Morphine concentrations in plasma after intramuscular administration.

Area of Science:

• Pharmacology
• Clinical Medicine
• Analytical Chemistry

Background:

• Preoperative medication is crucial for patient management.
• Understanding drug pharmacokinetics, like morphine, is vital for optimizing therapeutic outcomes.
• Radioimmunoassay provides a sensitive method for quantifying drug levels in biological samples.

Purpose of the Study:

• To quantify plasma morphine concentrations after intramuscular administration.
• To investigate the pharmacokinetic variability of morphine in patients.
• To explore the relationship between plasma morphine levels and pain relief.

Main Methods:

• Intramuscular administration of morphine at 0.2 mg/kg body weight.
• Plasma morphine concentrations measured using radioimmunoassay.
• Data collected over 24 hours post-injection.

Main Results:

• Peak plasma morphine concentrations occurred approximately one hour post-injection.
• Significant inter-individual variation (sevenfold) in plasma morphine concentrations was observed.
• Measurable morphine or its metabolites were detected in plasma for up to 24 hours.
• No correlation was found between plasma morphine concentration and pain relief in patients undergoing therapeutic abortion.

Conclusions:

• Intramuscular morphine exhibits significant pharmacokinetic variability.
• Current dosing may not consistently correlate with patient-reported pain relief.
• Further research is needed to personalize morphine administration for effective pain management.