The lack of efficacy of different infusion rates of intrathecal baclofen in complex regional pain syndrome: a randomized, double-blind, crossover study.

OBJECTIVE

Intrathecal baclofen (ITB) is effective in the treatment of dystonia related to complex regional pain syndrome (CRPS). In a previous study, we noted that the responsiveness to ITB declined in 30% of patients once drug delivery was switched from an external to an implanted device associated with a reduction of the infusion rate (IR).

DESIGN

In a double-blind study, we investigated the effect of varying the IR at a fixed daily dose on the efficacy and safety of ITB in patients with CRPS-related dystonia. Patients were randomized to either slower infusion rate delivery (SIRD) or four-times faster infusion rate delivery (FIRD) for 2 weeks and were crossed over after a 1-week washout period.

PATIENTS

Patients were eligible if they experienced no beneficial response to ITB on dystonia despite a minimum dose of 600 µg/day, or because side effects limited dose escalation.

OUTCOME MEASURES

Primary outcome measures were changes in global dystonia and pain severity.

RESULTS

There were no significant differences between the FIRD and the SIRD groups for the median change of numeric rating scale dystonia (-0.3 [interquartile range {IQR} -1.1-0.5]), pain (0.1 [IQR -0.8-1.3]), and secondary outcomes, except for the frequency of adverse events, which was significantly higher during FIRD (12 vs 2). FIRD was preferred only by patients who were included because side effects to ITB prevented dose escalation.

CONCLUSIONS

Increasing the IR at a fixed daily dose is not associated with improvement of dystonia or pain but warrants further investigation in patients in whom side effects prevent further dose escalation.