Factors affecting discontinuation of initial treatment with paroxetine in panic disorder and major depressive disorder.

Objective: The aims of the present study were to analyze the association between discontinuation of paroxetine (PAX) and the genetic variants of the polymorphism in the serotonin transporter gene-linked polymorphic region (5-HTTLPR) in Japanese patients with panic disorder (PD) and major depressive disorder (MDD).

Methods: The 5-HTTLPR genotype was determined by polymerase chain reaction method. PAX plasma concentration was measured by high-performance liquid chromatography to confirm adherence.

Results: When comparing between the PD and MDD patients with the chi-square test and Fisher's exact test, the PD patients had a significant and higher discontinuation rate due to non-adherence than did the MDD patients (13.5% [7/52] versus 0% [0/88], respectively; P<0.001). MDD patients had a significant and higher discontinuation rate due to untraceability than PD patients (12.5% [11/88] versus 1.9% [1/52]; P=0.032). Multilogistic regression revealed a tendency for the long/short and short/short genotypes to affect discontinuation due to adverse effects in PD patients (25.0% versus 6.3%, respectively; P=0.054).

Conclusion: The results indicate that the 5-HTTLPR genotype might contribute to the discontinuation of initial PAX treatment due to adverse effects in PD patients.