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Plasma and CSF morphine concentrations after i.m. and epidural administration
Abstract:
Morphine concentrations in plasma and CSF after i.m. and epidural morphine administration were assayed in patients undergoing surgery of the low abdomen. Morphine concentration in CSF after i.m. administration of this drug is remarkably lower than morphine concentration in plasma. The highest value is attained in CSF after about 90' and is followed by a slow downsloping to lowest values, which were observed 4 hours after drug administration. Kinetics of morphine passage into plasma after epidural administration is similar to that found after i.m. administration. In the latter experimental condition (epidural administration), concentrations of morphine in CSF 30' after administration are markedly lower than those found in plasma. However, 60 min. after epidural administration plasma and CSF morphine concentrations are similar, in particular CSF concentrations are 4 to 8 times higher than those obtained after i.m. administration. Such high levels persist for a long time.
Insights
Intramuscular and epidural morphine show different concentrations in cerebrospinal fluid (CSF) and plasma. Epidural administration results in significantly higher and longer-lasting morphine levels in the CSF compared to intramuscular routes.
Area of Science:
- Pharmacology
- Neuroscience
- Clinical Medicine
Background:
- Understanding drug distribution is crucial for effective pain management.
- Morphine is a widely used analgesic, but its pharmacokinetics vary by administration route.
- Cerebrospinal fluid (CSF) and plasma concentrations reflect drug delivery to the central nervous system and systemic circulation.
Purpose of the Study:
- To compare morphine concentrations in plasma and CSF following intramuscular (i.m.) and epidural administration.
- To elucidate the pharmacokinetic profiles of morphine via different routes in patients undergoing lower abdominal surgery.
Main Methods:
- Assay of morphine concentrations in plasma and CSF.
- Administration of morphine via intramuscular and epidural routes in surgical patients.
- Kinetic analysis of drug distribution over time.
Main Results:
- Intramuscular morphine yielded markedly lower CSF concentrations than plasma concentrations.
- Following epidural administration, CSF morphine levels were initially lower than plasma but became similar at 60 minutes.
- Epidural morphine achieved CSF concentrations 4 to 8 times higher than i.m. administration, with prolonged elevated levels.
Conclusions:
- Epidural morphine provides superior and sustained central nervous system exposure compared to intramuscular administration.
- The route of morphine administration significantly impacts its distribution kinetics and concentration in CSF.
- These findings have implications for optimizing analgesic strategies in postoperative pain management.