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Plasma codeine and morphine concentrations after a single oral dose of codeine phosphate
Journal of Clinical Pharmacology
|August 1, 1990
Summary
This study measured codeine and morphine plasma levels after a 60 mg codeine phosphate dose in healthy volunteers. Results show minimal morphine formation, with free morphine comprising only 2.7% of free codeine.
Area of Science:
- Pharmacokinetics
- Analytical Chemistry
Background:
- Codeine is an opioid analgesic.
- It is metabolized to morphine, its active metabolite.
Purpose of the Study:
- To quantify plasma concentrations of codeine and its metabolite morphine.
- To determine the extent of morphine formation from codeine in healthy volunteers.
Main Methods:
- High-performance liquid chromatography (HPLC) was used for sensitive and specific analysis.
- Plasma samples were collected from ten healthy volunteers at 0.5, 1, 3, and 6 hours after a single 60 mg oral dose of codeine phosphate.
Main Results:
- Mean peak codeine plasma concentration was 88.1 ng/mL, reached at 1.2 hours.
- Mean peak morphine concentration was 2.7 +/- 0.6 ng/mL.
- The mean ratio of the area under the plasma concentration-time curve for morphine to codeine was 0.027, indicating morphine constituted approximately 2.7% of codeine.
Conclusions:
- Oral codeine phosphate administration results in limited conversion to morphine in healthy individuals.
- The contribution of morphine to the overall effect of codeine is likely minimal based on these plasma concentration data.