Dose effects of tricyclic antidepressants in the treatment of acute depression - A systematic review and meta-analysis of randomized trials

Background: Tricyclic antidepressants (TCA) continue to be an important group of drugs, but it is unclear whether a dose-response relationship is supported by high-level evidence. Methods: Systematic review in the Cochrane Collaboration's Central Register of Controlled Trials (CENTRAL) of studies randomizing patients to at least two doses of one TCA, complemented by searches in Medline, Embase, and PsycInfo. In multilevel regression, we calculated the standardized mean difference (SMD) in antidepressant efficacy per mg TCA dose increase, and we analyzed drop-outs due to adverse events. Finally, we computed random effects meta-analyses of all dose comparisons investigated in a minimum of two studies. Results: Out of 5365 studies screened, we included 15 randomized trials on 24 comparisons of 14 different dose contrasts. We found a statistically non-significant positive effect of increasing the dose: 0.34 SMD with 100 mg/d dose increase ([-0.03; 0.70] p = 0.073). While several comparisons showed no clear signal of a dose gradient, 300 mg of imipramine/desipramine is statistically significantly superior to 150 mg (SMD: 0.80 [0.28; 1.33], p = 0.003, I-2: 0%). Drop-outs increased with higher doses, albeit not statistically significantly: Odds ratio (OR) of 1.44 with 100 mg dose increase [0.54; 3.86]. Overall, risk of bias was high. Limitations: Limited number of studies with mainly high risk of bias. Conclusions: So far, data on a dose-response relationship in TCAs from direct dose comparisons are inconclusive. Clinically, escalation to high doses may be justified if side effects are bearable.

Automated summary

The study found that increasing the dose of tricyclic antidepressants has a slightly positive effect on antidepressant efficacy, but it is not statistically significant overall. While some comparisons showed a dose gradient, it was not significant in general, and higher doses of imipramine/desipramine were significantly superior to lower doses in efficacy. Drop-out rates increased with higher doses, but not significantly.