Chronological milestones to guide drug change. When should clinicians switch antidepressants?

We attempt to identify the time when patients whose conditions are unimproved while receiving antidepressants are unlikely to respond and should have their treatment changed.

A total of 593 patients were studied. The course of treatment for patients was examined to determine the weeks at which patients who received drug therapy had a better chance of being rated as responders at the study end (week 6) vs patients who received placebo.

At the end of week 3, 19 (32%) of the 59 patients who received drug therapy and 6 (10%) of the 57 patients who received placebo and who never minimally improved were rated as responders at week 6. For those who showed no improvement by week 4, the effects of drug therapy and the placebo were equal. Patients who received drug therapy and whose conditions were unimproved but who had been minimally improved at some point had a superior prognosis with drug therapy vs placebo until week 4. Of those unimproved at week 4 but minimally improved at some point previously, 20 (39%) of the 51 patients who received drug therapy vs 3 (8%) of the 36 patients who received placebo were rated as responders at week 6. Of the 75 patients who minimally improved while receiving drug therapy at the end of week 5, 33 (44%) had a chance of being rated a responder at the end of week 6 vs 9 (26%) of the 35 patients receiving placebo.

Patients tolerant of an adequate dose, whose conditions have never been at least minimally improved by the end of week 4, should have their treatment regimen altered. These patients represented a minority of drug-treated patients in the sample studied (ie, 39/392 [10%]). Patients whose conditions minimally improve at some prior week but not after week 5 should have their treatment changed. Patients whose conditions minimally improve in week 5 should continue treatment until week 6.