[Removal of prednisone and prednisolone during plasma exchange]. / Extraction de prednisone et de prednisolone au cours des échanges plasmatiques.

Prednisone and prednisolone extraction was determined during seven sessions of plasma exchange in four patients. Each patient received 0.5 mg/kg of prednisone administered orally 2 hours before plasma exchange. Concentrations of prednisone and prednisolone were determined in blood before, every half hour during and at the end of plasma exchange. Both drugs were also determined in removed plasma, mean volume of removed plasma being 0.96 plasmatic mass. The amount of combined prednisone and prednisolone removed by plasma exchange was 1.70% of the administered prednisone dose. This quantity appears minimal and supplemental dosing of prednisone or modification of administration time would seem to be unnecessary.

[Pharmacokinetics of prednisone after oral administration in children with renal grafts. Changes induced by phenobarbital and renal insufficiency]. / Pharmacocinétique de la prednisone après dose orale chez l'enfant greffé rénal. Modifications induites par le phénobarbital et l'insuffisance rénale.

A study of blood and urinary clearance of prednisone after ingestion of a 25 mg/m2 body surface test-dose, at 8 AM, was undertaken in 20 children treated for 18 months with prednisone after renal transplant. Results show important variability between patients: the elimination half life was 2.70 +/- 0.78 hr.; Tmax time to reach Cmax was 2.10 +/- 1.08 hr.; Maximal concentration (Cmax) was 474 +/- 153 ng/ml. With respect to the dose of steroid administered, the urinary excretion of corticosteroids: 17-hydroxycorticosteroids was 12.9 +/- 7.4% and that of unchanged prednisolone 2.8 +/- 3.1%. This level was essentially achieved in the 6 first hours: 55.4 +/- 16.2% for 17-OH steroids and 87.2 +/- 14.3% for prednisolone. Two points emerge from this study: (a) Renal failure slows urinary excretion of prednisone and its metabolites, making a reduction in the doses of corticosteroids necessary at certain doses. (b) The association prednisone-phenobarbital changes the blood kinetics (excretion is faster) without a clear change in 17-OH steroid and prednisolone urinary excretion. It is associated with a decrease in graft tolerance. The kinetic changes do not seem to be the only factors implicated in the decreased therapeutic response.

In vitro formation of 25-hydroxyvitamin D3 metabolites in endometrium: dependence on the hormonal status of the rat.

Rat myometrial tissue and endometrial cells were incubated with labeled 25-hydroxyvitamin D3 ([3H-26,27] 25OHD3) for 70 min at 37 C, and the resulting metabolites were isolated by sequential Sephadex LH-20 chromatography and high performance liquid chromatography. Two peaks more polar than 25OHD3 were present on the Sephadex LH-20 chromatograms. One of these metabolites had an identical chromatographic behavior on three different HPLC systems and an identical sensitivity to periodate cleavage as biosynthetic [3H-26,27] 24,25-dihydroxyvitamin D3 ([3H-26,27]24,25-(OH)2D3]. The in vitro production of this putative 24,25-(OH)2D3 was significantly higher in castrated animals than in normal adult rats. Treatment of rats with 17 beta-estradiol and/or medroxyprogesterone acetate reversed the effect of ovariectomy on 25OHD3 conversion. The in vitro production of the putative 24,25-(OH)2D3 was low during the estrous cycle and the initial stage of pregnancy. A dramatic increase in its production was observed on days 12 and 14 of pregnancy. 25OHD3 conversion was higher in endometrium than in myometrium under every experimental condition tested. These results demonstrate the ability of rat uterine tissue to convert 25OHD3 into more polar derivatives in vitro, and show the influence of the hormonal status of the rat on this in vitro capacity.