Intrathecal Therapy

Intrathecal or Intraspinal Drug Delivery (IDD)

Overview

In intrathecal drug delivery, pain medications and/or medications used for spasticity are introduced directly to the spinal fluid (intrathecal space) through a drug delivery system comprised of a pump and catheter. The intrathecal space is usually accessed from the lumbar region of the lower back. With this method, less medication is necessary than if medication were taken orally, and fewer side effects are seen. Newer intrathecal drugs such as ziconotide can be effective at reducing pain, and can only be given intrathecally.

Indications

There are many indications for the use of IDD in the case of both malignant and non-malignant pain and spasticity. However, in general, IDD should be considered when other conservative therapies have failed and non-intrathecal therapy regimens (i.e. oral, intravenous, or transdermal) are not adequately controlling symptoms and/or non-intrathecal regimens are causing significant side effects. (1)

Medications

Currently, the only medications that are approved by the U.S. Food and Drug Administration (FDA) for intrathecal administration are morphine, ziconotide and baclofen. However, recent literature supports the use of many other opioid and non-opioid medications for patients who cannot tolerate the on-label FDA medications. The other medications must be obtained through special compounding pharmacies to ensure sterility and proper concentration. This is especially important when multiple medications are used in the IDD. Of note, there is ongoing research into novel non-opioid medications, such as resiniferatoxin, which has the potential to be helpful in cancer pain. (2)

Procedure Overview

For this therapy, the doctor places a catheter beneath the skin and into the space along the spine (the intrathecal space) to release the medicine into the cerebrospinal fluid that bathes that area. In this way, the drug quickly reaches the part of the body that relays nerve signals and the drug exerts its effects directly. During an initial trial, while the patient stays at the hospital, medication is delivered through the catheter for a variable time period depending on how long it takes to achieve an optimal dosage level. If the effect is satisfactory, the next step is to implant the infusion pump. The pump is implanted under the skin, usually in the abdomen, in a “pocket” between skin and muscle tissue. There are two types of pumps: fixed rate and variable rate pumps. Fixed rate pumps do not require a battery. Instead fixed rate pumps operate mechanically and are powered by a gas pressure chamber surrounding a flexible inner reservoir. Variable rate pumps have a battery and integrated microelectronic circuits that control drug delivery. This allows the drug delivery rate to be changed if necessary. However, because of the battery, the variable rate pumps may need to be replaced over time. Implantation takes place under general anesthesia with local anesthetic for optimal pain control.

Pump Refill Procedure

Per FDA regulations, pumps should be filled every 6 months, but the interval varies between weekly in non-cancer pain up to every 6 months in stable, chronic pain patients. There are many different ways to refill a pump. Using sterile precautions, a pump can be refilled by accessing the fill port with a needle and the template that is provided with the refill kit. The port may also be located using imaging such as fluoroscopy – a type of X-ray – or ultrasound. The clinician must first empty any remaining volume from the pump and verify that that volume equals the amount that was expected, based on information from the device programmer.

Complications

For the most part with IDD therapy, complications and serious adverse events are rare. In general, IDD therapy complications relate to surgical issues, medication issues, or device issues. Shortly after the pump is implanted, serious surgical complications might include bleeding, infection, neurological injuries or post-dural puncture headache (from a persistent spinal fluid leak). Opioid administration might cause life-threatening respiratory depression. Other medication-related issues may include hormonal fluctuations, peripheral edema (swelling) and persistent nausea. A granuloma (a small collection of immune cells) may form at the catheter tip, especially when specific types of medication are used at high concentrations. A pump malfunction, meanwhile, might lead to a potentially life-threatening withdrawal from baclofen.

Efficacy

There is excellent evidence for the use of intrathecal baclofen for spasticity. Meanwhile, recent studies have shown IDD combined with typical medical management for cancer pain helps reduce pain and side effects and improves 6-month survival rates. There are many other studies that show the efficacy of IDD for cancer pain. The use of IDD for chronic non-cancer pain can also be very helpful for certain individuals, although more research is needed. (2)

Cost Effectiveness

In general, IDD has been found to be very cost effective. In chronic non-cancer pain patients, when compared with conventional medical management, IDD is more effective after around two years. However, in cancer pain patients, due to the dynamic nature of their pain, IDD can be cost effective in as little as three months. (3)

One of the most effective ways to treat chronic pain, when all other attempted
treatments including surgery has failed, is to put medications directly into the spinal fluid. Intrathecal therapy precisely directs medications to the nerves carrying the pain signals
into the spinal cord.

This method uses medications that will reduce the transmission of the pain signals that reach the brain (where you are actually feeling the pain).

The beauty of this technique is that it is tested with a temporary trial of intrathecal medications, delivered in a minimally invasive way. If significant pain relief is achieved, the system can be implanted as an outpatient.

Treatment

This treatment method has many advantages that make it unique.

1.    The medications are not being delivered by the
bloodstream throughout the body.

2.    Some of the medications used are only available for
intrathecal use and cannot be delivered by any
other route of administration.

3.    It is possible that no opioid (narcotic) medication
needs to be used for successful pain relief.

Often combinations of medications with different mechanisms of action are used to successfully treat intractable chronic pain. None of the medications are systemic (throughout the body) since they are placed directly into the spinal fluid that bathes the spinal cord and the nerves transmitting the pain signals toward the brain. (Use of some of these medications intrathecally represents an off-label use, but has been used this way for years as best-practice).

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