The use of alcohol with Chlorpromazine should be avoided due to possible additive effects and hypotension. Chlorpromazine may counteract the antihypertensive effect of guanethidine and related compounds. Chlorpromazine prolongs and intensifies the action of CNS depressants, eg anesthetics, barbiturates and narcotics. When Chlorpromazine is administered concomitantly, about 1/4 to 1 /2, the usual dosage of such agents is required. When Chlorpromazine is not being administered for potentiation, it is best to stop such depressants before starting Chlorpromazine treatment. These agents may subsequently be reinstated at low doses and increased as needed.
Note: Chlorpromazine does not intensify the anticonvulsant action of barbiturates. Therefore, dosage of anticonvulsants, including barbiturates should not be reduced if Chlorpromazine is started. Instead, start Chlorpromazine at low doses and increase as needed.