Absorption and bioavailability of nebulized morphine

Area of Science:

• Pharmacology
• Anesthesiology
• Drug Delivery

Background:

• Morphine is a potent opioid analgesic commonly used for pain management.
• Investigating alternative routes of morphine administration, such as inhalation, is crucial for optimizing patient care and potentially reducing systemic side effects.
• Understanding the pharmacokinetic profile of inhaled morphine is essential for its clinical application.

Purpose of the Study:

• To compare the serum concentrations and bioavailability of morphine administered via inhalation (IH) versus intramuscular (IM) injection.
• To assess the pharmacokinetic variability of inhaled morphine in patients undergoing anesthesia.

Main Methods:

• Seven patients received morphine 10 mg via nebulization during anesthesia and 10 mg intramuscularly five days post-operation.
• Venous blood samples were collected pre-administration and every 15 minutes for 4.5 hours post-administration.
• Serum free morphine concentrations were measured using radioimmunoassay to determine immunoreactivity.

Main Results:

• Marked individual variations in serum morphine concentrations were observed for both administration routes.
• Maximum serum morphine concentrations were approximately six times lower following inhaled morphine compared to IM administration.
• The time to reach maximum concentration differed significantly between the two routes (P < 0.001).
• Individual relative bioavailability of inhaled morphine ranged from 9% to 35%, with a mean of 17%.

Conclusions:

• Inhaled morphine delivered through a nebulizer results in substantially lower peak serum concentrations and bioavailability compared to intramuscular morphine.
• Significant inter-individual variability exists in the pharmacokinetic response to inhaled morphine.
• Further research is warranted to explore the therapeutic potential and optimal dosing of inhaled morphine in clinical settings.