Does Mirtazapine Have a More Rapid Onset Than SSRIs?

Background: A single study utilizing a cross-sectional analysis of scores on the Hamilton Rating Scale for Depression (HAM-D) suggested that mirtazapine has a more rapid onset than selective serotonin reuptake inhibitors (SSRIs). Analysis based on the HAM-D may favor drugs with sleep-producing effects. The purpose of the present study was to determine if a review of all studies comparing an SSRI with mirtazapine, utilizing persistent improvement as the dependent variable, would suggest that mirtazapine had a more rapid onset than SSRIs.

Method: All double-blind studies comparing mirtazapine with SSRIs were analyzed. Included in the analysis to determine speed of onset were 298 patients taking mirtazapine and 285 taking an SSRI. Pattern analysis, which has been described and used by other researchers, was employed to study speed of onset.

Results: At the end of each of the 3 studies, the total number of responders for each of the drugs did not differ. However, the proportion of responders with onset of persistent improvement in week 1 was greater for mirtazapine (13%, 38/298) than for the SSRIs (6%, 18/285; chi2 = 6.95, df = 1, p = .008).

Conclusion: These data support the possibility that mirtazapine may have a more rapid onset than SSRIs. This observation should be considered preliminary because of the retrospective nature of the analysis and the absence of a placebo group.

J Clin Psychiatry 2001;62(5):358-361