Controlled evaluation of a supplementary dose of carbamazepine on psychomotor function in epileptic patients

The effect of an additional dose of 400 mg carbamazepine (CBZ) on a series of simple psychomotor tests was investigated in 8 patients with epilepsy receiving chronic CBZ monotherapy in a balanced randomised double-blind placebo controlled cross-over study. Psychomotor testing and blood sampling for total and free CBZ and CBZ 10,11 epoxide (CBZ-E) concentrations were performed at 10, 12, 14, 16 and 18 h after the extra dose which was administered at 23.00 h on the previous evening. The CBZ increment produced significant impairment of choice reaction recognition time from 10-16 h after the dose total choice reaction time at 12 h card sorting at 12 h sedation scoring at 12 h. No significant effect on critical flicker fusion threshold, finger tapping or simple memory testing was noted. No patient reported increased side-effects in the placebo phase while 5 noted new symptoms likely to be attributable to the additional CBZ. Areas under the concentration-time curves from 10-18 h were higher following CBZ than placebo for total and free CBZ and CBZ-E concentrations. This study has demonstrated decrements in performance of a series of simple psychomotor tests in epileptic patients receiving a supplemental CBZ dose. Patients with epilepsy who require high CBZ concentrations for optimal control of seizures may be at risk of concurrent impairment of psychomotor function. Simple objective measures of performance may help in assessing the benefit-risk ratio.