Neonatal theophylline intoxication: pharmacokinetics and clinical evaluation.

The pharmacokinetics of theophylline and its metabolites, caffeine, 1,3-dimethyluric acid, 1-methyluric acid and 3-methylxanthine were studied in a 5-day old 1.3 kg premature neonate who accidentally received 180 mg theophylline in 26 h during treatment for bradycardia. Tachycardia, hyperventilation, increased diuresis, central nervous system excitation, an increase in blood glucose concentrations followed by a prolonged decrease and hypercalcaemia were the predominant clinical and laboratory manifestations. The patient responded to supportive care and survived without sequelae. The concentration time course of theophylline and its metabolites in plasma and the pattern of urinary and gastric elimination were determined over 95 h. Theophylline showed, in contrast to its metabolites, a log linear decline in plasma. Elimination of theophylline and caffeine, calculated from their urinary excretion rates, were both exponential during the entire observation period. Urine flow dependence of renal clearance was obvious for theophylline and caffeine. Implications of theophylline disposition in neonates are discussed with special regard to theophylline poisoning.

[Taurine supplementation in cystic fibrosis (CF): effect on vitamin E absorption kinetics]. / Taurin-Supplementierung bei Cystischer Fibrose (CF): Einfluss auf die Absorptionskinetik von Vitamin E.

Oral vitamin E (Vit.E) bioavailability is reduced in CF patients especially in case of malnourishment. Both exocrine pancreatic insufficiency and an altered bile acid composition showing an elevated glycine taurine ratio of conjugated bile acids which is due to excessive loss of bile acids in the stools may contribute to this observation. Because taurine supplementation reduces the glycine/taurine ratio of bile acids in duodenal juice of CF-patients it was the objective of this study to evaluate the effect of taurine supplementation on Vit.E absorption kinetics. Oral Vit.E tolerance tests (50 mg/kg) were performed before and after 3 months of taurine supplementation (30 mg/kg/day) in 11 CF patients (ages 7 to 22 years) under fasting conditions. Bodyweight and or weight for height of all patients were below the 25th percentile. Doses of all medications except antibiotics were kept unchanged during the study. Any additional Vit.E supplementation was stopped 14 days prior to each test. Serum Vit.E levels were measured over a 24 hour period. Determination of serum Vit.E concentrations was performed with a HPLC fluorescence technique. The glycine/taurine ratio in serum served as compliance parameter and dropped in all but one patients. Baseline Vit.E concentrations and serum Vit.E/total lipids ratios in serum considered as parameters of the Vit.E status increased significantly. Both the maximal Vit.E concentrations in serum and the areas under the oral absorption curves showed a significant increase with taurine supplementation. This study shows that the Vit.E status of malnourished CF patients can be improved with taurine supplementation due to improved Vit.E absorption kinetics.(ABSTRACT TRUNCATED AT 250 WORDS)

[Effect of nutritional status on absorption kinetics of vitamin E in mucoviscidosis]. / Einfluss des Ernährungsstatus auf die Absorptionskinetik von Vitamin E bei Mukoviszidose (CF).

Exocrine pancreatic insufficiency with varying severity must be anticipated in 85-95% of CF patients. It leads to fat maldigestion and malabsorption of the liposoluble vitamins - A, D, E, K - and fecal loss of fat. In general, supplementation with fat-soluble vitamins is recommended in CF patients. In this study an oral vitamin E tolerance test (100 mg/kg bodyweight) was performed in 5 healthy adult volunteers to elaborate a vitamin E absorption kinetics and additionally in CF patients on medication with pancreatic enzymes to evaluate the absorption of vitamin E. 19 CF patients (ages 4 to 19 years) were studied after cessation of any additional vitamin E supplementation for 7 days. Vitamin E serum concentrations were sampled over a 72 hour period. Serum vitamin E determinations were performed with a HPLC-fluorescence technique. The kinetics of Vitamin E in healthy volunteers can be described with an open 2 compartment model. CF patients revealed consistently an altered kinetics of absorption of vitamin E, which was not compatible with this model. Baseline (c*) and maximal serum concentrations (cmax) of vitamin E as well as the area outer the oral absorption curve (AUC) correlated with the nutritional status expressed by bodyweight percentiles in CF patients. The results of this study show that in normal weight CF patients on pancreatic enzymes medication vitamin E depletion is unlikely.(ABSTRACT TRUNCATED AT 250 WORDS)

[Pharmacokinetics of combined antibiotic therapy in the newborn infant]. / Pharmakokinetik der kombinierten Antibiotikatherapie beim Neugeborenen.

In 66 newborn infants (AGA) suffering from septicemia concentration time courses of gentamicin, ampicillin and cefotaxim were determined to perform and an individual drug monitoring. Gentamicin was analysed from capillar blood samples using EMIT, Ampicillin and Cefotaxim by HPLC-technique. Volumes of distribution, apparent elimination half lives, maximum -, minimum and steady state concentrations were calculated using digital iteration programs. Based on a fixed dose regimen the kinetic parameters of gentamicin were extremely variable. To achieve a median steady state concentration of 3 micrograms/ml gentamicin in serum corrections from -17% to +110% of the foregoing dose were necessary. With 100 mg/kg ampicillin or cefotaxim per day sufficient concentrations in serum were reached. But in some patients a dosage of 5-7 mg/kg/d of gentamicin is too low, while others show concentrations near to the toxic levels. By a combination of gentamicin plus ampicillin pharmacokinetic parameters are not influenced; while if gentamicin is combined with cefotaxim the apparent elimination halflife of gentamicin (beta-slope) is significantly reduced. Therefore an individual drug monitoring of drugs with a small therapeutic range, for example gentamicin, is necessary to optimize therapeutic results.

Influence of food intake on bioavailability of theophylline in premature infants.

16 premature infants suffering from neonatal apnoea received orally an aqueous solution of theophylline 5 mg/kg bodyweight under fasting conditions and immediately before a milk feed. Bioavailability up to 7 h after administration was determined from the serum concentration-time course. The rate of absorption was significantly decreased if the drug was given with food; mean maximum serum concentrations were reached after 4.7 h instead of 1.6 h under fasting conditions. The area under the curve did not differ between the two patient groups which indicates that only the rate but not the amount of absorption was affected by food intake. The influence of feeding on the rate of absorption of theophylline by premature infants, which is more pronounced than in adults, can be related to particular functional factors in the gastrointestinal tract during the neonatal period.