Fast Fact and Concept #98: Intrathecal drug therapy for pain

Title: Fast Fact and Concept #98: Intrathecal drug therapy for pain

Author(s): Gary M. Reisfield, M.D. and George R. Wilson, M.D.

Intrathecal drug delivery can be an invaluable adjunct in the management of severe pain when meticulous application of conventional drug therapy proves ineffective or produces intolerable side effects. Intrathecal analgesia is distinguished from epidural analgesia by catheter location within the neuraxis. In the former, the catheter lies within the subarachnoid space, where small quantities of medication have direct access to spinal drug receptor sites. In the latter, larger doses of medication (necessitated by epidural fat and vascular uptake) must diffuse across the dura to reach these receptors. Potential advantages of intrathecal ? relative to epidural ? techniques are:

Ease of catheter placement, particularly in the presence spinal pathology.
Superior analgesia in the following settings:
- Presence of epidural pathology, e.g. metastatic disease, radiation fibrosis, vertebral compression.
- Widespread pain, multiple pain locations, and pain distant from catheter site, especially upper body.
- Pain poorly responsive to high-dose epidural therapy.
Fewer catheter problems, e.g. catheter migration, tip occlusion.
Lower dose requirements may reduce side effects and lower drug costs.

There exists a spectrum of intrathecal system options - from a simple, percutaneous catheter/external pump to a totally implanted system. Choice is based on life expectancy, performance status and available professional expertise. Pharmacoeconomic modeling suggests that the percutaneous catheter may be the most economic option for patients with prognoses of days to a few months.

Arner and Arner (1985) demonstrated a relative responsiveness of pain mechanisms to intraspinal opioids as follows: continuous somatic > continuous visceral > intermittent somatic > intermittent visceral > neuropathic > cutaneous (ulcers or fistulas). An opioid alone is likely to be effective for nociceptive pain syndromes. Addition of coanalgesics, including local anesthetics and/or clonidine is usually necessary for neuropathic pain syndromes.

Complications may occur from a) the procedure (e.g. post-spinal headache), b) medications (e.g. opioid-related respiratory depression, sedation, urinary retention, pruritis), and c) hardware (e.g. catheter kinking/disconnection/dislodgement, infection). Major contraindications to intrathecal catheter placement include coagulopathy, infection at catheter insertion site, and sepsis.

References
Bennett G, Burchiel K, Buchser E, Classen A, Deer T, et al: Clinical guidelines for intraspinal infusion: report of an expert panel. J Pain Symp Manage. 2000;20 (2;suppl):S37-S43.
Ferrante FM: Neuraxial infusion in the management of cancer pain. Oncology. 1999; 13 (5;suppl 2):30-36.
Mercadante S: Problems of long-term spinal opioid treatment in advanced cancer patients. Pain. 1999;79:1-13.
Arner S, Arner B: Differential effects of epidural morphine in the treatment of cancer related pain. Acta Anesthesiol Scand. 1985;29:32-36.

Copyright/Referencing Information: Users are free to download and distribute Fast Facts for educational purposes only. Citation for referencing. Reisfield GM and Wilson GR. Fast Facts and Concepts #98 Intrathecal drug therapy for pain. September 2003. End-of-Life Physician Education Resource Center www.eperc.mcw.edu.

Disclaimer: Fast Facts provide educational information, this information is not medical advice. Health care providers should exercise their own independent clinical judgment. Some Fast Fact information cites the use of a product in dosage, for an indication, or in a manner other than that recommended in the product labeling. Accordingly, the official prescribing information should be consulted before any such product is used.

Creation Date: 9/2003

Format: Handouts

Purpose: Instructional Aid, Self-Study Guide, Teaching

Audience(s)

Training: Fellows, 3rd/4th Year Medical Students, PGY1 (Interns), PGY2-6, Physicians in Practice

Specialty: Anesthesiology, Emergency Medicine, Family Medicine, General Internal Medicine, Geriatrics, Hematology/Oncology, Neurology, OB/GYN, Ophthalmology, Pulmonary/Critical Care, Pediatrics, Psychiatry, Surgery

Non-Physician: Nurses

ACGME Competencies: Medical Knowledge, Patient Care

Keyword(s): Addiction, Chronic non-malignant pain, Controlled substance regulations, Pain, Pain assessment, Pain treatment

The Fast Facts series is distributed for educational use only and does not constitute medical advice. For the most current version of Fast Facts visit the EPERC web site at www.eperc.mcw.edu. This mirror version is provided subject to copyright restrictions for educational use within the Inter-Instutional Collaborating Network on End-of-Life Care (IICN).