Citalopram: differential sleep/wake and EEG power spectrum effects after single dose and chronic administration. 
The sleep/wake effects of the selective serotonin re-uptake inhibitor citalopram were studied in both a single-dose study with three dose levels (0.5, 2.0 and 5.0 mg/kg), and a 5-week chronic administration study (15 mg/kg/24 h).  Single doses of citalopram resulted in a dose-dependent inhibition of rapid eye movement (REM) sleep.  After chronic citalopram treatment there was a sustained REM sleep inhibition.  Single doses of citalopram resulted in only minor changes in non-REM (NREM) sleep as well as in NREM EEG power spectral density.  Chronic administration resulted in a major shift from SWS-2 to SWS-1.  The observed corresponding changes in EEG power density were regional.  A 30 to 40 percent reduction of power density in the 0.5-15 Hz range in the fronto-parietal EEG derivation was seen for the whole 8-h registration period.  In the fronto-frontal EEG derivation only minor changes were seen.  A decreasing trend in NREM sleep power density between 0.5 and 7 Hz, usually seen during the course of the light period, was not observed in the chronic condition, but was seen in control and single-dose condition, suggesting altered diurnal distribution of slow wave activity in the chronic condition.  The data indicate that acute and chronic administration of citalopram shows clear differences in sleep effect, which may be caused by alteration of serotonergic transmission, and may be related to the antidepressant effect.