Overactive bladder syndrome is defined as "Urgency, with or without urge incontinence, usually with frequency and nocturia." (Abrams 2002). This is a prevalent condition. In a survey done in Europe (France, Germany, Italy, Spain, Sweden, and the United Kingdom), of the 16 776 subjects interviewed 16.6% had overactive bladder, giving the estimated prevalence of 22.18 million individuals affected. Interestingly, urge incontinence was reported by only 36% of respondents (Milsom 2001). In a similar study, in the United States, the National Overactive Bladder Evaluation (NOBLE) program, an estimated prevalence of 33 million Americans were affected by overactive bladder. Of these, 12 million (37%) were incontinent (Stewart 2001). Therefore overactive bladder (OAB) syndrome could in fact be divided into 'OAB wet' or 'OAB dry' ie with or without urge urinary incontinence respectively. It is however important to note that urinary incontinence is not a necessary prerequisite for diagnosis as defined by the International Continence Society (Steers 2002).

The prevalence of OAB in the population of 40 years and above are 15.6% and 17.4% in men and women respectively. There is an increasing prevalence of OAB with advancing age and both genders equally affected. The symtoms of urgency and or frequency are comparably prevalent irrespective of gender but urge incontinence is more prevalent in women (Milsom 2001).

OAB syndrome has economic and quality of life implications. It has been estimated that the economic cost of OAB was US$12.02 billion in 2000 in the United States (Hu 2003). It is also associated with poorer quality of life indices as shown by the Short Form (SF) 36 questionnaire, King's Health Questionnaire and also found to have a higher depression scores and a poorer quality of sleep (Stewart 2001;Stewart 2003 Kelleher 1997).

The pathophysiology of the overactive bladder remains to be fully elucidated. However, the involvement of the autonomic nervous system in bladder/detrusor function is recognised (de Groat 1997). The motor nerve supply to the bladder is via the parasympathetic nervous system (via sacral nerves S2,3,4) (Ouslander 1986; Ouslander 1982; Abrams 1988) which effects detrusor muscle contraction. This is mediated by acetylcholine acting on muscarinic (M) receptors at the level of the bladder. (The bladder contains both M2 and M3 muscarinic receptor subtypes. Although the M2 subtype is more abundant, it is the M3 subtype which is mainly responsible for bladder contraction).(Andersson 2002). The rationale for using anticholinergic drugs in the treatment of overactive bladder syndrome is to block the parasympathetic acetylcholine pathway and thus abolish or reduce the intensity of detrusor muscle contraction. For the purpose of this review, the term 'anticholinergic' will refer to both anticholinergic and antimuscarinic drugs. The above however is an oversimplistic view of the pathophysiology of OAB: Purinergic receptors (P2X) has been identified in the human bladder and is associated with the OAB (O'Reilly 2001;O'Reilly 2002); morphologic changes in the detrusor muscle ultrastructure; evidence of patchy denervation of the bladder and enlarged sensory neurons; associated with medical conditions like irritable bowel syndrome, depression, anxiety and attention deficit hyperactivity disorder (Steers 2002).

Pharmacotherapy is one of the main treatment options in the management of overactive bladder syndrome.People suffering from urge incontinence from overactive bladder syndrome represent a significant proportion of the incontinent population (Kobelt 1997). The number of anticholinergic drugs available on the market is increasing and effectiveness has been assessed in both observational and randomised controlled trials (Thuroff 1991; Van Kerrebroeck 1998). However, uncertainty still exists as to whether anticholinergic drugs are effective, and if so, which ones, and by which route of administration. There are also questions about the role of anticholinergic drugs in differing patient groups (eg the elderly, male and female). Despite these uncertainties anticholinergics are increasingly being used in primary and secondary care settings particularly for the treatment of urge incontinence, and this has considerable resource implications (Kobelt 1997).

There are many studies of the effects of anticholinergic drugs but there is a need for a systematic, periodically updated, review of properly controlled studies to summarise the data. Four Cochrane reviews will consider them (one published review, Hay‐Smith 2002; two others are at the protocol stage, Ellis 2002; Patrick 2004; and the current review). This review compares anticholinergic drugs with other types or classes of drugs.