Platelet paroxetine binding and fluoxetine pharmacotherapy in posttraumatic stress disorder: preliminary observations on a possible predictor of clinical treatment response.

Recent open clinical trials have found the selective serotonin reuptake inhibitor (SSRI) fluoxetine to be beneficial in the treatment of posttraumatic stress disorder (PTSD) symptoms. We have reported previously that the binding of a newer SSRI, paroxetine, to blood platelets is decreased in PTSD patients compared to normal control subjects. In the current study, pretreatment platelet paroxetine binding data were analyzed for ten Vietnam combat veterans who were treated clinically with fluoxetine for PTSD, diagnosed on the basis of the Structured Clinical Interview for DSM-III-R. Specific binding of 3H-paroxetine is reported in terms of the dissociation constant (Kd) and the maximum density of binding sites (Bmax). Based on our previous findings we hypothesized that decreased platelet 3H-paroxetine binding would be associated with positive therapeutic response to subsequent treatment with fluoxetine. Global clinical improvement ratings, conducted blind to the biochemical data, were used to separate patients into five maximal responders and five partial responders. The results indicated that maximal responders had lower pretreatment Kd values (p = .016) and a trend toward lower pretreatment Bmax values (p = .075) than the partial responders. These preliminary findings may warrant further study of platelet SSRI binding as a possible predictor of SSRI treatment response in PTSD patients.