Stability of fat-soluble vitamins A (retinol palmitate), E (tocopherol acetate), and K1 (phylloquinone) in total parenteral nutrition at home.

Our purpose was to extend previous studies of the stability of vitamins A (retinol palmitate), E (tocopherol acetate), and K1 (phylloquinone) to total parenteral nutrition at-home (TPNH) admixtures. First, stability over 20 days was tested. Experimental conditions included presence or absence of lipids, presence or absence of trace elements, and storage in a glass bottle or in a single or multi-layer plastic bag (ethylene vinyl acetate, polyvinyl chloride, Stedim 5, and Stedim 6). The 20-day storage studies were conducted at 4 degrees C or at ambient air temperature. The second part of the study consisted of exposing to natural light TPNH admixtures with or without lipids, but with trace elements, in the same containers (except polyvinyl chloride). Finally, a clinical situation of TPNH was simulated with a TPNH admixture prepared 11 days before the test in a Stedim 6 plastic bag and stored at 4 degrees C in total darkness. For vitamins A, E, and K1, we observed good stability for 20 days; the final concentrations ranged from 75% to 100% of initial concentrations whatever the conditions studied. It appears that there is no significant difference of action between all containers and that the presence or absence of lipids and trace elements in admixtures stored at 4 degrees C or ambient temperature makes no difference. With exposure to sunlight, vitamin losses were 100% at 3 hours for vitamin A and 50% for vitamin K1; vitamin E concentrations were unchanged after 12 hours of experiment.(ABSTRACT TRUNCATED AT 250 WORDS)

On-line measurements of 13C enrichments in rat breath. Non-invasive method for in vivo study of drug enzymatic induction.

A differential kinetic study of 13CO2 enrichment of breath after the intake of specific 13C-labelled substrates and co-administration of a drug allows the drug's ability for enzyme induction to be evaluated in vivo. A method and a gas chromatograph-isotope ratio mass spectrometer device for on-line measurements of 13CO2 enrichment in the breath of small animals are described. This system allows on-line breath sample collection from a metabolic cage, purification by gas chromatography, determination of CO2 by thermal conductivity detection and measurement of 13CO2 enrichment by isotope ratio mass spectrometry. Two protocols for phenobarbital-inducible P450 and 3-methylcholanthrene-inducible P1-450 isoenzymes are described.