Duloxetine is a potent norepinephrine and serotonin inhibitor of CNS. It was found to be efficacious in management of chronic low back pain (CLBP) but the predictors that generate response are not examined in detail. In this double blind trial, the predictors of response to Duloxetine for CLBP has been evaluated and it has been determined that early improvement and pain sites affects the overall response rate of Duloxetine in CLBP.

Duloxetine showed confirmed effectiveness in chronic low back pain (CLBP) management. This study investigated the predictors of response to Duloxetine for CLBP.

Patients received 60 mg/day Duloxetine for 12-14 weeks.  The proportion of subjects with ≥30% decrease in Brief Pain Inventory (BPI) average pain at 12-14 weeks was considered as the primary endpoint. The comparison of patients with ≥30% and ≥50% pain decrease in duloxetine and placebo groups were considered as the secondary outcome.  The number of painful body sites, early improvement, duration of CLBP, sex, age, and baseline BPI average pain score were the variables for responder analyses that measured according to the Michigan Body Map.

Duloxetine-treated patients obtained ≥30%  and ≥50% pain decrease as compared to the placebo.  An early improvement was correlated with the elevated likelihood of ≥30% pain reduction in the Duloxetine-treated patients. Men were slightly less likely than women to obtain ≥30% or ≥50%  pain reduction. The average pain score subgroups: CLBP duration, age, and baseline BPI showed similar response rates. As compared to patients with isolated CLBP, patients with ≥two painful sites were more likely to respond to Duloxetine 60 mg relative to placebo.

Early pain decline was characteristic of overall response. Duloxetine is known to provide more benefit among patients with multiple painful sites.