RX 67668 is a muscle relaxant used to relieve skeletal muscle fatigue. RX 67668 is an effective cholinesterase inhibitor (IC50: 5 μM for both acetylcholinesterase and butyrylcholinesterase). RX 67668 can reverse the neuromuscular blockade induced by D-tubocurarine.

AChE:5 μM, BChE:5 μM

RX 67668 (1-4 mg/kg; i.p.) decreases by half the dose of methacholine necessary to produce red tears, whilst RX 67668 (7-2 mg/kg s.c.) is necessary to reduce the pupil diameter of the mouse to 50% of the control value. RX 67668 (0.3-1.0 mg/kg; i.v.) is effective in reversing tubocurarine-induced muscle blockade [1].