A stable solid hydrate of a muscarinic receptor antagonist is useful in the treatment of irritable bowel syndrome, diverticular disease, oesophageal achalasia, chronic obstructive airways disease, over active bladder (including symptoms of incontinence, urge and frequency), urinary incontinence, neurogenic urinary urgency or pollakiuria, treatment of bladder functional disorder, urinary leakage, painful or difficult urination caused by neurogenic bladder, spastic or hypertonic bladder, dysfunctional bladder syndrome, gastrointestinal disorders including gastrointestinal hyperactivity, and relaxing effect on intestinal smooth muscle cells.