Carbamazepine in trigeminal neuralgia: clinical effects in relation to plasma-concentration

Seven patients (mean age 60 years) with idiopathic trigeminal neuralgia previously treated with Carbamazepine(CBZ) were studied as in patients. One patient was examined twice. CBZ (Tegretol) was given twice daily in three different dose-levels to each patient, six days on each level. A single-blind technique was used. The doses were individually chosen with previous dose requirements as a basis. Plasma samples were taken immediately before the morning dose the three last days on each dose-level. CBZ and CBZ-10, 11-epoxide were analysed using liquid chromatography. All pain paroxysms were graded and registered by the patient and pain scores were calculated. The CBZ-doses given ranged from 200 to 1 400 mg/day, the mean being 733 mg/day. In six courses of treatment, patients experienced complete or almost complete pain relief, achieved at CBZ-plasma-concentrations of 24-43 mumol/l. Patients with high pain-scores at plasma-concentrations of 30 mumol/l did not benefit from further dose increase. Small adjustments of plasma-concentration otherwise resulted in pronounced changes in pain-score. Side-effects were not reported below 34 mumol/l. No conclusions could be drawn as to the possible clinical effect of CBZ-10,11-epoxide.