Effect of dose increments on serum carbamazepine concentration in epileptic patients.

The effect of progressive dose increments on the steady-state serum concentration of carbamazepine has been investigated prospectively in 20 adult institutionalised epileptic patients receiving long term therapy with the drug. In all but 1 subject, a strong positive correlation between the serum carbamazepine concentration and the prescribed daily dose was found. The relationship appeared to be linear over the dosage range examined (600 to 1400mg in most patients). In some patients, a trend was observed for the extrapolated regression lines to yield positive y-axis intercepts. The latter were significantly different from zero in 3 patients. Although these findings suggest that the relationship between serum carbamazepine concentration and dose may be curvilinear over the lower range of doses, further studies are required to clarify this point.