The effect of digoxin on the response to lithium therapy in mania.

Patients suffering from manic-depressive psychosis, manic type (ICD 296.0), were treated with lithium carbonate and randomly allocated to two groups, one received digoxin and the other matching placebo for 7 days. Severity of mania was rated by psychiatrists on the Manic Rating Scale and Analogue Line on days 0 and 7 and by nurses daily on the Hargreaves Rating Scale, Psychotic Rating. Fourteen patients received digoxin and lithium carbonate and 14 patients received placebo and lithium carbonate. Improvement in the placebo lithium group was significantly greater than that in the digoxin lithium group. This trial suggests, therefore, that the effect of inhibition of membrane cation carrier is to reduce the response to lithium. This result is in keeping with our hypothesis that an increase in Na-K ATPase is essential to the therapeutic effect of lithium carbonate. It does not, however, exclude the possibility that the observations resulted from the inhibition by digoxin of lithium entry into the brain.