DECREASE IN ERYTHROCYTE PLASMA LITHIUM RATIO BY CONCURRENT ADMINISTRATION OF PSYCHOTROPIC-DRUGS AND LITHIUM IN MICE/

1. Previous studies paying attention to concurrent use of lithium (Li) with a neuroleptic were not done under constant and controlled condi tions. We were therefore encouraged to do a prospectively controlled s tudy, presuming constant relevant factors, on concomitant use of Li+ w ith neuroleptic as well as other psychotropic agents. 2. The effects o f concurrent administration of chlorpromazine, haloperidol, imipramine and carbamazepine with Li+ on the erythrocyte:plasma Li+ ratio and th e intraerythrocyte Li+ concentration were studied in mice by using a n ew, direct method of measuring erythrocyte Li+ concentration. 3. All o f the foregoing agents with the exception of carbamazepine were observ ed to significantly decrease the Li+ ratio. 4. Lack of any significant effect by carbamazepine on Li+ transport may be an indication of this drug's efficacy as a supplement in Li+ therapy of bipolar affective d isorders. 5. The decrease in Li+ ratio observed with chlorpromazine, h aloperidol and imipramine map be explained through the mechanism by wh ich these drugs stabilize the cell membrane and consequently affect Li + transport in erythrocytes. 6. Moreover, our study proves that, altho ugh the Li+-sodium countertransport mechanism does not exist in mice, the same interaction between Li+ and other psychotropic drugs is seen. It can be concluded that such interaction is not mediated through Li-sodium countertransport. 7. It is suggested that, with concurrent use of a psychotropic drug and Li+, the amount of intraerythrocyte Li+ co ncentration be measured, instead of relying on the plasma Li+ concentr ation alone. (C) 1998 Elsevier Science Inc.