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The bioavailability of morphine applied topically to cutaneous ulcers
Maria D C Ribeiro1, Simon P Joel, Giovambattista Zeppetella
1St Joseph's Hospice, Barts and the London NHS Trust, and University of London, United Kingdom.
Journal of Pain and Symptom Management
|May 4, 2004
Summary
Topical morphine for skin ulcers showed minimal systemic absorption in most patients. However, significant absorption of morphine and its metabolite morphine-6-glucuronide occurred in one patient with a large ulcer.
Area of Science:
- Pharmacology
- Dermatology
- Pain Management
Background:
- Topical morphine has shown analgesic effects on painful skin ulcers.
- Opioid receptors are present on peripheral nerve terminals, suggesting local action.
Purpose of the Study:
- To investigate the systemic bioavailability of topically applied morphine to cutaneous ulcers.
- To determine morphine and its metabolite levels in plasma after topical application.
Main Methods:
- Six hospice inpatients with skin ulcers received topical and subcutaneous morphine sulfate (10 mg each).
- Plasma concentrations of morphine, morphine-6-glucuronide (M6G), and morphine-3-glucuronide (M3G) were measured using HPLC.
- Treatments were administered over 4 hours, randomized, and separated by at least 48 hours.
Main Results:
- Morphine and its metabolites were undetectable in plasma for five out of six patients after topical application.
- In one patient with the largest ulcer, morphine and M6G were detected in plasma.
- Calculated bioavailability was 20% for morphine and 21% for M6G in the patient with the largest ulcer.
Conclusions:
- Topical morphine applied to skin ulcers is generally not systemically absorbed.
- The analgesic effect of topical morphine is likely local rather than systemic.
- Systemic absorption of topical morphine may occur in patients with large cutaneous ulcers.