[Pharmacokinetics and materno-fetal influence of ritodrine hydrochloride during the continuous treatment of threatened premature labor].
The cardiovascular and metabolic effects of ritodrine hydrochloride on the mother and fetus were investigated during the 28-day and/or longer continuous treatment of threatened premature labor. Concentrations of ritodrine in maternal venous blood during the treatment, and placental transfer of the drug into the fetal circulation and amniotic fluid were also determined to ascertain the effectiveness and safety of the drug. Seventeen volunteer patients at 27-34 weeks of gestation were given a total dose of 2,850-7,350mg of ritodrine intravenously at a mean infusion rate of 72.9 micrograms/min for 28-66 days, when the maternal serum concentration of ritodrine was maintained at approximately 200ng/ml throughout the treatment period. A significant but slight increase in the maternal heart rate and serum glucose, and a slight fall in maternal blood pressure were observed during ritodrine infusion. The fetal heart rate did not change significantly. Although ritodrine also produced decreases in the red blood cell count, hemoglobin and hematocrit, these changes were transient and recovered to the control level thereafter. The ratios of umbilical venous blood and the amniotic fluid concentration of ritodrine to maternal venous concentrations determined at cesarean section were 0.68 and 1.64, respectively, suggesting that a gradual accumulation of placentally transferred ritodrine may occur when long-term continuous infusion is carried out. There were no noticeable drug-related findings in mothers and newborns during and after labor. These results indicate that threatened premature labor may be well effectively controlled by ritodrine without severe side-effects on the mother or fetus in treatment for along period.
Fujimoto
S
S
Department of Obstetrics and Gynecology, Hokkaido University School of Medicine, Sapporo.
Akahane
M
M
Tanaka
T
T
Hanatani
K
K
D000328:Adult; D000653:Amniotic Fluid / Q000378:metabolism; D001786:Blood Glucose / Q000378:metabolism; D001794:Blood Pressure / Q000187:drug effects; D004341:Drug Evaluation; D004361:Drug Tolerance; D005260:Female; D005312:Fetal Blood / Q000378:metabolism; D005333:Fetus / Q000187:drug effects*; D006339:Heart Rate / Q000187:drug effects; D006340:Heart Rate, Fetal / Q000187:drug effects; D006801:Humans; D007262:Infusions, Intravenous / Q000379:methods; D008297:Male; D008431:Maternal-Fetal Exchange; D007752:Obstetric Labor, Premature / Q000188:drug therapy* / Q000378:metabolism; D010920:Placenta / Q000378:metabolism; D011247:Pregnancy; D012312:Ritodrine / Q000008:administration & dosage / Q000493:pharmacokinetics* / Q000627:therapeutic use
D001786:Blood Glucose; D012312:Ritodrine