Of 33 chronically psychotic patients in a state hospital, 17 received
carbamazepine, 13 received carbamazepine and lithium, and three received
carbamazepine and then the combination. There was a significant difference
in serum sodium level between the patients receiving carbamazepine alone
(mean +/- SD = 138.4 +/- 4.3 meq/liter) and those also receiving lithium
(141.8 +/- 1.6 meq/liter). (A similar difference was seen for the patients
who received the two treatments serially.) Age, sex, diagnosis, age at
diagnosis, seizure disorder, antipsychotic drugs, and serum carbamazepine
level did not explain this difference. The protection against hyponatremia
provided by the carbamazepine-lithium combination occurred despite
lithium's tendency to increase polyuria.
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