Does Mirtazapine Have a More Rapid Onset Than SSRIs?

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

Method: All double-blind studies comparingmirtazapine with SSRIs were analyzed. Included in the analysis todetermine speed of onset were 298 patients taking mirtazapine and285 taking an SSRI. Pattern analysis, which has been describedand used by other researchers, was employed to study speed ofonset.

Results: At the end of each of the 3 studies,the total number of responders for each of the drugs did notdiffer. However, the proportion of responders with onset ofpersistent 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 possibilitythat mirtazapine may have a more rapid onset than SSRIs. Thisobservation should be considered preliminary because of theretrospective nature of the analysis and the absence of a placebogroup.