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14C-Mestranol (5 μc) was administered orally in a Lyndiol®**-tablet (= 5 mg lynestrenol*** + 150 μg mestranol) to four women using Lyndiol® during the lactation period shortly after delivery. The concentration of radioactivity in the plasma and the excretion of radioactivity in the urine and milk were studied. The clearance rate of radioactivity from the blood was very low. A halflife in the order of 40–60 h was found for labelled »mestranol and its metabolites«. In three cases 31–36% of the radioactivity was excreted into the urine within 5 days after oral administration of the labelled material; in the fourth patient this value was about 52 %. During a collection period of 4 days after the oral administration of the 14C-mestranol-containing tablet, 0.0002–0.013 per cent of the administered dose was excreted into the milk. These very low values were partly due to the low amounts of milk that could be collected. It was calculated that with the regular oral administration of one Lyndiol®-tablet daily, with 150 μg mestranol per tablet, about 0.03–0.06 μg (0.02–0.04 % of the administered dose) of mestranol or its metabolites might be excreted per 100 ml milk. The significance of these amounts, in view of the transfer to infants during breast-feeding, is discussed.
4-14C-Lynestrenol** was administered either orally or by intravenous injection to women using Lyndiol®*** (5 mg lynestrenol + 150 μg mestranol). In order to study the effect of the pharmaceutical form in oral administration, the radioactive progestagen was given either as the pure compound in the form of a gelatin capsule or as a tablet containing all the ingredients usually present in Lyndiol®-tablets. The concentration of radioactivity in the blood and the excretion of radioactivity in the urine and milk of lactating women were then studied. The clearance rate of radioactivity from the blood was very low. A half-life in the order of 40 h was estimated for labelled »lynestrenol and metabolites«. Within 4–5 days after oral administration of a 14C-lynestrenol containing tablet, 54–65 % of the radioactivity was excreted in the urine, whereas much smaller amounts (in the order of 15 % of the administered dose) were excreted following oral administration of 14C-lynestrenol taken in a capsule. After intravenous administration 45–56 % of the administered radioactivity was recovered in the urine excreted within 4 days after injection. After oral administration of a 14C-lynestrenol containing tablet to 3 lactating women 0.022. 0.028 and 0.088 per cent of the administered radioactivity was excreted in the milk collected during the first 5 days after administration. The results indicate that resorption may be considerably influenced by the pharmaceutical form of the orally administered compound. For oral administration of 5 mg lynestrenol daily, as a Lyndiol®-tablet, it was calculated that in the order of 1 μg (0.02 % of the administered dose) of lynestrenol or its metabolites might be excreted per 100 ml of milk. These data are discussed with regard to the amount of steroids that might be transferred to infants during breast feeding when the mothers take oral contraceptives.
In the two preceding papers of this series 1, 2 a description has been given of the reaction with KCN of various derivatives of vitamin Ba~, furtheron designated in this paper as "Bx~". It has been shown that this reaction, both with Barb and the one or several forms in which the active substance occurs in the liver (provided certain specified conditions were maintained), always leads to the formation of a substance, indistinguishable from B~ itself by its spectrum and by paper partition chromatography. That this substance actually is identical with B12 has been lately demonstrated both by BRINK et al. 3 and by our group 4, though we arrived at this conclusion along quite different lines from these investigators.The reaction with KCN allows the assay of liver-extracts, which do not contain unduly large amounts of coloured contaminations. Under the influence of KCN, not only a colorimetric determination becomes possible, but also the chromatography of the extracts, as a preparatory step to remove other interfering colours. On the other hand without KCN, chromatography frequently gives rise to several, instead of to one single red band.The object of this paper is to describe this assay, and to compare the results with those obtained with microbiological methods. Both L. lactis Dorner and L. Leichmannii were used, the first one in the "cup plate" assay described by CUTHBERTSON s and with the turbidimetric method, the second one with the turbidimetric method only. MATERIAL AND METHODS MaterialThe liver fractions used ior the chemical determinations were all prepared by N.V. Organon. They contained about 0.2 % of Bls and mostly brownish and yellow impurities in amounts sufficient to give the powders a pink to buff eoloured appearance.Some samples ot commercial products, obtained in the open market, and some very crude liverextracts were included in the microbiological assays. The activity of these products has not been Re/erenoes p. 65.
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