Methantheline

A - Alimentary tract and metabolism

QA - Alimentary tract and metabolism

Methantheline is a synthetic quarternary ammonium antimuscarinic used to relieve cramps or spasms of the stomach, intestines, and bladder. It can be used together with antacids or other medicines, such as H2-receptor antagonists, in the treatment of peptic ulcer. Methantheline inhibits muscarinic actions at postganglionic parasympathetic neuroeffector sites.

Methantheline inhibits the muscarinic actions of acetylcholine on structures innervated by postganglionic cholinergic nerves as well as on smooth muscles that respond to acetylcholine but lack cholinergic innervation. These postganglionic receptor sites are present in the autonomic effector cells of the smooth muscle, cardiac muscle, sinoatrial and atrioventricular nodes, and exocrine glands. Depending on the dose, anticholinergics may reduce the motility and secretory activity of the gastrointestinal system, and the tone of the ureter and urinary bladder and may have a slight relaxant action on the bile ducts and gallbladder.

Drugs that bind to but do not activate MUSCARINIC RECEPTORS, thereby blocking the actions of endogenous ACETYLCHOLINE or exogenous agonists. Muscarinic antagonists have widespread effects including actions on the iris and ciliary muscle of the eye, the heart and blood vessels, secretions of the respiratory tract, GI system, and salivary glands, GI motility, urinary bladder tone, and the central nervous system.