Clinically relevant concentrations of dexmedetomidine may reduce oxytocin-induced myometrium contractions in pregnant rats

BACKGROUND: Recently, there have been some trials to use dexmedetomidine in the obstetric field but concerns regarding the drug include changes in uterine contractions after labor. We aimed to evaluate the effects of dexmedetomidine on the myometrial contractions of pregnant rats. METHODS: In a pilot study, the contraction of the myometrial strips of pregnant Sprague-Dawley rats in an organ bath with oxytocin at 1 mU/ml was assessed by adding dexmedetomidine from 10(-6) to 10(-2) M accumulatively every 20 min, and active tension and the number of contractions were evaluated. Then, changes in myometrial contractions were evaluated from high doses of dexmedetomidine (1.0 × 10(-4) to 1.2 × 10(-3) M). The effective concentrations (EC) for changes in uterine contractions were calculated using a probit model. RESULTS: Active tension and the number of contractions were significantly decreased at 10(-3) M and 10(-4) M dexmedetomidine, respectively (P < 0.05). A complete loss of contractions was seen at 10(-2) M. Dexmedetomidine (1.0 × 10(-4) to 1.2 × 10(-3) M) decreased active tension and the number of contractions in a concentration-dependent manner. The EC(95) of dexmedetomidine for inhibiting active tension and the number of contractions was 5.16 × 10(-2) M and 2.55 × 10(-5) M, respectively. CONCLUSIONS: Active tension of the myometrium showed a significant decrease at concentrations of dexmedetomidine higher than 10(-3) M. Thus, clinical concentrations of dexmedetomidine may inhibit uterine contractions. Further research is needed for the safe use of dexmedetomidine in the obstetrics field.