Female Wistar rats were treated with various doses of progesterone orally via the diet or via the SC route. Oral treatment resulted in enhanced progesterone levels in the liver as measured by radioimmunoassay. There were up to 3-fold increases in activity of ethylmorphine demethylation by isolated microsomes; metabolism of aminopyrine and benzphetamine was less enhanced, that of aniline and p-nitroanisol showed no distinct increases. Progesterone also caused increases in liver size and total liver protein by up to 50%; total liver DNA showed only slight, insignificant increments. These studies suggest that hepatic effects of progesterone are similar to those previously described with synthetic steroids such as pregnenolone-16 alpha-carbonitrile (PCN) and cyproterone acetate.
The kinetics of a single 1200 mg oral dose of oxaprozin, a nonsteroidal antiinflammatory agent of the propionic acid class, was studied in 22 healthy female volunteers aged 21 to 64 years. Eleven subjects had been taking a conjugated estrogen preparation for at least 3 months; the other 11 subjects served as control women who were not taking conjugated estrogens. Mean pharmacokinetic variables in control and conjugated estrogen groups were: volume of distribution, 15.1 vs 14.1 l; elimination half-life, 59.8 vs 54.2 h; clearance, 3.2 vs 3.1 ml/min; peak plasma concentration, 84.8 vs 90.7 micrograms/ml, respectively. None of the differences were significant. However, the time of peak concentration (8.9 vs 4.0 h) was significantly longer in the control group than in the conjugated estrogen group, respectively (p less than 0.05). Oxaprozin clearance, accomplished by a combination of oxidation and conjugation, is unimpaired by coadministration of conjugated estrogens.
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