosages. With further investigation, it may be of clinical use.10aAntiepileptic drug effects10aAuditory evoked response10aHemispheric difference10aT complex1 aWolpaw, Jonathan1 aPenry, J., K.  uhttp://www.ncbi.nlm.nih.gov/pubmed/624272