Atropine inhibits the muscarinic actions of acetylcholine on structures innervated by postganglionic cholinergic nerves, and on smooth muscles which respond to endogenous acetylcholine but are not so innervated. As with other antimuscarinic agents, the major action of atropine is a competitive or surmountable antagonism which can be overcome by increasing the concentration of acetylcholine at receptor sites of the effector organ (e.g., by using anticholinesterase agents which inhibit the enzymatic destruction of acetylcholine). The receptors antagonized by atropine are the peripheral structures that are stimulated or inhibited by muscarine (i.e., exocrine glands and smooth and cardiac muscle). Responses to postganglionic cholinergic nerve stimulation also may be inhibited by atropine but this occurs less readily than with responses to injected (exogenous) choline esters. Atropine is relatively selective for muscarinic receptors. Its potency at nicotinic receptors is much lower, and actions at non-muscarinic receptors are generally undetectable clinically. Atropine does not distinguish among the M1, M2, and M3 subgroups of muscarinic receptors.

Atropine-N-oxide hydrochloride is an alkaloid of the belladonna plants. It is the major metabolite of atropine. It is a competitive nonselective antagonist at central and peripheral muscarinic acetylcholine receptors.

Tropic acid (Tropate) is a chiral substance, existing as either a racemic mixture or as a single enantiomer. Tropate is classified as a beta hydroxy acid or a Beta hydroxy acid derivative. Beta hydroxy acids are compounds containing a carboxylic acid substituted with a hydroxyl group on the C3 carbon atom. Tropate is considered to be soluble (in water) and acidic. Tropate can be synthesized from hydratropic acid and propionic acid. Tropate can be synthesized into tropan-3alpha-yl 3-hydroxy-2-phenylpropanoate. Tropic acid is proposed be used topicaly for the treatment of wrinkles.

Hyoscyamine as a natural plant alkaloid derivative and anticholinergic. Hyoscyamine is used to treat a variety of stomach/intestinal problems such as cramps and irritable bowel syndrome. It is also used to treat other conditions such as bladder and bowel control problems, cramping pain caused by kidney stones and gallstones, and Parkinson's disease. In addition, it is used to decrease side effects of certain medications (drugs used to treat myasthenia gravis) and insecticides. Hyoscyamine inhibits specifically the actions of acetylcholine on structures innervated by postganglionic cholinergic nerves and on smooth muscles that respond to acetylcholine but lack cholinergic innervation. These peripheral cholinergic receptors are present in the autonomic effector cells of the smooth muscle, cardiac muscle, the sinoatrial node, the atrioventricular node, and the exocrine glands. At therapeutic doses, it is completely devoid of any action on autonomic ganglia. Side effects include dry mouth and throat, increased appetite leading to weight gain, eye pain, blurred vision, restlessness, dizziness, arrhythmia, flushing, and faintness. Additive adverse effects resulting from cholinergic blockade may occur when hyoscyamine is administered concomitantly with other antimuscarinics, amantadine, haloperidol, phenothiazines, monoamine oxidase (MAO) inhibitors, tricyclic antidepressants or some antihistamines.