Dose increase of S-Adenosyl-Methionine and escitalopram in a randomized clinical trial for major depressive disorder.

Background: The optimal dose of S-adenosyl methionine (SAMe) for major depressive disorder (MDD) remains unclear. The objective of this analysis was to address whether a dose increase provided further improvement in cases of insufficient response using data from an existing randomized clinical trial.

Methods: Sixty-five patients with MDD who failed to respond to SAMe 1,600 mg/day, escitalopram 10 mg/day, or placebo for 6 weeks were treated with doubled doses of the allocated treatments for the following 6 weeks. Changes in 17-item Hamilton Depression Rating Scale, Inventory of Depressive Symptomatology-Self Rated, and Systematic Assessment for Treatment Emergent Events-Specific Inquiry were compared between the lower and higher dose treatments in each treatment group and among the higher dose treatments of SAMe, escitalopram, and placebo.

Results: Various depression severity scores decreased significantly for all three treatment arms during the higher dose treatment. No within-group and between-group differences were found in any of the efficacy measures when comparing the doses and treatments. There was a significant difference in reported abdominal discomfort among patients receiving the higher dose of SAMe (31.3%), compared to escitalopram (8.7%) and placebo (3.8%) (χ2=7.32, p = 0.026).

Limitations: The sample size was relatively small. The study duration for dose increase was relatively short.

Conclusions: Patients with MDD failing to respond to 1,600 mg/day of SAMe may improve after increasing the dose to 3,200 mg/day, but we cannot rule out the contribution of a placebo effect and time-related improvement. The risk of abdominal discomfort may be increased with higher doses of SAMe.