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What is baclofen?
Spasticity is a motor disorder characterized by tight or stiff
muscles that may interfere with voluntary muscle movements. Baclofen is a muscle
relaxant medication. It is commonly used in adults to decrease spasticity
related to spinal cord injuries or multiple sclerosis. Baclofen is also used to
treat children who have cerebral palsy.
How does baclofen work?
Spasticity is caused by an imbalance of excitatory and inhibitory input in
the spinal cord. This imbalance causes hyperactive muscle stretch reflexes.
These reflexes result in involuntary spasms and increased muscle tone.
Baclofen works by blocking the release of excitatory neurotransmitters in the
spinal cord. Ideally, baclofen restores the balance of excitatory and inhibitory
input to reduce muscle hyperactivity. In this way, it also allows more normal
motor movements.
Why is intrathecal baclofen preferred over oral baclofen?
Baclofen can be taken orally (by mouth in pill form) or delivered
intrathecally (as an injection in the spine). Oral baclofen causes side effects
that may limit its usefulness, especially when prescribed for children. Of the
oral baclofen delivered throughout the body, only a small portion goes to the
spinal fluid where it is needed to work.
With an intrathecal delivery system, baclofen is delivered right to the
target site in the spinal cord. Because the intrathecal system continuously
delivers baclofen in small doses directly into the spinal fluid, there are fewer
and less severe side effects than that seen with the oral medication.
What is the baclofen pump system?
The baclofen pump system is the intrathecal (directly into the spinal fluid)
method of delivering the medication. The system consists of a catheter (a small,
flexible tube) and a pump. The pump--a round metal disc, about one inch thick
and three inches in diameter--is surgically placed under the skin at the level
of the abdomen.
The pump stores and releases prescribed amounts of medication through the
catheter. The pump has a 10-mL fluid capacity and can be refilled by inserting a
needle through the skin into a filling port (called the diaphragm) in the center
of the pump.
Who is a candidate for the pump system?
Anyone who has spasticity and weighs over 30 pounds can be considered for the
baclofen pump system. The pump system is appropriate when adjustable and
potentially reversible treatment is desired, but cannot be achieved with oral
medication.
How will my doctor know if the baclofen pump system will work?
If your doctor recommends the baclofen pump system, you will have a trial of
the intraspinal therapy to test the potential effectiveness of the medication.
During the medication trial, a small needle is placed near the spinal cord in
the lower back. The medication is injected into the spinal canal and you are
assessed over 8 to 10 hours to determine how well the medication treats the
spasticity. If your muscles don't relax during the first trial, a larger dose
may be given the next day to determine its effectiveness.
This procedure causes minor discomfort. You may experience temporary muscle
weakness due to the relaxing effect of the medication. This is caused by
receiving a large dose of medication all at once during the trial.
Patients who experience positive results with the intrathecal medication can
decide with their doctor if they should have a baclofen pump system implanted.
How is the pump system implanted?
The pump is surgically placed just underneath the skin, usually in the lower
abdominal area. The procedure to place the pump lasts from 1 Ѕ to 2 hours.
The procedure may be performed under local anesthesia (pain-relieving
medication that numbs the area while you remain awake) or general anesthesia
(medication given by an anesthesiologist that induces sleep). Children are most
often given general anesthesia and are asleep for the entire procedure.
The catheter is inserted through a needle and guided into the spinal canal,
close to where pain pathways enter the spinal cord.
The other end of the catheter is tunneled under the skin to the abdomen,
where a pocket is created. There, the pump is implanted through an incision in
the abdomen, anchored to surrounding tissue, and connected to the catheter. Once
the incision is closed, the pump reservoir is filled with the dosage of baclofen
prescribed by the physician.
How is the medication dispensed?
With a programmable pump, a tiny motor moves the medication from the pump
reservoir through the catheter. Baclofen flows freely through the spinal fluid,
affecting the nerves to control muscle hyperactivity.
Adjustments in the dose, rate, and timing of the medication can be made by
your doctor, using an external programmer. The pump system can be set to
dispense medication continuously or at certain times of the day. The pump can
also be easily reprogrammed if necessary.
Patients must return to their doctor's office for pump refills and medication
adjustments, typically every 2 to 3 months. The pump system is taken out and
replaced at the end of the battery's life span (which is usually 3 to 5 years).
What are the side effects of baclofen?
Some side effects of baclofen include dizziness, drowsiness, headache, nausea
and weakness. Problems with the infusion pump can cause either overdose or
sudden withdrawal of baclofen.
What are the potential advantages of the baclofen pump system?
Typically, the intrathecal baclofen pump:
- Effectively reduces spasticity and involuntary spasms,
promoting a more active lifestyle, better sleep, and reduced need for oral
medications.
- Continuously delivers baclofen in small doses directly to the
intraspinal fluid, increasing the therapeutic benefits and causing fewer and
less severe side effects than that seen with the oral medication.
- Can be individually adjusted to allow infusion rates that vary
over a 24-hour period. It can be turned on or off or programmed to infuse
different levels of medication throughout the day, depending on your needs.
For example, people who find their spasticity helpful in maintaining leg
extension for standing or walking can have a lower infusion rate during the
day.
- Can be turned off if spasticity reduction has shown no benefit.
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