Description a synthetic nondepolarizing blocking drug. the actions of gallamine triethiodide are similar to those of tubocurarine, but this agent blocks the cardiac vagus and may cause sinus tachycardia and, occasionally, hypertension and increased cardiac output. it should be used cautiously in patients at risk from increased heart rate but may be preferred for patients with bradycardia.mechanism of actionit competes with acetylcholine (ach) molecules and binds to muscarinic acetylcholine receptors on the post-synaptic membrane of the motor endplate. it acts by combining with the cholinergic receptor sites in muscle and competitively blocking the transmitter action of acetylcholine. it blocks the action of ach and prevents activation of the muscle contraction process. it can also act on nicotinic presynaptic acetylcholine receptors which inhibits the release of ach.