Evidence of tolerance to baclofen in treatment of severe spasticity with intrathecal baclofen.

In a retrospective study, changes in baclofen dose and complication frequency were recorded in 79 patients with intrathecal baclofen administration and the effect on nightly muscle spasms was measured over a mean observation period of 34 months, during which time an increase in the daily dose of baclofen during the first 1--1-1/2 years is notified. On subsequent pump fillings the daily dose of baclofen remained stable in the group of non-multiple sclerosis patients. In contrast, the group of multiple sclerosis patients showed a steady increase in their daily dose of baclofen. We found a frequency of complications of 0.014 monthly often due to catheter problems. There was a significant decrease in numbers of nightly muscle spasms in an 8 h recording period from 77+/-20 preoperatively and 9+/-3 (P=0.02) 3 months after surgery. The steady increase in the daily dose of baclofen in order to obtain adequate reduction in spasticity and nightly muscle spasms in the first 1--1-1/2 years cannot fully be explained by caution and difficulties in achieving the correct dose, but also indicates that tolerance to baclofen occurs. Complications are often due to infection or catheter problems.