Which pharmacologic agent decreases uterine contraction in a dose-dependent fashion?

Which pharmacologic agent decreases uterine contraction in a dose-dependent fashion?

• A. Barbiturates
• B. Diazepam
• C. Ketamine
• D. Nitrous oxide

Answer: (A)

Some drugs can relax the uterus in proportion to how much you give them, meaning the more you dose, the more the myometrium relaxes. Barbiturates depress the central nervous system as the dose increases, which dampens the signals that normally stimulate uterine contractions. This results in a dose-dependent reduction in myometrial activity, making contractions weaker as the dose goes up. Diazepam also relaxes the patient but doesn’t reliably produce a dose-dependent decrease in uterine contractions. Ketamine tends to maintain or increase uterine tone because it can stimulate sympathetic activity, not relax it. Nitrous oxide, on the other hand, doesn’t reliably affect uterine contractility in a dose-dependent way. In practice, barbiturates aren’t used as routine tocolytics, but their greater CNS depression at higher doses can translate to reduced uterine activity in a dose-related fashion.

Some drugs can relax the uterus in proportion to how much you give them, meaning the more you dose, the more the myometrium relaxes. Barbiturates depress the central nervous system as the dose increases, which dampens the signals that normally stimulate uterine contractions. This results in a dose-dependent reduction in myometrial activity, making contractions weaker as the dose goes up. Diazepam also relaxes the patient but doesn’t reliably produce a dose-dependent decrease in uterine contractions. Ketamine tends to maintain or increase uterine tone because it can stimulate sympathetic activity, not relax it. Nitrous oxide, on the other hand, doesn’t reliably affect uterine contractility in a dose-dependent way. In practice, barbiturates aren’t used as routine tocolytics, but their greater CNS depression at higher doses can translate to reduced uterine activity in a dose-related fashion.