Caritis S N, Venkataramanan R, Cotroneo M, Smith M, Chiao J P, Habucky K
Department of Obstetrics and Gynecology, University of Pittsburgh School of Medicine, PA.
Am J Obstet Gynecol. 1990 May;162(5):1215-9. doi: 10.1016/0002-9378(90)90021-x.
To define the pharmacokinetics and pharmacodynamics of ritodrine after intramuscular injection, we administered 5 or 10 mg ritodrine into the gluteus or deltoid muscles of 12 pregnant volunteers. Six women received 5 mg and six received 10 mg into each muscle group on different days. We withdrew blood samples before and 12 times in the 6 hours after ritodrine injection. Blood pressure and heart rate were recorded at each time. Ritodrine was measured by high-performance liquid chromatography. Peak ritodrine concentrations (mean +/- SD) after a single 5 mg injection in the deltoid or gluteus were 38 +/- 13 and 26 +/- 8 ng/ml, respectively. After a 10 mg dose in the deltoid or gluteus, peak concentrations were 59 +/- 30 and 47 +/- 22 ng/ml, respectively. Although higher, the peak plasma concentrations after injections into the deltoid were not significantly greater than those after injection into the gluteus. None of the pharmacokinetic parameters differed according to dose or injection site. The pharmacodynamic effects of ritodrine were unaffected by injection site, but ritodrine caused a dose-related increase in heart rate and systolic blood pressure and a dose-related decrease in diastolic blood pressure. After a 10 mg injection, the maximal changes in heart rate, systolic, and diastolic blood pressure were 22%, 10%, and 19%, respectively. However, mean blood pressure was not altered by either the 5 or 10 mg dose. These findings indicate that there are few differences in pharmacokinetic parameters between deltoid and gluteal injection of ritodrine. The single intramuscular injection of 5 or 10 mg ritodrine results in labor-inhibiting concentrations with clinically insignificant cardiovascular effects.
为确定肌内注射利托君后的药代动力学和药效学，我们将5或10毫克利托君注射到12名怀孕志愿者的臀肌或三角肌中。6名女性在不同日期分别在每个肌肉组中接受5毫克，另外6名接受10毫克。在注射利托君前及注射后6小时内抽取12次血样。每次都记录血压和心率。利托君通过高效液相色谱法测定。单次5毫克利托君注射到三角肌或臀肌后的峰值浓度（平均值±标准差）分别为38±13和26±8纳克/毫升。在三角肌或臀肌中注射10毫克剂量后，峰值浓度分别为59±30和47±22纳克/毫升。尽管三角肌注射后的血浆峰值浓度较高，但并不显著高于臀肌注射后的浓度。药代动力学参数均不因剂量或注射部位而有所不同。利托君的药效学作用不受注射部位影响，但利托君会导致心率和收缩压呈剂量相关增加，舒张压呈剂量相关降低。注射10毫克后，心率、收缩压和舒张压的最大变化分别为22%、10%和19%。然而，5毫克或10毫克剂量均未改变平均血压。这些发现表明，三角肌注射和臀肌注射利托君后的药代动力学参数几乎没有差异。单次肌内注射5或10毫克利托君会产生抑制宫缩的浓度，且对心血管系统的影响在临床上无显著意义。
