Aliment Pharmacol Ther 2011; 34: 1306-1317 SUMMARY: Background Treatment of hepatitis C with peginterferon and ribavirin is associated with psychiatric side-effects, frequently necessitating dose reduction or therapy cessation. Aim To assess the efficacy of prophylactic escitalopram to prevent psychiatric side-effects during peginterferon and ribavirin treatment in a randomised, double-blind, placebo-controlled trial. Methods Seventy-nine hepatitis C patients were treated with peginterferon and ribavirin. Patients received escitalopram (n = 40, 10 mg) or placebo (n = 39), which was initiated together with peginterferon and ribavirin. Primary outcomes were an increase of two points or more on the items reported sadness, inner tension and impaired concentration of the Montgomery-Asberg Depression Rating Scale, and hostile feelings of the Brief Anxiety Scale. Secondary outcome was the development of depression diagnosed by the Mini-International Neuropsychiatric Interview. Measurements were performed at baseline, week 4, 12 and 24 during anti-viral treatment, and 24 weeks thereafter. Results The incidence of psychiatric side-effects was significantly lower in patients treated with escitalopram compared with placebo for all primary and secondary outcomes, except for impaired concentration: reported sadness 27.5 vs. 48.7% (P = 0.052), inner tension 17.5 vs. 38.5% (P = 0.038), impaired concentration 55.0 vs. 66.7% (P = 0.288) and hostile feelings 22.5 vs. 43.6% (P = 0.046) (escitalopram vs. placebo, Chi-squared test). The sum scores of all four endpoints showed an overall beneficial effect of escitalopram (P = 0.009, Mann-Whitney U-test). Depression occurred in 12.5% of the patients in the escitalopram-group vs. 35.9% in the placebo-group (P = 0.015, Chi-squared test). Conclusions Prophylactic treatment with escitalopram is effective in the prevention of psychiatric side-effects during interferon-based treatment of hepatitis C.