Mean absolute bioavailability of a 20 mg dose is 9.6% (range: 4.0 to 16.1%). Peak plasma concentrations (Cmax) occur between 5 and 6 hours post-dose. Mean Cmax increases greater than dose-proportionally; a 3-fold and 4-fold increase in Cmax was observed for dose increases from 20 mg to 40 mg and from 20 mg to 60 mg, respectively. AUC exhibits dose linearity for single doses up to 60 mg. Trospium chloride exhibits diurnal variability in exposure with a decrease in Cmax and AUC of up to 59% and 33%, respectively, for evening relative to morning doses.Administration with a high fat meal resulted in reduced absorption, with AUC and Cmax values 70 to 80% lower than those obtained when trospium chloride was administered while fasting. Therefore, it is recommended that trospium chloride should be taken at least one hour prior to meals or on an empty stomach.Protein binding ranged from 50 to 85% when concentration levels of trospium chloride (0.5 to 50 ng/mL) were incubated with human serum in vitro. The 3H-trospium chloride ratio of plasma to whole blood was 1.6:1. This ratio indicates that the majority of 3H-trospium chloride is distributed in plasma. The apparent volume of distribution for a 20 mg oral dose is 395 (± 140) liters.The metabolic pathway of trospium in humans has not been fully defined. Of the 10% of the dose absorbed, metabolites account for approximately 40% of the excreted dose following oral administration.
Medical uses
Trospium chloride is used for the treatment of overactive bladder with symptoms of urge incontinence and frequent urination.It shouldnt be used with people who retain urine, who have severe digestive conditions, myasthenia gravis, narrow-angle glaucoma, or tachyarrhythmia.It should be used in caution with 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.Trospium chloride is rated Pregnancy Category C, as there are no adequate and well-controlled studies of trospium chloride in pregnant women and there were 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
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. Mechanism of action
Trospium chloride is a muscarinic antagonist. Trospium chloride blocks the effect of acetylcholine on muscarinic receptors organs that are responsive to the compounds, including the bladder. Its parasympatholytic action relaxes the smooth muscle in the bladder. Receptor assays showed that trospium chloride  has negligible affinity for nicotinic receptors as compared to muscarinic receptors at concentrations obtained from therapeutic doses. Pharmacokinetics
After oral administration, less than 10% of the dose is absorbed.