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Absorption and bioavailability of nebulized morphine
J Chrubasik1, H Wüst, G Friedrich
1Department of Anesthesiology, University Hospital, Düsseldorf, FRG.
Abstract:
During anaesthesia seven patients received a bolus of morphine 10 mg injected into the nebulization reservoir placed between the tracheal tube and the anaesthetic circle (IH). Five days after operation the same seven patients received morphine 10 mg i.m. On both occasions, venous blood samples were taken before and every 15 min after administration over 4.5 h for measurement of free morphine immunoreactivity by radioimmunoassay. There was marked individual variation in the serum morphine concentrations produced following each route of administration. The maximum serum morphine concentration following inhaled morphine was approx. six times lower than that after morphine i.m. and the time of occurrence differed significantly (P less than 0.001). The individual relative bioavailabilities of inhaled morphine varied from 9% to 35%, with a mean of 17%.
Insights
Inhaled morphine delivered via nebulization resulted in significantly lower serum concentrations compared to intramuscular injection. This study quantifies the bioavailability of inhaled morphine, finding it to be approximately 17% on average.
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.