Publisher Summary Cholinomimetics or cholinergic drugs are those drugs that cause effects similar to those resulting from introduction of acetylcholine, or simulation of ganglions of the parasympathetic nervous system. These drugs imitate action of endogenously released acetylcholine. Acetylcholine is the primary neurotransmitter in the parasympathetic division of the autonomic nervous system, which mainly innervates the gastrointestinal tract, eyes, heart, respiratory tract, and secretory glands. Cholinomimetics can be classified as: Direct-acting (receptor agonists), acting on muscarinic and nicotinic, and Indirect-acting (cholinesterase inhibitors), which, in turn, can be reversible or irreversible. Direct-acting cholinomimetics are drugs that act directly by stimulating cholinergic receptors. These drugs are divided into drugs that stimulate muscarinic (M-cholinoreceptors) or nicotinic (N-cholinoreceptors) receptors. Indirect-acting cholinomimetic drugs, such as anticholinesterase drugs are inhibitors of acetylcholine metabolism and have similar effects to direct-acting cholinomimetics. Finally, this chapter discusses the classification of cholinomimetics.