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First-pass effect of morphine in rats.
Abstract
In order to evaluate the first-pass effect of morphine, the pharmacokinetic parameters of 3H-morphine (5 mg/kg) were studied in male Sprague-Dawley rats by comparing the plasma concentrations after oral, intravenous and intraportal administration. Morphine was almost completely absorbed from the gastrointestinal tract, since no significant difference was found in the cumulative urinary excretion of radioactivity after intravenous and oral administration. Route of administration had no affect on plasma half-life (about 115 minutes) of unchanged morphine. In contrast, the area under the plasma concentration vs. time curve for morphine after oral administration was only about 18%, and after intraportal administration about 40% of that observed after intravenous administration. It can be estimated that approximately two-thirds of the overall first-pass effect (82%) of morphine is due to extraction and/or metabolism in the intestine and the remaining one-third by the liver.
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Cited by
Morphine-3-glucuronide - a potent antagonist of morphine analgesia
Smith, M. T., Watt, J. A., & Cramond, T. (1990) · Life Sciences · doi:10.1016/0024-3205(90)90619-3 · Cited by 337
Walczak, J.-S., Pichette, V., Leblond, F., Desbiens, K., & Beaulieu, P. (2005) · Neuroscience · doi:10.1016/j.neuroscience.2005.02.010 · Cited by 133
Komura, H., & Iwaki, M. (2011) · Drug Metabolism Reviews · doi:10.3109/03602532.2011.597401 · Cited by 78
Metadata
- Authors
- Iwamoto, K., & Klaassen, C. D.
- Venue
- The Journal of Pharmacology and Experimental Therapeutics
- Publisher
- Elsevier BV
- Published
- 1977-01
- Volume
- 200
- Issue
- 1
- Pages
- 236-244
- ISSN
- 0022-3565 (ISSN-L)
- OpenAlex
- W4407043713
- Cited by
- 160
- References
- 0
- FWCI
- 3.21
- Type
- journal article
- Language
- en
- Open access
- closed
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- CoChat. (2026). Citation check: First-pass effect of morphine in rats. https://app.cochat.ai/papers/10.1016/s0022-3565(25)30761-5
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- Iwamoto, K., & Klaassen, C. D. (1977). First-pass effect of morphine in rats. The Journal of Pharmacology and Experimental Therapeutics. https://doi.org/10.1016/s0022-3565(25)30761-5
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Contains information from the Semantic Scholar Academic Graph Datasets, made available under the ODC Attribution License (ODC-BY 1.0).
Semantic Scholar’s data is described in: Kinney, R., et al. (2023). The Semantic Scholar Open Data Platform. arXiv:2301.10140.
