Abstract
Plasma levels of chlorpromazine (CPZ) and levomepromazine (LPZ) were measured in schizophrenic inpatients during concomitant administration at the same dosage level for each drug. A determination was simultaneously carried out using high-performance liquid chromatography, as reported in a previous paper. CPZ and LPZ levels in plasma showed the highest values at 10: 00 a. m. or 2: 00 p. m. ; the latter was always higher than the former. In patients receiving a daily dose of 200 mg of each drug, the CPZ and LPZ levels were also higher than those in patients receiving both drugs daily at a dose of 100 mg each. The correlation between plasma levels and the dosages of CPZ and LPZ has been studied in three patients receiving the drugs. The results revealed a decrease in CPZ level and an increase in LPZ level dring concurrent administration. On the other hand, CPZ tended to be excreted in urine more than did LPZ ; in addition, there seem to be pharmacokinetic interactions (inhibition of LPZ metabolism and activation of CPZ metabolism) between the two drugs, although various factors have considerable influence on clinical pharmacokinetics.
