Diffusion of morphine-6-beta-D-glucuronide into the neonatal guinea pig brain during drug-induced respiratory depression
Morphine-6-beta-D-glucuronide (M6G) is an active metabolite of morphine. In a previous study, M6G depressed respiration in the neonatal guinea pig, becoming more potent with aging, a finding that is confirmed in the current study. After s.c. injection, M6G is absorbed into plasma, crosses the blood-...
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Published in | The Journal of pharmacology and experimental therapeutics Vol. 271; no. 1; pp. 118 - 124 |
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Main Authors | , |
Format | Journal Article |
Language | English |
Published |
United States
American Society for Pharmacology and Experimental Therapeutics
01.10.1994
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Subjects | |
Online Access | Get full text |
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Summary: | Morphine-6-beta-D-glucuronide (M6G) is an active metabolite of morphine. In a previous study, M6G depressed respiration in
the neonatal guinea pig, becoming more potent with aging, a finding that is confirmed in the current study. After s.c. injection,
M6G is absorbed into plasma, crosses the blood-brain barrier and is present in the central nervous system at the time of maximal
M6G-induced ventilatory depression. No hydrolysis of M6G to morphine is detected in either plasma or brain tissue by high-performance
liquid chromatography. About 30% more M6G is in plasma in 3-day-old than in 7-day-old pups after drug administration (P <
.05). Mean brain concentrations of M6G are 12% higher on day 3 than day 7, but the difference is not statistically significant.
Brain-to-plasma ratios of M6G do not differ after 5 or 15 mg/kg of M6G or with age (mean ratio = 0.037). Brain drug concentration
is a linear function of plasma drug levels (r2 = 0.84), suggesting M6G crosses the blood brain barrier by diffusion. Differential
systemic absorption or central nervous system distribution of M6G cannot explain enhanced respiratory depression with aging.
Morphine-3-beta-D-glucuronide (M3G) also crossed the blood-brain barrier, but is less permeable than M6G (mean brain-to-plasma
ratio = 0.022). Contrary to reports in the literature, M3G at a dose of 75 mg/kg, does not stimulate respiration in this study.
Morphine administration to neonatal guinea pigs produces measurable plasma and brain levels of M6G and M3G. |
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Bibliography: | ObjectType-Article-2 SourceType-Scholarly Journals-1 ObjectType-Feature-1 content type line 23 ObjectType-Article-1 ObjectType-Feature-2 |
ISSN: | 0022-3565 1521-0103 |