Overactive bladder (OAB) is characterized by urgency, with or without urge incontinence, and is usually accompanied by an increased micturition frequency and nocturia in the absence of other identifiable metabolic or pathologic conditions affecting the lower urinary tract. Although OAB is a common, distressing condition, a large number of patients remain untreated. The antimuscarinic drug medication, in conjugation with behavioral therapy such as bladder training, remains the first-line management of patients with OAB. Drugs used to treat OAB affect the nerve and function of the detrusor muscle, causing the detrusor muscle to relax and thus reduce the frequency and intensity of contractions of the bladder. These drugs work by blocking the binding of neurotransmitters called acetylcholine to specific sites of the bladder muscle. The binding of neurotransmitters to the receptor sites causes a sequence of changes that result in muscle contractions. Blocking this binding prevents the contraction of the bladder. Adverse events, such as dry mouth, dry eyes, constipation and headache can occur in all antimuscarinic drugs. In addition, intravesical injection can be used for patients who do not respond to oral medication.