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The pharmacokinetics of oxytocin as they apply to labor induction

      Abstract

      OBJECTIVE: Our purpose was to determine the relationship among plasma oxytocin levels, metabolic clearance rate of oxytocin, and uterine activity in gravid women undergoing labor induction. STUDY DESIGN: Ten women receiving oxytocin for labor induction and agreeing to participate had blood sampled before initiation of oxytocin and at different levels of uterine pressure. Samples were analyzed with 200 μl extracts from 1 ml of plasma with an oxytocin radioimmunoassay. The intraassay coefficient of variation was <3%. Sensitivity of the assay was 1.5 pg/ml. Pharmacokinetic parameters including plasma levels and metabolic clearance rates were calculated. Data were analyzed with the paired t test and linear and logistic regression. RESULTS: Mean oxytocin levels and metabolic clearance rates were 26.6 pg/ml and 7.97 ml/min. There was no correlation between changes in oxytocin level and metabolic clearance rate. Increases in infusion rates were correlated with increases in oxytocin levels (r = 0.71, p < 0.001). Cervical dilatation and uterine contraction pressures did not correlate with oxytocin levels. CONCLUSION: Peripheral plasma levels of oxytocin may not accurately reflect uterine activity or progress in labor. Plasma levels of oxytocin may merely reflect the rate of oxytocin infusion. (AM J OBSTET GYNECOL 1996;174:1590-3.)

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      References

        • Du Vigneaud V
        • Ressler C
        • Swan JM
        • Roberts CW
        • Katsoyannis PG
        • Gordon S
        The synthesis of oxytocin.
        J Am Chem Soc. 1953; 75: 4879-4880
        • Satin AJ
        • Leveno KJ
        • Sherman ML
        • Brewster DS
        • Cunningham FG
        High- versus low-dose oxytocin for labor stimulation.
        Obstet Gynecol. 1992; 80: 111-116
        • American College of Obstetricians and Gynecologists
        Induction and augmentation of labor.
        American College of Obstetricians and Gynecologists, Washington, DC1991 (Technical bulletin no 157.)
        • American College of Obstetricians and Gynecologists
        Induction of labor.
        American College of Obstetricians and Gynecologists, Washington, DC1987 (Technical bulletin no 110.)
        • Seitchik J
        • Amico J
        • Robinson AG
        • Castillo M
        Oxytocin augmentation of dysfunction labor, IV: oxytocin pharmacokinetics.
        AM J OBSTET GYNECOL. 1984; 150: 225-228
        • O'Driscoll K
        • Foley M
        • MacDonald D
        Active management of labor as an alternative to cesarean section for dystocia.
        Obstet Gynecol. 1984; 63: 485-490
        • Lopez-Zeno JA
        • Peaceman AM
        • Adashek JA
        • Socol ML
        A controlled trial of a program for the active management of labor.
        N Engl J Med. 1992; 326: 450-454
      1. Labor and delivery operating procedure #160-90. Wilford Hall Medical Center, Lackland Air Force Base, Texas1993
        • Satin AJ
        • Leveno KJ
        • Sherman ML
        • McIntire D
        High dose oxytocin - 20 versus 40 minute dosage intervals.
        Obstet Gynecol. 1994; 83: 234-238
        • Thornton S
        • Davison JM
        • Baylis PH
        Effect of human pregnancy on metabolic clearance rate of oxytocin.
        Am J Physiol. 1990; 259: R21-R24
        • Weitzman RE
        • Theodore HG
        • Fisher DA
        The effect of hemorrhage and hypertonic saline upon plasma oxytocin and arginine vasopressin in conscious dogs.
        Endocrinology. 1978; 103: 2154-2160
        • Leake RD
        • Weitzman RE
        • Glatz TH
        • Fisher DA
        Plasma oxytocin concentrations in men, nonpregnant women, and pregnant women before and during spontaneous labor.
        J Clin Endocrinol Metab. 1981; 53: 730-733
        • Rydén G
        • Sjöholm I
        The metabolism of oxytocin in pregnant and non-pregnant women.
        Acta Obstet Gynecol Scand. 1971; 9: 39
        • Leake RD
        • Weitzman RE
        • Fisher DA
        Pharmacokinetics of oxytocin in the human subject.
        Obstet Gynecol. 1980; 56: 701-704
        • Caldeyro-Barcia R
        • Poseiro JJ
        Oxytocin and contractility of the pregnant human uterus.
        Ann N Y Acad Sci. 1959; 75: 813-830
        • Satin AJ
        • Leveno KJ
        • Sherman ML
        • McIntire DD
        Factors affecting the dose response to oxytocin for labor stimulation.
        AM J OBSTET GYNECOL. 1992; 166: 1260-1261