Treatment approaches to major depressive disorder relapse. Part 1: dose increase

OBJECTIVE: Although continuing antidepressant treatment after patients have responded to medication has been shown to greatly reduce the risk of relapse, this risk is not eliminated. A number of theories have been proposed to account for this apparent loss of efficacy. A common initial approach to managing relapse is to increase the dose of antidepressant. We prospectively evaluated the likelihood of response to increasing the fluoxetine doses in patients relapsing during a long-term efficacy study of two fluoxetine dosing regimens. METHOD: Patients meeting the DSM-IV criteria for major depressive disorder with modified HAMD17 scores > or =18 and CGI-severity scores > or =4 were treated for 13 weeks with open-label 20 mg/day fluoxetine in a multicenter US study. Responders (n = 501) were randomized to 20 mg fluoxetine daily, placebo, or 90 mg enteric-coated fluoxetine weekly for 25 weeks of double-blind continuation treatment. If the patients relapsed during the continuation phase, they were offered a 25-week optional rescue treatment phase during which the study medication dose was increased as follows: (1) patients on placebo had treatment with fluoxetine 20 mg/day reinitiated, (2) patients on fluoxetine 20 mg/day had their dose increased to 40 mg/day, and (3) patients on a 90-mg weekly dose had their dose increased to 90 mg twice a week. The results of the rescue phase for the latter two groups who relapsed while on continuation treatment with fluoxetine are reported. Response was defined as a 50% reduction in the modified HAMD17 score since time of relapse and a CGI-severity score < or =2. Additional efficacy analyses included HAMD and CGI-severity changes from baseline to endpoint. Safety measures included assessment of treatment-emergent adverse events, vital signs, and laboratory measures. RESULTS: Overall, patients relapsing during the continuation treatment responded to an increased dose (57% of the 40-mg-daily group and 72% of the enteric-coated 90-mg-twice-weekly group). Mean modified HAMD17 scores decreased from a mean of approximately 20 to below 8 and were maintained for up to 6 months in the responders. Thirty-five percent of patients either did not respond or initially responded but again relapsed after augmentation of medication. CONCLUSIONS: The patients relapsing after initially responding to fluoxetine can benefit from an increase in fluoxetine dose. These results also generally support increasing dose as a first-line treatment strategy for a patient who has relapsed while taking a previously effective dose of an antidepressant. Increasing enteric-coated fluoxetine 90 mg once weekly to twice weekly appeared to be as well-tolerated and effective in restoring response as increasing a daily fluoxetine dose from 20 to 40 mg.