Methoctramine is a highly selective antagonist for cardiac M2 muscarinic receptors, which are involved in reducing heart rate after stimulatory actions of the parasympathetic nervous system. At nanomolar concentrations, methoctramine has been shown to strongly inhibit bradychardia induced by both vagal stimulation and acetylcholine.Methoctramine has low affinity for M1 receptors and non-cardiac M2 receptors.
