Chapter 66: Choosing Intrathecal Medication

INTRODUCTION

• Intraspinal delivery of drugs via implantable drug delivery systems (IDDS) has been available since the early 1980s.

• These devices allow for precise delivery of drugs for treatment of pain and spasticity.

• The delivery is medications in the intraspinal or intrathecal space allows delivery of medications directly to their site of receptor binding in the spinal column at much smaller doses than systemic administration.

• The result is potent analgesic effect with lower systemic side effects.

IDDS comprises of a pump implanted in a subcutaneous pocket usually in the abdomen and attached to a catheter that is tunneled under the skin and inserted in the intrathecal space of the spinal cord at the appropriate level (Figure 66-1). The pump available is programmable or nonprogrammable. The nonprogrammable pump runs at a constant flow rate with dose adjustments made by changes in the concentration of medications. The programmable pump is programmed to deliver the drug or admixture at a controlled rate based on the drug concentration and dose requirements of the patient.

Complications related to the pump and catheter system:

• Complications should be addressed prior to choosing and adjusting intrathecal drug medications.¹

• The most common operational problems are related to either pump programming or motor stalling.

• Pump programming errors are most likely to occur when drug concentrations are changed.

• Verification of drug concentration, daily dose, volume, and refill date is absolutely necessary.

• A motor stall is typically caused by gear shift wear. The incidence is low (0.5%-2.2%) and can be detected with radiographic examination.²

• New SynchroMed pumps are equipped with electronic logs to detect and report motor stall issues.

• Catheter malfunctions include kinks, holes, or blockages that prevent accurate delivery of medications.¹

• Other complications include catheter fibrosis or inflammation and granuloma formation.

Granuloma:

• Development of noninfectious inflammatory mass or granuloma has been reported 0.1% to 5% of patients with implantable pumps.^3,4

• Physicians should be suspicious of possible granuloma if patient complains of increased pain that was previously controlled and/or neurological deficits of weakness and sensory loss.

• Granulomas have been reported most frequently with morphine followed by hydromorphone and fentanyl.

Once patient has selected for intrathecal drug therapy, drug selection is the next step. The polyanalgesic consensus conference (PACC) panel has developed recommendations on the rational use of intrathecal analgesics. This PACC panel has reviewed preclinical and clinical research and experience in 2000, 2003, 2007, and 2011.⁵ The current standard of care of intrathecal therapies reflects on current knowledge from literature and clinical experience. Analysis of published literature is combined with clinical experience of a large panel of scientist and clinicians to form recommendations regarding the use of intrathecal analgesics to treat chronic pain. It is this ...