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.