Start of a selective serotonin reuptake inhibitor (SSRI) and increase of antiparkinsonian drug treatment in patients on levodopa: SSRI and Parkinson's disease

Aims We determined whether the start of selective serotonin reuptake inhibitors (SSRI) in levodopa users was followed by a faster increase of antiparkinsonian drug treatment. Methods Selected were all levodopa users of 55 years and older from the PHARMO prescription database. The rate of increase of antiparkinsonian drug treatment was compared using Cox's proportional hazard model for starters of SSRI (n = 15) with starters of tricyclic antidepressants (TCA) (n = 31) and with patients not using antidepressants (n = 304), and was adjusted for age, gender, and duration of levodopa use. Results The hazard ratio for the SSRI group compared with the TCA group was 4.2 (95% confidence interval 1.4, 12.6) and compared with the second control group was 2.7 (1.2, 5.2). Conclusions The start of SSRI therapy in levodopa users is followed by a faster increase of antiparkinsonian drug treatment.