Complications associated with the use of intrathecal baclofen can be categorized into those associated with the pump and those due to the drug.
The most problematic complications have been due to the pump and its catheter. Most of the more serious ones occurred early and simply reflected problems in developing new technology. There have been reports of incorrect delivery of baclofen at rates exceeding those programmed. These occurred with early models of the pump. The pump and its catheter can fail or break, necessitating a surgical intervention to rectify the situation. The pump or the tissues surrounding it may become infected, requiring its removal and treatment with intravenous antibiotics. The system has safeguards to minimize the potential for the infection to spread via the catheter into the CSF space.
Two types of complications are seen with baclofen: those experienced when the drug is given within its therapeutic range (so-called adverse reactions) and those seen with overdoses of the drug. The adverse reactions are deemed minor and include light headedness, drowsiness, double vision, dry mouth and nausea/vomiting. Seizures (in those with a history of epilepsy), diarrhea and urinary retention (inability to completely empty the bladder) or incontinence (inability to hold urine) have also been reported. If the drug is given in an inappropriately high amount or is allowed to run up the spinal canal in concentration (both of which are more of a risk during the trial injection during candidacy evaluation), an ascending muscle weakness and loss of tone will occur, followed by sleepiness and depression in respiration. This can then progress to coma and breathing cessation. This evolves over hours, affording those looking over the individual ample time to intercede. The response to this is to provide respiratory support including artificial ventilation if needed, stop delivery of the drug if it is occurring, give the drug physostigmine, and wait for the baclofen to wear off (up to two days). There have been no reports of adverse, long-term effects in those who have experienced this complication provided respiration was supported during the episode.