Terlipressin can be used for hematemesis from oesophageal varices. The action is mediated by:
## Core Concept
Terlipressin is a synthetic analogue of vasopressin, used primarily for its vasoconstrictive properties. It acts on blood vessels to cause vasoconstriction, which helps in reducing blood flow to the esophageal varices, thereby controlling bleeding. This action is crucial in the management of acute variceal hemorrhage.
## Why the Correct Answer is Right
The correct answer, **V1 receptors**, is right because terlipressin's action in controlling bleeding from esophageal varices is primarily mediated through vasoconstriction. This effect is achieved by stimulating **V1 receptors**, specifically **V1a receptors**, which are found on vascular smooth muscle cells. Activation of these receptors leads to vasoconstriction, reducing splanchnic blood flow and subsequently decreasing the pressure in the varices.
## Why Each Wrong Option is Incorrect
- **Option A: β1 receptors** - Incorrect because β1 receptors are primarily involved in cardiac effects, such as increased heart rate and contractility, which is not the primary mechanism by which terlipressin exerts its effect on esophageal varices.
- **Option B: V2 receptors** - Incorrect because V2 receptors are primarily involved in the antidiuretic effect of vasopressin, promoting water reabsorption in the kidneys. This action does not contribute to the vasoconstrictive effect needed to control bleeding from varices.
- **Option D: α1 receptors** - While α1 receptors are also involved in vasoconstriction, terlipressin's primary action in this context is more specifically related to **V1 receptors**. However, it's worth noting that the end effect (vasoconstriction) can involve various receptors, but terlipressin's effect is notably described through V1 receptor activation.
## Clinical Pearl / High-Yield Fact
A key point to remember is that terlipressin is used in the setting of acute variceal hemorrhage because it effectively reduces splanchnic blood flow and portal pressure through vasoconstriction, thereby helping to control bleeding. It's a preferred agent because it has a longer duration of action compared to vasopressin, making it more convenient for clinical use.
## Correct Answer: C. V1 receptors