A 52-year-old man with Parkinson's disease is started on benztropine 2 mg daily to manage his motor symptoms. Two weeks later, he presents to clinic complaining of difficulty initiating urination and a sensation of incomplete bladder emptying. Vital signs are stable (BP 136/84, HR 82, RR 14). Physical examination reveals a palpable suprapubic mass consistent with urinary retention. Post-void residual volume is 210 mL on bladder ultrasound. Urinalysis and renal function are normal. Which of the following best explains the urinary retention observed in this patient?
- A)Blockade of muscarinic M1 receptors in the cerebral cortex, reducing central processing of micturition
- B)Blockade of muscarinic M3 receptors on the detrusor muscle, impairing parasympathetic-mediated bladder contractionGABARITO
- C)Activation of nicotinic receptors in the parasympathetic ganglia, increasing acetylcholine sensitivity
- D)Inhibition of sympathetic β3-adrenergic receptors on the bladder dome, preventing urine storage
- E)Competitive antagonism of acetylcholine at the neuromuscular junction of the external urethral sphincter
Explicação
Benztropine is a tertiary amine anticholinergic that crosses the blood-brain barrier and blocks muscarinic receptors centrally and peripherally. At the bladder, M3 receptor blockade on the detrusor smooth muscle prevents acetylcholine-mediated contraction, whi... Ver explicação completa e trilha adaptativa →