LETTERS Interaction between trazodone and carbamazepineTO THE EDITOR: Trazodone is an antidepressant derived from triazolopyridine. We describe a case in which the therapeutic combination of trazodone and carbamazepine is associated with a distinct increase in the serum concentration and serum concentration/dose ratio of carbamazepine.Case Report. A 53-year-old white man weighing 79 kg was diagnosed with secondarily generalized partial epilepsy and depression. He took carbamazepine and diazepam 10 mg/d and began treatment with trazodone 100 mg/d. The initial carbamazepine dose was 600 mg/d and was increased three months later to 700 mg/d ( Table 1). The biochemical parameters indicated normal hepatic function.The data of the analytical tests made to monitor the carbamazepine concentrations by fluorescent polarization immunoassay (TDx, Abbott Laboratories) are shown in Table 1. Blood samples were extracted in the morning, between nine and 10 hours following the last carbamazepine dose. The time sequence of carbamazepine concentration/dose ratio changes (Table 1) indicated a concentration/ dose ratio ~0.8 before trazodone treatment and an increase in concentration/dose ratio at the last analytical check, two months after beginning trazodone treatment, without an explanation for the increase. The patient did not show signs or symptoms of carbamazepine toxicity when the carbamazepine concentration increased.

Model calculations are used to explore the effects of the kinetics of diffusion of dissolved organic compounds into and out of low-permeability porous materials and of the rate of solution of nonaqueous phase liquid (NAPL) droplets (into the aqueous phase) on the rate of cleanup of contaminated aquifers. Two models are presented: (1) the flushing of organic compounds initially distributed as NAPL droplets in a fracture in a porous rock aquifer, and (2) the removal of organic compounds initially present as NAPL in an aquifer containing low-permeability porous clay lenses. NAPL droplet size is found to be of much less importance than the spacing of the fractures in the porous rock in the first model or the thickness of the clay lenses in the second.