Detrusor muscle contraction causes micturition. When detrusor relaxes and the sphincters close urine is stored. Whereas voiding requires contraction of detrusor -accompanied by relaxation of sphincters. Since detrusor contracts under parasympathetic influence, anticholinergic (specifically antimuscarinic) drugs are used to treat overactive bladder disease or detrusor instability. Overactive urinary bladder can be successfully treated with muscarinic receptor antagonists. These agents can lower intravesical pressure, increase capacity, and reduce the frequency of contractions by antagonizing parasympathetic control of the bladder; they also may alter bladder sensation during filling. Solifenacin is relatively selective for muscarinic receptors of the M3 subtype, giving it a orable efficacy. Oxybutynin, Tolterodine are commonly used drugs competitively bind to cholinergic receptors. These medications appear to work at the level of the detrusor muscle by competitively inhibiting acetylcholine at muscarinic receptors (M2 and M3). These agents thereby blunt detrusor contractions to reduce the number of incontinence episodes and volume lost with each. These medications are significantly better than placebo at improving symptoms of urge urinary incontinence and overactive bladder. Duloxetine is a selective serotonin and norepinephrine reuptake inhibitor. It is approved for the treatment of major depression, generalized anxiety disorder, and diabetic peripheral neuropathic pain in adults. It is not used for detrusor instability. Ref: Brown J.H., Laiken N. (2011). Chapter 9. Muscarinic Receptor Agonists and Antagonists. In L.L. Brunton, B.A. Chabner, B.C. Knollmann (Eds), Goodman & Gilman's The Pharmacological Basis of Therapeutics, 12e