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.

Hyoscyamine methylbromide, a muscarinic acetylcholine receptor antagonist, was studied as an antispasmodic.

Pipenzolate bromide (JB-323), an anticholinergic agent, which binds to muscarinic acetylcholine receptors as an antagonist. Pipenzolate bromide was studied as an antispasmodic agent, and to treat peptic ulcer.

Homatropine (used in a form of bromide or methylbromide salts) is an analogue of atropine, which acts as an antagonist of muscarinic receptors. Homatropine was approved for the treatment of cough in combination with hydrocodone bitartrate.

Methylatropine (methylatroponium) is a belladonna derivative. In 1902 the Bayer Company introduced atropine methonitrate, a quaternary ammonium salt of atropine (Eumydrin), as a mydriatic for dilation of the pupil during ophthalmic examination. Due to its highly polar nature it penetrates less readily into the central nervous system than atropine and was therefore introduced for relieving pyloric spasms in infants. Atropine methyl nitrate is a muscarinic acetylcholine receptor antagonist that does not cross the blood-brain barrier. Atropine methyl nitrate has been used for its peripheral muscarinic effects (targeting the bladder, respiratory tract, and to block parasympathetic signaling to the heart, among others) and to separate central from peripheral nervous system effects, or to protect against peripheral side effects when using muscarinics that do cross the blood brain barrier.

Mandelic acid is an aromatic alpha hydroxy acid that is used for the treatment of urinary tract infections. The drug is marketed in Canada under the name Mandelamine (as a complex with methenamine). Mandelic acid exerts its antibacterial effect mainly by increasing urine acidity. Moreover, mandelic acid is used as a serum for the treatment of wrinkles.

Methylnaltrexone, is a peripherally acting μ-opioid receptor antagonist that acts on the gastrointestinal tract to inhibit the opioid-induced decrease in gastric motility and transit time. It is used to treat opiate-induced constipation in adults with chronic non-cancer pain and in adults with advanced illness who are receiving palliative care.