How long to give an SSRI to work ?

An important review article and meta-analysis, Early Treatment Responses of Selective Serotonin Reuptake Inhibitors (SSRIs) and clomipramine in pediatric OCD was published in the Journal of the American Academy of Child and Adolescent Psychiatry (October, 2016, p 851-859).


The most important finding was that “more than 85% of the improvement observed on SSRI compared to placebo in pediatric OCD trials was observed by week 2”. The current guidelines state that an 8 to 12 week trial of SSRIs is necessary, for both children and adults, although adults have a similarly rapid response.


Also, in answer to patients’ common question, “which SSRI is the best?”, there was no “significant differences among individual SSRI agents” (fluoxetine, fluvoxamine, sertraline, paroxetine).


There was no effect of maximum SSRI dosing (previously, it has been posited that OCD response required higher dosages, than, say, depression, and previous adult meta-analyses showed greater therapeutic response with higher SSRI dosages).


Clomipramine, a tricyclic antidepressant, also showed a rapid response (75% of benefit by week 2), and was more effective than SSRIs, compared to placebo (there were no direct drug-drug comparisons). However, clomipramine is not viewed as the first choice, due to its higher side effect burden of “weight gain, anticholinergic side effects, and arrhythmias”.


The major clinical implication of this article is that if there is no or minimal response after 2 weeks of SSRI treatment  in pediatric OCD, one should start seriously thinking about changing medications. It also suggests that the follow-up visit should be 2 weeks after starting the new medication, and not 4.


Apparently this is the case not only in OCD, but in major depression, and in both children and adults.

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