Browsing by Author "Kriegler, A."

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    Endogenous immunoreactive digitalis-like substance in neonatal serum and placental extracts
    (Health & Medical Publishing Group, 1984) Beyers, A. D.; Spruyt, L. L.; Seifart, H. I.; Kriegler, A.; Parkin, D. P.; Van Jaarsveld, P. P.
    Therapeutic levels of digoxin in the serum of untreated neonates delivered to mothers who had not received the drug prenatally were detected by radio-immunoassay. Digoxin levels in neonates should be interpreted with care because of the unknown contribution by the endogenous digitalis-like substance (DLS) to the level of the drug. Three commercially available radio-immunoassay kits were compared with regard to their sensitivity and reproducibility in detecting the endogenous DLS. The kit from Clinical Assays (Cambridge, Mass., USA) was selected for further investigations. In a series of 35 paired samples of maternal and cord blood the average DLS values in terms of digoxin were 0.52 ± 0.07 and 0.81 ± 0.27 ng/ml respectively. This difference is statistically highly significant. In the case of infants with DLS values of 1-1.5 ng/ml in terms of digoxin, approximately 1 week was required to reach non-therapeutic digoxin levels, i.e. below 0.5 ng/ml. Gel chromatography showed that the DLS in neonatal serum was more closely associated with protein than is authentic digoxin. In placental extracts it followed the elution profile of the protein completely, but it shifted to fractions with a lower molecular weight than haemoglobin after trypsinization. The level of DLS in neonatal serum was also increased by more than half its original value by trypsinization. Proteolysis therefore seems to have a releasing effect on DLS. The molecular size of this substance is probably in the same range as that of polypeptides, since it was not dialysable from trypsinized and untreated samples through a membrane with a 22,000 dalton molecular weight cut-off point.
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    Therapeutic monitoring as an aid in rationalising aminoglycoside dosage techniques in the neonate
    (Health & Medical Publishing Group, 1987) Spruyt, L. L.; Kirsten, G. F.; Parkin, D. P.; Muller, G. J.; Kriegler, A.
    General pharmacokinetic parameters applicable to adults are not suitable in neonatal practice owing to wide interpatient variations in respect of fluid balance, renal clearance and metabolic rates. We attempted to determine whether acceptable blood levels of gentamicin or tobramycin are obtained with dosage regimens and dosage techniques which are generally recommended. Forty neonates receiving aminoglycosides were studied. After administration of the drug as a slow, constant intravenous infusion into the 'Y' connection of the infusion set, peak levels were found to be subtherapeutic. Trough levels were also very low. After administration of the same dose of gentamicin or tobramycin as a bolus into the butterfly connection of the infusion set, however, high therapeutic levels were obtained. We therefore recommend that gentamicin and tobramycin be administered as an intravenous bolus injection and that blood levels be monitored constantly in order to individualise therapy.