Screen carefully for cardiopulmonary disease and anatomic obstruction before starting bethanechol; parasympathomimetic effects can rapidly destabilize vulnerable children.
Absolute contraindications include any mechanical obstruction of the GI or GU tract, situations with high vagal tone risk (severe bradyarrhythmias), and conditions where bronchoconstriction could be life-threatening. Relative contraindications focus on comorbidities that amplify cholinergic adverse effects or complicate monitoring, such as reactive airway disease, peptic ulcer disease, seizure disorders, or autonomic dysfunction.
Mechanical obstruction of the urinary or gastrointestinal tract, including bladder neck obstruction and intestinal blockage, because muscarinic stimulation can precipitate perforation or urinary retention crises; confirm patency before prescribing.
Reactive airway disease with active bronchospasm or a history of severe asthma attacks — increased vagal tone may trigger life-threatening bronchoconstriction and hypoxia.
Baseline bradycardia, hypotension, or conduction disease; cholinergic agonism can exaggerate vagal responses, so titrate slowly with cardiac monitoring when therapy is unavoidable.
Hyperthyroidism or peptic ulcer disease, where enhanced motility and acid secretion increase the risk of arrhythmias or GI bleeding; coordinate with endocrinology or gastroenterology.
Epilepsy or Parkinsonism, because central cholinergic effects may lower seizure threshold or worsen tremor; consider alternative bladder emptying strategies if symptoms destabilize.