Treatment of fetal tachycardia with sotalol: transplacental pharmacokinetics and pharmacodynamics.
OBJECTIVE
The aim of this study was to investigate the pharmacokinetics and pharmacodynamics of sotalol in the treatment of fetal tachycardia.


BACKGROUND
Maternally administered, intrauterine therapy of fetal tachycardia is dependent on the transplacental passage of the antiarrhythmic agent.


METHODS
In a prospective study of patients treated for fetal tachycardia with sotalol, concentrations of sotalol were determined in maternal and umbilical blood and in amniotic fluid, and the relationship between these concentrations and the occurrence of conversion to sinus rhythm was investigated.


RESULTS
Eighteen fetal patients were studied, nine with atrial flutter and nine with supraventricular tachycardia. Fourteen were treated with sotalol; 13 converted to sinus rhythm, of whom 2 relapsed. There was one intrauterine death. Four patients were treated with sotalol and digoxin, of whom two were treated successfully. Mean birth weight was 3,266 g. The daily maternal sotalol dose was linearly related to the maternal plasma concentration. The mean fetal/maternal sotalol plasma concentration was 1.1 (range 0.67 to 2.87, SD 0.63), and the mean amniotic fluid/fetal blood ratio of sotalol was 3.2 (range 1.28 to 5.8, SD 1.4). The effectiveness of sotalol therapy could not be extrapolated from maternal blood levels.


CONCLUSIONS
Sotalol is a potent antiarrhythmic agent in the treatment of fetal tachycardia. The placental transfer is excellent. Sotalol accumulates in amniotic fluid but not in the fetus itself. Therefore it seems that renal excretion in the fetus is efficient and greater than the oral absorption by fetal swallowing. The maternal blood level is not a reliable predictor of the chances of success of therapy. Sotalol is not associated with fetal growth restriction.
Oudijk
Martijn A
MA
Department of Obstetrics, University Medical Center Utrecht, The Netherlands. m.oudijk@azu.nl
Ruskamp
Jopje M
JM
Ververs
F F Tessa
FF
Ambachtsheer
E Barbara
EB
Stoutenbeek
Philip
P
Visser
Gerard H A
GH
Meijboom
Erik J
EJ
D000653:Amniotic Fluid / Q000737:chemistry; D000889:Anti-Arrhythmia Agents / Q000627:therapeutic use*; D004305:Dose-Response Relationship, Drug; D005260:Female; D005312:Fetal Blood / Q000737:chemistry; D005315:Fetal Diseases / Q000188:drug therapy*; D006801:Humans; D008431:Maternal-Fetal Exchange; D010920:Placenta / Q000502:physiology; D011247:Pregnancy; D011446:Prospective Studies; D013015:Sotalol / Q000627:therapeutic use*; D013610:Tachycardia / Q000150:complications / Q000188:drug therapy*
D000889:Anti-Arrhythmia Agents; D013015:Sotalol