Dose of clonidine in suppression test done for pheochromocytoma is?
**Core Concept**
Clonidine is used in the suppression test for pheochromocytoma to assess the functional status of the tumor. This test relies on the principle that tumors producing excess catecholamines will not suppress their production in response to clonidine, whereas normal adrenal glands or non-functioning pheochromocytomas will respond to the alpha-2 adrenergic agonist by reducing catecholamine secretion.
**Why the Correct Answer is Right**
The correct dose of clonidine for this suppression test is 2 mg. Clonidine acts by stimulating alpha-2 adrenergic receptors in the central nervous system, which in turn inhibits the release of catecholamines from the adrenal medulla. In patients with functioning pheochromocytomas, the tumors do not respond to clonidine by reducing catecholamine production, leading to a lack of suppression in the test.
**Why Each Wrong Option is Incorrect**
* **Option A:** This option is incorrect because the dose of clonidine is not sufficient to elicit a response in the suppression test.
* **Option B:** This option is incorrect because the dose of clonidine is too high and may cause hypotension or other adverse effects.
* **Option D:** This option is incorrect because the dose of clonidine is not standard for the suppression test.
**Clinical Pearl / High-Yield Fact**
It is essential to remember that a negative suppression test does not rule out pheochromocytoma, as some tumors may not respond to clonidine. A positive test, however, can help confirm the diagnosis and guide further management.
**Correct Answer: C. 2 mg**