Betamethasone in pregnancy: influence of maternal body weight and multiple gestation on pharmacokinetics.
OBJECTIVE
The goals of the study were to estimate the pharmacokinetic parameters of standard dose betamethasone in a large obstetrics population and evaluate the effect of maternal body size and multiple gestation on the pharmacokinetic parameters and their observed variability.


METHODS
This was a prospective pharmacokinetic study. Liquid chromatography mass spectrometry was used to measure betamethasone plasma concentrations. Pharmacokinetic parameters and significant clinical covariates were estimated with mixed effect modeling. Bootstrap analysis confirmed validity of the model.


RESULTS
Two hundred seventy-four blood samples from 77 patients were obtained. The greatest effect on pharmacokinetic variability was observed with maternal lean body weight (LBW). The relationship between the pharmacokinetic parameters and LBW remained linear over a wide range of maternal body sizes. Multiple gestations did not affect the pharmacokinetic parameters.


CONCLUSIONS
Individualization of betamethasone dosing by maternal LBW reduces variability in drug exposure. Mutiple gestations do not require betamethasone dosing adjustment, because pharmacokinetics are the same as singleton gestations.
Della Torre
Micaela
M
Division of Maternal Fetal Medicine, Department of Obstetric and Gynecology, University of Illinois at Chicago, Chicago, IL, USA. 3micaela@gmail.com
Hibbard
Judith U
JU
Jeong
Hyunyoung
H
Fischer
James H
JH
D000293:Adolescent; D000328:Adult; D019540:Area Under Curve; D001499:Bayes Theorem; D001623:Betamethasone / Q000097:blood / Q000493:pharmacokinetics*; D015992:Body Mass Index; D001835:Body Weight; D002853:Chromatography, Liquid; D005260:Female; D005938:Glucocorticoids / Q000097:blood / Q000493:pharmacokinetics*; D006801:Humans; D008875:Middle Aged; D011247:Pregnancy; D011272:Pregnancy, Multiple; D011446:Prospective Studies; D053719:Tandem Mass Spectrometry
D005938:Glucocorticoids; D001623:Betamethasone
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