Trospium chloride in the management of overactive bladder

Trospium chloride is an orally active, quaternary ammonium compound with antimuscarinic activity. It binds specifically and with high affinity to muscarinic receptors M(1), M(2) and M(3), but not nicotinic, cholinergic receptors. It is hydrophilic and does not cross the normal blood-brain barrier in significant amounts and, therefore, has minimal central anticholinergic activity. Peak plasma trospium chloride concentrations are attained approximately 5-6 hours after oral administration, which should occur before meals as concurrent food ingestion significantly reduces trospium bioavailability. Trospium chloride undergoes negligible metabolism by the hepatic Cytochrome P450 system; few metabolic drug interactions are known. While trospium chloride dosage adjustments based on age or sex appear unwarranted, such adjustments may be needed in patients with severe renal impairment. Direct comparative studies in patients with overactive bladder indicate that trospium chloride is at least as effective as oxybutynin and tolterodine. Placebo-controlled studies have also confirmed the efficacy of trospium chloride in terms of improved urodynamic parameters; small-scale, noncomparative studies have documented significant trospium chloride-induced improvements in patients with reflex neurogenic bladder, postoperative bladder irritation and radiation-induced cystitis; and observational studies including >10,000 patients have also revealed favourable findings for trospium chloride, including a marked decrease in incontinence episodes and substantial improvement in health-related quality of life. Trospium chloride is generally well tolerated, and significantly more so than immediate-release oxybutynin. The most frequent adverse events, occurring in >1% of trospium chloride-treated patients, are dry mouth, dyspepsia, constipation, abdominal pain and nausea. Available for many years in several countries outside North America, trospium chloride is likely to develop an important role in the management of overactive bladder following its approval in the US on 28 May 2004.