**Question:** Anesthetic agent/s which have tocolytic effect are:

A. Morphine
B. Propofol
C. Diazepam
D. Thiopentone

**Correct Answer:** **D. Thiopentone**

**Core Concept:** Tocolysis is the medical intervention aimed at preventing or delaying preterm labor (labor occurring before 37 completed weeks of pregnancy). Tocolytic drugs suppress the uterine contractions and prolong pregnancy.

**Why the Correct Answer is Right:** Thiopentone is a barbiturate anesthetic agent that has tocolytic properties. It works by inhibiting the release of prostaglandins, which are responsible for uterine contractions during labor. By suppressing prostaglandin release, thiopentone helps in delaying preterm labor and prolonging pregnancy.

**Why Each Wrong Option is Incorrect:**

A. Morphine: Morphine is an opioid analgesic used for pain relief. Although it can cause uterine relaxation, its tocolytic effect is less potent compared to thiopentone.

B. Propofol: Propofol is an intravenous anesthetic agent used for sedation and anesthesia. Although it can cause uterine relaxation, its tocolytic effect is less potent than thiopentone.

C. Diazepam: Diazepam is a benzodiazepine medication used for its anxiolytic, sedative, and muscle relaxant properties. While it can cause uterine relaxation, its tocolytic effect is weaker than thiopentone.

**Clinical Pearl:** Thiopentone is often chosen as a tocolytic agent due to its potent and reliable tocolytic effect. In clinical practice, thiopentone is usually administered as an intravenous infusion at a rate of 1-2 mg/kg/h for 24-48 hours.

In summary, while morphine, propofol, and diazepam can cause uterine relaxation, thiopentone is the correct answer as it exhibits the most potent tocolytic effect.