Trimetaphan camsilate (INN) or trimethaphan camsylate (USAN), trade name Arfonad, is a sympatholytic drug used in rare circumstances to lower blood pressure.

The ciliary muscle of the eye functions to round the lens for accommodation and is controlled mainly by parasympathetic system input.

With administration of a ganglion-blocking drug, the ciliary muscle cannot contract (cycloplegia) and the patient loses the ability to focus their eyes.

The mechanism behind it is unknown, as trimethaphan does not appear to block neuromuscular transmission, and respiratory arrest is not an expected consequence of ganglionic blockage.

[2] The therapeutic uses of trimetaphan are very limited due to the competition from newer drugs that are more selective in their actions and effects produced.