Opiate effects on 5-fluorouracil disposition in mice

Area of Science:

• Pharmacology
• Drug Metabolism
• Toxicology

Background:

• Morphine is an opioid analgesic.
• 5-fluorouracil (5-FU) is a chemotherapy drug.
• Interactions between analgesics and chemotherapy drugs can affect treatment efficacy and toxicity.

Purpose of the Study:

• To investigate the impact of morphine on the pharmacokinetic disposition of 5-fluorouracil (5-FU) in mice.
• To determine if morphine alters 5-FU plasma levels, clearance, or excretion.

Main Methods:

• Mice received subcutaneous morphine or saline, followed by intravenous 5-FU administration (bolus or infusion).
• Plasma and urine samples were collected to measure 5-FU concentrations using High-Performance Liquid Chromatography (HPLC).
• Pharmacokinetic parameters, including plasma clearance and elimination half-life, were analyzed.

Main Results:

• Morphine significantly increased plasma concentrations of 5-FU.
• Prior morphine administration reduced 5-FU plasma clearance rate and increased its elimination half-life.
• Morphine's effects on 5-FU disposition were dose-dependent and reversible with naltrexone, indicating opioid receptor involvement.
• Renal excretion of 5-FU was not affected by morphine.

Conclusions:

• Concomitant use of morphine significantly reduces the plasma clearance rate of 5-FU in mice.
• The observed effect is primarily due to reduced hepatic elimination of 5-FU, not altered renal excretion.
• These findings suggest potential drug interactions that could influence 5-FU chemotherapy efficacy and toxicity.