Drug Delivery Devices

Intrathecal (spinal fluid space) drug delivery uses an implantable drug infusion system (pump) to deliver very low amounts of opioids or other analgesics directly into the intrathecal space. Continuous infusion provides a stable concentration of drug in the spinal fluid, thus avoiding fluctuations associated with bolus injections.

Although morphine is currently the only FDA approved opioid agent, other medications are being currently used for patients who cannot tolerate morphine or are not responsive to it.

These pumps are used for patients who failed simpler and less invasive modalities.

Patients need a clear understanding of all the risks, benefits and alternatives of this modality.

A thorough understanding of the potential long-term side effects of the medications is required. This treatment modality is designed to ease the pain and improve function but is not in and of itself a cure for the underlying problem.

Chronic conditions responsive to an implantable pump are: intractable leg and back pain after back surgery, old compression fractures, spinal stenosis, cancer pain and certain chronic neuropathic (nerve) painful syndromes.

There are 5 phases of treatment: initial patient education, patient selection, screening test, preoperative care and maintenance.

A screening test is performed prior to the actual implantation of the pump. This is performed over a few days, when the actual medication is given to the patient in the intrathecal or the epidural space. The medication is given in incremental doses, until a response is noted or side effects are present. During the screening test the patient keeps a pain diary in which pain severity is recorded on a scale from 0 to 10. Only those patients who pass the screening test are considered to be candidates for the actual implant. A 50 % improvement of the pain is usually required before proceeding with the implantation. A thorough psychological examination is also required.

The actual implantation takes place in the operating room, most of the time under general anesthesia. The patient uses a girdle in the immediate postoperative period. Usually the patient is kept overnight in the hospital for observation.

Maintenance requires regular refills of the pump at two to three months intervals. This is done in the office, as an outpatient procedure.