The onset of action of antidepressant drugs was investigated on the basis of two independent multicenter, double-blind efficacy studies comparing amitriptyline (n = 120), oxaprotiline (n = 120), imipramine (n = 506) and moclobemide (n = 580) with placebo (n = 189 + 191). The samples consisted of in- and outpatients diagnosed, according to Diagnostic and Statistical Manual (DSM)-III criteria, as suffering from major depressive disorder. Measures of efficacy criteria were the Hamilton Rating Scale for Depression (HAM-D), the Hamilton Rating Scale for Anxiety (HAM-A) and the Zung Self-Rating Depression scale. By using the Sustained Relative Improvement (SRI) criterion, onset of action was determined in each individual patient as that time point in the 30 day observation period at which a 20% baseline score reduction was achieved without subsequent deterioration. Analogously, a response to treatment was defined as a 50% baseline score reduction. As expected, highly significant differences between active drugs and placebo were found with respect to the total number of improvers and responders. Significant differences between treatment modalities surfaced in the percentage rate as well as the time distribution of premature withdrawals. Yet, unexpectedly, among improvers, the time spans to onset of improvement were found to be independent of treatment modality as indicated by virtually identical cumulative percentages of improvers throughout the whole observation period. The picture was essentially the same for the HAM-A and Zung assessments, except for a significant time lag between observer- and self-ratings. In particular, our analyses revealed no evidence for a delayed onset of action under various antidepressants with large biochemical and pharmacological differences in comparison to placebo. Moreover, the early onset of improvement was highly predictive of later outcome: on average, 70% of the patients showing improvement within the first 14 days became responders. Applying survival-analytical methods, we found that differences between active treatments and placebo emerged within the first 5 days and reached a point of maximum distinction around day 14. After this time point, differences between treatment modalities remained constant until the end of the observation period. According to our data, 20–25% of the patients were, on average, ‘true’ drug responders, thus suggesting that the therapeutic qualities of antidepressants do not lie in the suppression of symptoms, but rather are related to their ability to elicit and maintain certain conditions which allow recovery in a subgroup of patients who would otherwise remain non-responders.

We examined the relation between dosage and efficacy, and the predictors of response to milnacipran. There was no difference between 50 and 100 mg dose. However, the 100 mg dose had a faster onset of action than the 50 mg dose. An age and an episode have been predictors of milnacipran.

The issue of early onset of action (EOA) of an antidepressant was addressed by several authors. Unfortunately so far there is neither consensus nor convention on the definitions of EOA, or on measures and methods of assessments. There are several quite different approaches to the statistical analysis of the data. Our objective was to compare the results concerning EOA obtained by different statistical techniques applied on a data set which was generated by several independent conclusive double-blind, placebo controlled randomised trials with two antidepressants. The following statistical techniques were used: 1) statistically significant difference for the first time; 2) statistically significant and clinically relevant difference for the first time; 3) pattern analysis; 4) classical survival analysis without ‘sustained response’; 5) survival analysis with sustained response. The advantages and drawbacks of different methods are discussed.

The benefits of an antidepressant with an early or rapid onset of action include a more rapid resolution of the debilitating symptoms of depression, a potential reduction in the risk of suicide and cost savings associated with a reduction in hospitalization. While these benefits are valuable, this promise has yet to be fulfilled by any antidepressant. Venlafaxine is a unique serotonin-noradrenaline reuptake inhibitor (SNRI) which produces rapid and prolonged desensitization of β-adrenergic receptors in preclinical studies after both acute and chronic administration of venlafaxine. Results from placebo-controlled and active comparator clinical studies provide evidence that venlafaxine may have an early onset of activity which is most apparent at higher dosages. The early onset is most apparent with rapid escalation of the venlafaxine dosage, and the incidence, therefore, of side effects tends to be higher early after initiating therapy with venlafaxine. Thus, venlafaxine may fill the long awaited need for an antidepressant with an early onset of action.

Background: Rapid response to antidepressant therapy is desirable and may be particularly critical in elderly patients with major depressive disorder (MDD).

Methods: Findings are based on post-hoc analyses from a double-blind trial of elderly patients with MDD ≥ 65 years, randomly assigned 2:1 to duloxetine 60 mg QD (N = 207) or placebo (N = 104) for 8 weeks. Depression and pain measures included the Geriatric Depression Scale (GDS), 17-item Hamilton Depression Scale (HAMD17), CGI-Severity, and Visual Analog Scale (VAS) for overall pain. The time to response and remission for duloxetine compared with placebo was evaluated using Cox proportional hazards (PH) modeling, Kaplan-Meier estimation, and categorical repeated measures analysis.

Results: Significant improvements of estimated HAMD17 response and remission rates for duloxetine started at week 2 (P = 0.022 and P = 0.033, respectively). Time to HAMD17 response and remission were significantly shorter for duloxetine versus placebo (P < 0.001 and P = 0.004, respectively). Placebo-referenced duloxetine hazard ratios (HR) for HAMD17 response and remission were 2.03 (P = 0.002) and 2.01 (P = 0.006), respectively. Results for GDS-based response (HR = 1.54, P = 0.023) and remission (HR = 1.54, P = 0.104) rates were consistent with the HAMD17 findings. Patients ≥75 years (n = 93) responded with similar rapidity to duloxetine compared with those <75 years (n = 199, P > 0.10 for all PH treatment-by-age interactions). The placebo-referenced duloxetine HR for time to 50% reduction in overall pain was 1.75 (P = 0.024) for patients with moderate to severe pain.

Conclusion: Duloxetine demonstrated a faster time to antidepressant response and improvement in self-reported pain as compared with placebo.

Clinical trial registry number for this study: NCT00062673, at www.clinicaltrials.gov.