Abstract
Baclofen has become one of the most widely used antispastic medications. Although effective at therapeutic doses, baclofen toxicity is a continuum of tolerable side effects, overdose, tolerance, and withdrawal. A GABAB agonist, baclofen inhibits synaptic reflexes at the spinal cord level. Baclofen improves spasticity associated with spinal cord lesions, multiple sclerosis and other neurologic disorders, and has been used off-label for intractable hiccups, bladder spasticity, trigeminal neuralgia, and gastroesophageal reflux disease. The drug is absorbed completely from the gastrointestinal tract with peak serum concentrations reached in approximately two hours. Baclofen is eliminated predominantly (85%) by the kidneys. Renal insufficiency delays clearance of baclofen, and limited case reports have detailed increased complications in patients with renal insufficiency. Complications can also occur from dosing errors or device-related problems (e.g., leakage, catheter fracture, disconnection, occlusion, infection). Baclofen's dose-related adverse effects reflect its CNS inhibitory properties: Somnolence, CNS depression, respiratory depression, hypotension, cardiac conduction abnormalities, seizures, and thermoregulation disturbances. Some studies have reported cases of rhabdomyolysis, coma, and death. There are few multi-center reviews of baclofen toxicity, and case reports of baclofen overdose may have been affected by patient's age, comorbidities, concomitant use of another CNS depressant, and renal impairment. Oral baclofen overdose complications have occurred with doses greater than 60mg/day, with most doses greater than 200mg requiring critical care management. Baclofen withdrawal symptoms have also been reported, including: Hallucinations, seizures, hyperthermia, rhabdomyolysis, and status epilepticus. These complications are often transient or reversible. Although there is no baclofen antagonist, patients who have overdosed on baclofen often respond quickly to symptomatic care that may include: Atropine for bradycardia, vasodilators for hypertension, and phenytoin or diazepam for seizure control. Acute overdose, however, often requires additional critical care management with airway management that may include endotracheal intubation and mechanical ventilation, electrolyte repletion, and deep vein thrombosis (DVT) precautions, neurologic monitoring, thermoregulation, and restraints. Patients with renal insufficiency may require hemodialysis, which is an effective mechanism to reduce toxic drug levels. For those with intrathecal baclofen overdose, CSF drainage and subsequent cautious baclofen replacement may be necessary to treat withdrawal. As serum levels are not always available, baclofen toxicity is primarily a clinical diagnosis. Further studies are needed to develop improved detection and quantitation of baclofen, especially in the critical care setting. © 2015 by Nova Science Publishers, Inc. All rights reserved.