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Norethindrone disposition following x-ionizing radiation in rats
Research Communications in Chemical Pathology and Pharmacology
|December 1, 1985
Summary
Ionizing radiation exposure alters norethindrone pharmacokinetics in rats, increasing its distribution and half-life. Hepatic clearance remains unaffected, suggesting radiation impacts membrane permeability rather than liver metabolism.
Area of Science:
- Pharmacology
- Radiation Biology
- Toxicology
Background:
- Ionizing radiation exposure can significantly impact physiological processes.
- Understanding drug pharmacokinetics after radiation exposure is crucial for patient management.
Purpose of the Study:
- To investigate the effects of ionizing x-irradiation on the pharmacokinetics of norethindrone in rats.
- To determine if radiation dose and time post-exposure influence norethindrone's absorption, distribution, metabolism, and excretion.
Main Methods:
- Norethindrone was administered via IV bolus injection to rats at various times (immediately, 3 days, 7 days) after exposure to different doses of x-rays (100, 300, 600 rads) or sham irradiation.
- Key pharmacokinetic parameters including volume of distribution (Vdarea), half-life, Mean Residence Time (MRT), and total body clearance were analyzed.
Main Results:
- No immediate changes in norethindrone pharmacokinetics were observed post-irradiation.
- At 3 days post-irradiation, significant increases in Vdarea, half-life, and MRT were noted, particularly at the 600 rads dose.
- These trends persisted at 7 days post-irradiation, though less pronounced. Total body clearance remained unchanged across all groups.
Conclusions:
- Radiation exposure, particularly at higher doses and delayed time points, alters norethindrone distribution and elimination half-life.
- The findings suggest that radiation may increase cell membrane permeability, leading to wider drug distribution.
- Hepatic biotransformation and clearance of norethindrone are not significantly affected by irradiation, implying preservation of hepatic drug-metabolizing enzyme function for highly extracted drugs.