Prospective neurometric studies during the beginning of carbamazepine and phenytoin therapy

Antiepileptic drugs and peripheral nerve function: a multicenter screening investigation of 141 patients with chronic treatment. Collaborative Group for the Study of Epilepsy

One hundred forty-one adult patients treated for no less than 6 months with standard daily doses of the commonest antiepileptic drugs (AEDs) were recruited in five Italian centers and submitted to intensive clinical and electrophysiologic investigation to assess the effects of AEDs on peripheral nerves. Eighty percent of the patients were receiving monotherapy. Carbamazepine (CBZ) was the most common AED (51 cases), followed by phenytoin (PHT) (46), phenobarbital (PB) (42), and valproate (VPA) (25). Fifty-three percent of the patients had one or more symptoms of polyneuropathy (paresthesias being the most common complaint). The neurologic examination was abnormal in 32%. Electrophysiologic findings in two or more separate nerves were abnormal in 77 patients (54.6%); of these, 27 (19.1%) had abnormal neurologic findings and 21 (14.9%) also had symptoms of polyneuropathy. Sensory functions were most frequently impaired. Sural nerve biopsy was performed in 4 patients receiving monotherapy with CBZ, PHT, PB, and VPA. Except in patients receiving VPA (in whom no morphologic abnormalities were detected), mild predominantly axonal damage with secondary myelin changes was noted. A correlation was noted between polyneuropathy, age of the patient and, to a lesser extent, receipt of two or more AEDs.

Effect of acute doses of controlled-release carbamazepine on clinical, psychomotor, electrophysiological, and cognitive parameters of brain function

The neurotoxic effect of acute doses of carbamazepine controlled-release (CBZ-CR) divitabs (800, 1,200, and 1,600 mg) was assessed on clinical, psychomotor, electrophysiological, and cognitive parameters of brain function in 10 healthy volunteers in a double-blind, randomised, placebo-controlled, phase I study. Significant changes compared to placebo were demonstrated for the clinical scales, ataxia (AT), convergence of the near-point (CNP), peak saccadic velocity (PSV), critical flicker fusion (CFF), spectral analysis of the EEG, and brainstem auditory evoked potential (BAEP) tests. Digit repetition, digit symbol substitution, Sternberg memory scanning time, Sternberg choice reaction time, saccadic latency, and saccadic accuracy showed important negative findings. Significant clinical tolerance to side effects developed within 20 to 33 h after CBZ-CR dosage during a period in which the mean CBZ blood levels remained virtually unchanged. CBZ-CR, 800, 1,200, and 1,600 mg yielded low, medium, and high therapeutic blood levels, respectively, for +10 to +33 h after dosage without the development of severe clinical side effects.

Comparison of the effects of carbamazepine and oxcarbazepine on peripheral nerve conduction

Twenty-five epileptic outpatients were studied to assess possible effects of the first 6 months of treatment with carbamazepine or oxcarbazepine using serial peripheral nerve conduction measurements. Carbamazepine caused a small slowing effect on the motor conduction of the median nerve after 4 weeks of treatment, and the effect was correlated with the fasting serum concentration of the drug. Slowed motor conduction value of the median nerve was also observed after 6 months of treatment with carbamazepine. Oxcarbazepine did not cause any statistically significant slowing of nerve conduction.