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Pharmacology ` PHARMACOLOGY—AUTONOMIC dRUGS Pharmacology ` PHARMACOLOGY—AUTONOMIC dRUGS SEcTIoN II 237
Micturition control Micturition center in pons regulates involuntary M₃-receptor
bladder function via coordination of Detrusor muscle
sympathetic and parasympathetic nervous Pelvic nerve β₃-receptor
systems. (parasympathetic α₁-receptor
input)
⊕ sympathetic urinary retention
Hypogastric nerve
⊕ parasympathetic urine voiding. Some (sympathetic input) Internal urethral
sphincter
autonomic drugs act on smooth muscle External urethral
receptors to treat bladder dysfunction. Pudendal nerve sphincter
(somatic input) Nicotinic receptor
dRUGS MECHANISM USE
Muscarinic ⊝ M 3 receptor relaxation of detrusor smooth Urgency incontinence
antagonists muscle detrusor overactivity
(eg, oxybutynin)
Muscarinic ⊕ M 3 receptor contraction of detrusor Urinary retention
agonists smooth muscle bladder emptying
(eg, bethanechol)
Sympathomimetics ⊕ β 3 receptor relaxation of detrusor smooth Urgency incontinence
(eg, mirabegron) muscle bladder capacity
α 1 -blockers ⊝ α 1 -receptor relaxation of smooth BPH
(eg, tamsulosin) muscle (bladder neck, prostate) urinary
obstruction
FAS1_2019_05-Pharmacology.indd 237 11/7/19 4:08 PM
