The Effect of Dexamethasone on Cerebrospinal Fluid Monoamine Metabolites and Cortisol in Psychiatric Patients

The effect of 1 mg dexamethasone on CSF levels of 5-hydroxyindoleacetic acid (5 HIAA), homovanillic acid (HVA) and cortisol (CS) was investigated in 100 psychiatric inpatients: 45 subjects had their lumbar punctures 1-4 days following dexamethasone administration, and the results were compared with those from 55 other patients investigated before drug ingestion. All patients were women, and none had received psychotropic medication for at least two weeks before the study. Seven subjects consented to two LPs both before and after dexamethasone. As expected, cortisol in the CSF significantly decreased after dexamethasone: the decrease was greatest 10 hours following the drug. HVA showed a weak and transient elevation after 10 hours only. CSF 5 HIAA was found to be significantly increased in postdexamethasone samples and high levels were still found even after 82 hours. Diagnostic differences (major or minor depression, schizophrenia, alcohol abuse or dependence) did not account for the observed differences. Repeated CSF examinations in seven subjects corroborated these findings: all cortisol values were decreased and all 5 HIAA values were increased after dexamethasone while HVA values showed random changes. The data may suggest that serotonergic mechanisms may be involved in dexamethasone action in the CNS. In addition, dexamethasone administration can alter CSF 5 HIAA level, a possible factor which should be taken into consideration in CSF studies.