Baclofen is a gamma-aminobutyric acid (GABA) agonist which is used to suppress spasticity and the cravings suffered by alcohol and cocaine abusers. The intrathecal delivery system is a subcutaneous abdominal pump which transfers baclofen through a catheter to the spinal canal. Intrathecal baclofen allows for lower doses, fewer side effects, and easier drug maintenance. The patient and caregiver must be vigilant in watching for pump problems, which can result in overdose or withdrawal.
Muscular disorders characterized by spasticity or involuntary muscle spasms can prevent coordinated movement and are often caused by excessive GABA release. Baclofen acts to normalize the balance of excitatory and inhibitory neurotransmitters by controlling the action of GABA and relaxing the hyperactive muscles. It is prescribed to control spasticity in disorders such as multiple sclerosis, Lou Gehrig’s disease, spastic diplegia, and spinal cord injuries, and also has been used to treat alcohol and cocaine addictions.
Baclofen can be administered orally, but intrathecal baclofen administration into the spinal fluid appears to be most effective method, requires lower doses of the drug, and produces fewer side effects. A small titanium pump about 1 inch (2.5 cm) thick by 3 inches (7.6 cm) in diameter is placed near the waist just under the skin. The pump has a reloadable reservoir to store the drug and can be programmed to release the drug at the appropriate dose. A catheter transports the baclofen from the pump directly into the spinal canal. The pump is checked, reprogrammed, and reloaded in a doctor’s office every one to six months, and a new pump is implanted approximately every five to seven years when the battery is depleted.
Intrathecal baclofen treatment is typically recommended when spasticity is interfering with a patient’s personal safety or normal activity. This drug delivery method is fairly maintenance free, so it is advantageous when the burden of spasticity and patient care becomes excessive for a caregiver. Intrathecal baclofen may also be tried if the dose for oral baclofen was high and the side effects surpassed the benefits of the drug.
The dangers of intrathecal baclofen occur when a catheter problem develops, human error results in an improper pump setting, or when the wrong baclofen concentration is loaded into the reservoir. Problems can also occur when the patient fails to react to a pump alarm, warning of a malfunction or that the pump is almost empty. These issues can cause improper dose delivery and result in either an overdose or withdrawal. Signs of baclofen overdose include the return of poor muscle control, sleepiness, seizures, an inability to breath, and coma. Withdrawal is characterized by increased spasticity, sweating, rashes, fever, elevated heart rate, and, if left untreated, organ failure and death.
Overdosing or withdrawal can be avoided by carefully selecting patients who are either capable of monitoring their own pumps or have a responsible caregiver. The pumps need to be refilled and checked one week before the medication runs out. In addition, the patient and caregiver need to learn to recognize the early signs of both baclofen withdrawal and overdose and seek medical help immediately.