Last Resort for Pain Control: Intrathecal Drug Delivery

Patients with severe, constant pain that has not responded to any other treatment may be candidates for something called intrathecal (IT) drug delivery. Intrathecal means within the spinal canal. The spinal canal is the opening for the spinal cord to travel from the brain down to the bottom of the spine. Delivering pain medication through the spinal canal directly into the spinal fluid is a fast and effective way to override pain messages to the brain.

This type of pain control is done with a pump that can be implanted (placed) inside the body. The pump is usually placed in the abdomen with a catheter (tube) up into the spinal canal. When placed internally, the intrathecal pump provides a constant stream of pain relieving medications into the spinal fluid. Various medications can be used. They all have advantages and disadvantages. Opioids (narcotics) are commonly tried first.

It’s really a last resort effort to gain control of pain when everything else has been tried and failed. And even these implantable pumps aren’t used without a trial first. Electrodes are placed on the outside of the spine first to see if the patient can get good pain relief this way. The external (outside) unit is left on for one to two weeks before considering implantation.

Some pumps seem to work better than others for individual patients. There can be a trial and error period when different drugs (or combination of drugs) are used to get the desired results (pain relief) with the fewest side effects. Common side effects with any of the opioid medications include nausea, dizziness, confusion, difficulty walking, and problems with memory.

The intrathecal (IT) drug delivery system has been in use for 30 years now, so there have been some studies to help guide doctors when prescribing the system and choosing the specific drugs. There are two groups of chronic pain patients who can benefit from this treatment approach: those with cancer pain and those with noncancer pain.

Pain Medicine News has published updates on the use of IT drug therapy for both groups. In this issue, Dr. Richard L. Rauck, Director of Clinical Research on Pain at Wake Forest University School of Medicine (North Carolina) presents an update on the use of IT for noncancer pain.

Patients considering IT therapy should be told that complete pain relief is rare. They can expect some improvement (up to 50 per cent reduction in pain) — enough that they can function better. They may be able to tolerate their pain enough to complete daily activities and participate in life more comfortably. Dr. Rauck provides physicians prescribing the medications used in IT therapy with details about each drug.

Physicians who specialize in pain management will benefit from the discussion about specific drugs, types of drug trials to use, determining dosages, and calculating ratios when combining drugs. Drugs may be given in steady streams of smaller dosages or with a single larger dosage called a bolus. The prescribing doctor makes the determination based on patient problem, drug (or drugs) used, and type of system used.

Companies making the implantable units are continuing to improve these delivery systems. The systems now come with options to choose from and can be programmed to provide medications on a schedule or at the patient’s request (self-administered). The devices are more durable than when they first came out. And the batteries last longer. Manufacturers of a new programmable IT drug pump called Prometra hope to have it on the market in the New Year (2010).

Patients must be educated about this method of pain control. Besides the side effects mentioned, there can be problems with low blood pressure that can suddenly switch to dangerous high blood pressure. It’s possible to develop a tolerance to the drug. This means the patient no longer gets the same pain relief with the standard prescribed dosage and must start taking more of the medication — and that can lead to even more problems.

Too strong of a reaction to a medication may require a switch to another drug. Even the process of withdrawing from one drug to try another can cause problems. Then the catheter used to deliver the drug can get blocked or kinked. And patients run out of their drugs. That’s just the short list of things that can go wrong with IT drug therapy.

Sometimes the body forms fibrous tissue around the device that can be a problem. This is an immune inflammatory reaction. The immune cells that travel to the area attempt to wall off the device forming a ball of cells called a granuloma. Development of a granuloma requires immediate attention to avoid serious neurologic problems. The drug must be stopped. A series of MRIs will then be done over time to make sure the granuloma is going away.

Patients must let their doctor know any time the pain increases and they lose the pain relief initially offered by IT drug therapy. This may be a sign of a granuloma forming or an indication that a change in drug selection is required.

IT therapy isn’t for everyone. Like many other modalities used to manage pain, it is a tool that works well for some, but not all, patients. With continued improvements in the technology available for the implantable pumps, more patients might benefit from this treatment approach in the years ahead. Keeping abreast of the new developments will remain an important part of the pain specialist’s job. Updates like this one from Dr. Rauck are very helpful.