Final answer:
Trimetaphan is a sympatholytic drug that interrupts the function of the sympathetic nervous system and is incompatible with thiopentone, a barbiturate anesthetic.
Step-by-step explanation:
The question pertains to Trimetaphan, a drug that affects the sympathetic nervous system. Trimetaphan is a sympatholytic drug, which means it interrupts the function of the sympathetic nervous system. This drug acts as a ganglionic blocker and is used to induce rapid, short-term lowering of blood pressure during surgery. Given the options provided in the question, the most accurate answer is that Trimetaphan (B) is incompatible with thiopentone. Thiopentone is a barbiturate anesthetic, and Trimetaphan can potentiate its hypotensive effect. It is important to avoid combination of these drugs to prevent excessive hypotension. Trimetaphan does not stimulate the sympathetic ganglion, so (C) is incorrect. While the ability of Trimetaphan to cross the blood-brain barrier is not well-documented, its primary site of action is outside the central nervous system, indicating option (A) is less relevant.