Comparative bioavailability of a morphine suppository given rectally and in a colostomy

Area of Science:

• Pharmacology
• Gastroenterology
• Clinical Pharmacy

Background:

• Morphine is a potent opioid analgesic.
• Colostomy patients may require alternative routes for medication administration.
• Rectal suppositories are a common dosage form.

Purpose of the Study:

• To evaluate the bioavailability of morphine suppositories administered via colostomy.
• To compare colostomy administration to standard rectal administration.
• To assess the variability and predictability of morphine absorption through a colostomy.

Main Methods:

• Eight patients with a colostomy participated in the study.
• Morphine chloride (20 mg) was administered as a suppository, first rectally, then via colostomy after a washout period.
• Plasma morphine levels were measured for 8 hours post-administration.
• Bioavailability was calculated relative to rectal administration.

Main Results:

• Significant variability in morphine bioavailability was observed with colostomy administration (mean 43% of rectal bioavailability; range 0.1-127%).
• Four patients had consistently lower plasma morphine concentrations after colostomy administration.
• Three patients showed minimal detectable morphine levels via colostomy.
• One patient exhibited higher plasma concentrations after colostomy administration.

Conclusions:

• Administration of morphine suppositories via a colostomy results in highly variable and unpredictable bioavailability.
• The absorption of morphine through a colostomy is unreliable compared to rectal administration.
• Morphine suppository administration via colostomy is not recommended for clinical use.