Effect of concentration and mode of intrathecal baclofen administration on soleus H-reflex in patients with muscle hypertonia

Objectives

Assess spinal reflex excitability after increasing intrathecal baclofen (ITB) flow by manipulation of drug concentration and mode of administration.

Methods

The effect of concentration was assessed by comparing changes in H-reflex (H/M ratio) 1–6 h after a 50 μg ITB bolus at 50 μg/ml concentration administered manually via lumbar puncture (LP, duration 1–2 min, n = 27) to a 50 μg bolus at 500 μg/ml concentration programmed through the pump and delivered via intrathecal catheter (IC, duration 10 min) above simple continuous dose (25–100 μg/day, n = 16). The effect of mode of administration was assessed by comparing peak changes in H/M ratio after 50 μg IC bolus above simple continuous dose (complex continuous mode, n = 27) to simple continuous mode only (n = 22) at equivalent daily doses (75–150 μg/day).

Results

H/M decrease was faster and overall greater after LP than IC bolus (mean 1-h 77% vs. 63%, p = 0.012; 1–6 h 91% vs. 82%, p < 0.001, respectively). H/M ratio also decreased significantly more with complex (91%) than simple continuous mode of administration (78%, p = 0.025).

Conclusions

Lower ITB concentration and complex continuous mode of administration lead to greater decrease in H/M ratio.

Significance

Decreased spinal reflex excitability after adjustment of drug and pump parameters to increase ITB flow may result in better clinical response.