Is monitoring plasma levels of netilmicin necessary in neonates?

Thirty-two neonates were treated with netilmicin 3 mg/kg every 12 h by IV infusion for 30 min for suspected infections, colonization, or proven infections. Pharmacokinetic studies were performed in order to define the situations in which monitoring of plasma levels would be appropriate. Mean plasma levels were within the therapeutic range and did not differ in fullterms and preterms. In the 4 children who had 2 successive pharmacokinetic studies, plasma levels were increased between H1 and H5 at the second evaluation due to netilmicin accumulation. Plasma half-life was longer in proven infections and seemed to decrease in preterms with increased gestational age. These results suggest that the dosage schedule should be left inchanged, but that administration time should be reduced from 30 to 20 min and that peak and trough plasma levels should be measured only in proven infections, in very premature babies (gestational age less than 33 wk), and during netilmicin treatment longer than 5 d.

Effect of tamoxifen on the pharmacokinetics of theophylline in rats.

The effect of tamoxifen on the pharmacokinetics of theophylline was investigated in male Sprague-Dawley rats. The oral administration of tamoxifen at a dose equal to 40 mg kg-1 48 h before the intravenous injection of theophylline 10 mg kg-1, significantly (P < 0.05) increased the clearance of theophylline by 39%, with no apparent effect on the volume of distribution. As a consequence, the elimination half-life of theophylline was significantly (P < 0.05) shortened in the tamoxifen-treated rats (3.56 +/- 0.39 h vs 5.25 +/- 0.48 h) as well as its mean residence time (5.04 +/- 0.60 h vs 7.50 +/- 0.75 h). Although these data cannot be directly extrapolated to the clinical situation, they provide experimental support to suggest that more attention should be paid to the potential risk of pharmacokinetic interactions in the presence of tamoxifen.

[Study of residual levels of delayed-action neuroleptics]. / Etude des taux résiduels de neuroleptiques à action prolongée.

Pharmacokinetics of the depot antipsychotics are unclear and mainly depend on releasing from the depot site (according to a "flip-flop" model). Few data are available on residual plasma concentrations of those drugs. We have practiced 38 blood determinations among 15 patients treated by long-acting neuroleptics (10 by fluphenazine decanoate, 4 by flupentixol decanoate and 1 by pipotiazine palmitate). Radio Receptor Assay method was used (based on competition for dopamine receptors binding), with results expressed as chlorpromazine equivalents. They showed; a wide interindividual variability; considering each subject, intraindividual variability is attenuated; blood measurements are mainly higher than therapeutic ranges (especially for patients on fluphenazine decanoate). Those results might involve that some patients are overdosed, but other studies are needed in this way.

[Are theophylline determinations useful to the clinician during treatment with a sustained-release form of theophylline?]. / Les dosages de théophylline sont-ils utiles au clinicien au cours des traitements par théophylline à libération continue?

The aims of the study were the correlation between dosage and plasmatic levels of slow release theophylline and the reason for dosage adjustment. 64 pharmacokinetic studies were performed in 58 asthmatic children between 17 months and 16 years. Plasmatic levels of theophylline were performed by fluoroimmunology technique at H0 (before the dose) 2 (H2), 4 (H4), 6 (H6) and 8 (H8) hours after the dose of slow release theophylline. The best correlation between dose and plasmatic levels were observed at H4 and H6 for Armophylline and Euphylline respectively. Dosage adjustment were based both upon clinical state and plasmatic levels in 55 cases. In 9 cases the modification of dose were decided only because of plasmatic levels out the therapeutic range. The authors proposed a schema of dosage modifications based upon clinical state; plasmatic levels must be used as a guide for dose adjustment in patients clinically uncontrolled.