Platelet serotonin (5-HT) levels in interferon-treated patients with hepatitis C and its possible association with interferon-induced depression.

Interferon-associated depression is a frequent side effect of antiviral therapy for chronic hepatitis C. The aim of the present study was to investigate the correlation between platelet serotonin (5-hydroxytryptamine, 5-HT) concentrations and IFN-induced depression.The study represents a secondary analysis of a previously published trial on the efficacy of SSRI medication in HCV patients on IFN therapy. Ninety-three patients were longitudinally assessed for depression and platelet serotonin. Evaluation time points were: prior to IFN therapy, at weeks 4, 12, and 24 of IFN treatment, and 4 weeks after antiviral treatment. Depression was assessed using the Hospital Anxiety and Depression Scale (HADS). Platelet serotonin concentrations were measured by ELISA.Platelet serotonin concentrations were significantly decreased during interferon therapy (p=0.001) in 74 of the 93 patients (79.6%). Clinically relevant depression occurred in 33.3% of patients - however, IFN-induced depression was not significantly linked to either baseline 5-HT concentrations or kinetics. In the subgroup of patients with IFN-induced depression who received the selective serotonin reuptake inhibitor (SSRI) citalopram (20 mg daily, n=17), serotonin levels declined further during anti-depressant medication, becoming statistically significant within the first 2 weeks (p<0.001) of SSRI treatment.We demonstrate a significant impact of IFN and SSRI intake on platelet serotonin levels, suggesting a biochemical analogy between 5-HT metabolism in blood platelets and the CNS. Platelet 5-HT levels might serve as a surrogate marker for patient adherence to antiviral and anti-depressant medication. For the prediction of IFN-induced depression, however, platelet 5-HT measurements are not suitable.