Fast Fact and Concept #028: Subcutaneous Infusions

2nd Edition

Author(s): David E. Weissman, MD

A parenteral opioid infusion is the standard of care for managing moderate-severe pain or dyspnea when the oral/rectal route is unavailable and/or frequent dose adjustments are needed. As death nears, the burden of maintaining IV access, especially in the home setting can be enormous. An alternative delivery route is the subcutaneous (SQ) route for continuous infusions, Patient Controlled Analgesia (PCA), or intermittent bolus opioid injections.

Drugs

Morphine, hydromorphone (Dilaudid), fentanyl, and sufentanil can all be safely administered as SQ bolus doses or continuous SQ infusion. Methadone infusions cause frequent skin irritation; one case series reported successful use of methadone with concurrent dexamethasone infusion and frequent site rotation.

Dosing equivalents

Dose conversion ratios between the intravenous and SQ route for all the above listed opioids are not well established. For morphine, the ratio appears to be close to 1 mg IV = 1mg SQ.

Pharmacokinetics

SQ infusions can produce the same blood levels as chronic IV infusions. There is no data to suggest that cachectic, febrile or hypotensive patients have problems with drug absorption.

Volume and Drug Choice

The limiting feature of a SQ infusion is the infusion rate; in general, SQ tissue can absorb up to 3 cc/hr. At low opioid requirements morphine is generally the drug of choice based on availability and cost; a switch to hydromorphone is indicated for a high opioid requirement due its’ higher intrinsic potency (6:1), thus the need for a smaller infusion volume.

Administration

Use a 25 or 27 gauge butterfly needle—place on the upper arm, shoulder, abdomen or thigh. Avoid the chest wall to prevent iatrogenic pneumothorax during needle insertion. The needle can be left indefinitely without site change unless a local reaction develops—typically, patients can keep the same needle in place for up to one week at a time.

Toxicity

Local skin irritation, itching, site bleeding or infection can occur; of these, skin irritation is the most common, managed by a needle site change.

Patient acceptance

Patients readily appreciate the ease of SQ administration as an alternative to IV access.

References

Bruera E, Brenneis C, Michaud M, et al. Use of the subcutaneous route for the administration of narcotics in patients with cancer pain. Cancer 1988;62:407-411.

Storey P. Subcutaneous infusion for control of cancer symptoms. J Pain Symptom Manage 1990;5:33-41.

Waldman CS, Eason JR, Rambohul E, et a;. Serum morphine levels—a comparison between continuous SQ and IV infusion in post-operative analgesia. Anaesthesia 1984;39:768-771.

Mathew P and Storey P. Subcutaneous methadone in terminally ill patients: manageable local toxicity. J Pain Symptom Manage 1999;18:49-52.

Fast Facts were edited by David Weissman MD, Palliative Care Center, Medical College of Wisconsin until January 2007.  For comments/questions write to the current editor, Drew Rosielle MD: drosiell@mcw.edu. The complete set of Fast Facts is available at EPERC: www.eperc.mcw.edu

Copyright/Referencing Information : Users are free to download and distribute Fast Facts for educational purposes only. Citation for referencing: Weissman DE . Subcutaneous Opioid Infusions Fast Fact and Concept #28; 2nd Edition, July 2005. End-of-Life Palliative 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: 11/2000; 2nd Edition, July 2005

Purpose: Instructional Aid, Self-Study Guide

Audience(s)

ACGME Competencies: Medical Knowledge, Patient Care

Keyword(s): Pain>opioids