Trospium chloride is a muscarinic antagonist used to treat overactive bladder. It has side effects typical of this class of drugs, namely dry mouth, stomach upset, and constipation; these side effects cause problems with people taking their medicine as directed. However it doesn't cause central nervous system side effects like some other muscarinic antagonists.

Chemically it is a quaternary ammonium cation which causes it to stay in periphery rather than crossing the blood–brain barrier. It works by causing the smooth muscle in the bladder to relax.

It was patented in 1966 and approved for medical use in 1974. It was first approved in the US in 2004, and an extended release version was brought to market in 2007. It became generic in the EU in 2009, and the first extended-release generic was approved in the US in 2012.

Trospium chloride is used for the treatment of overactive bladder with symptoms of urge incontinence and frequent urination.

It should not be used with people who retain urine, who have severe digestive conditions, myasthenia gravis, narrow-angle glaucoma, or tachyarrhythmia.

It should be used with caution in people who have problems with their autonomous nervous system (dysautonomia) or who have gastroesophageal reflux disease, or in whom fast heart rates are undesirable, such as people with hyperthyroidism, coronary artery disease and congestive heart failure.

There are no adequate and well-controlled studies of trospium chloride in pregnant women and there are signs of harm to the fetus in animal studies. The drug was excreted somewhat in the milk of nursing mothers. The drug was studied in children.

Side effects are typical of gastrointestinal effects of anticholinergic drugs, and include dry mouth, indigestion, and constipation. These side effects lead to problems with adherence, especially for older people. The only CNS side effect is headache, which was very rare. Tachycardia is a rare side effect.