Anticholinergics (Atropine)

Sialorrhea. "Anticholinergic drugs such as atropine, hyoscine, glycopyrrolate, and amitryptiline have been found to be beneficial in the management of sialorrhea. Salivary gland irradiation and botulinum toxin injections have also been proposed as treatment modalities." "Anticholinergic drugs have been associated with urinary retention and constipation." "They are contraindicated in patients with heart block and benign prostatic hypertrophy."

This class appears twice in this disorder, on opposite sides. As a cause: atropine, oxybutynin, scopolamine, hyoscyamine, propantheline and dicyclomine block the muscarinic receptors the detrusor needs in order to contract, and they sit at the top of the drug list that tips a man with BPH into acute retention — as do antihistamines with anticholinergic effects. As a cautious treatment: antimuscarinics are "commonly used for urinary frequency, urgency, and bladder overactivity symptoms… also useful for the symptomatic management of detrusor instability due to bladder outlet obstruction from BPH." The safety rule is the whole teaching point: bladder-relaxing therapy "may be used alone if there is good urinary flow and low PVRs," but is "often used together with alpha-blockers for most patients with symptomatic BPH … to reduce postvoid volumes, provide symptom relief, and minimize the risk of urinary retention." Practically — never give an anticholinergic alone to a man with a high post-void residual or a poor stream.

The other half of dual bronchodilation: LAMAs (tiotropium, umeclidinium, aclidinium, glycopyrronium) provide 24-hour maintenance bronchodilation as the LAMA in LABA + LAMA. In an acute exacerbation, the SAMA ipratropium is nebulized with the SABA — every 20 minutes initially, then every 4–6 hours — the standard inpatient combination.

On this page as a precipitant, and the scope of the warning is as important as the warning itself. "Over 60 drugs have been reported to be associated with AAC and are considered risk factors, particularly for individuals with OCULAR PREDISPOSITIONS. These drugs include topical anticholinergic pupil dilators, such as ATROPINE and CYCLOPENTOLATE, and systemic medication, including TOPIRAMATE, SULFONAMIDES, DULOXETINE, and PHENOTHIAZINES." The mechanism is already on the page: mydriasis increases iris-lens apposition and can tip a narrow angle into pupillary block. The scope limit is what makes this teachable rather than ignorable. The sourced risk is specifically about angle-closure-predisposed eyes, and no fetched source states a contraindication in open-angle glaucoma — which is 74% to 80% of all glaucoma. So the rule is: ask about a known narrow angle or a prior angle-closure attack before any pupil-dilating or anticholinergic drug, and say which type of glaucoma the caution applies to every single time. The undifferentiated warning — "avoid anticholinergics in glaucoma" — is both wrong and, because it is wrong, routinely ignored. The follow-up instruction is sourced too: "patients taking these medications should undergo regular ophthalmic examinations, particularly if they have [angle-closure] risk factors." The class page owns the anticholinergic pharmacology.

The other side of the imbalance: with dopamine gone, striatal acetylcholine is relatively unopposed, and benztropine or trihexyphenidyl restore the balance by blocking muscarinic receptors. Their niche is tremor — benztropine is an adjunct for all forms of parkinsonism and is particularly useful for tremor, and they (with amantadine) treat drug-induced parkinsonism once the offending drug is stopped. The limits matter more than the indication: they "can lead to adverse effects such as confusion and hallucinations," and both agents are Beers-criteria potentially inappropriate in older adults (confusion, hallucinations, delirium, falls, urinary retention). Teach heat intolerance — they block sweating — and, like the dopaminergic drugs, they are not stopped abruptly.

A narrow, two-condition role — and the boundaries matter more than the indications. Anticholinergics treat acute dystonia and antipsychotic-induced parkinsonism. For an acute dystonic reaction, an intramuscular injection of 1 to 2 mg of benztropine provides rapid relief, with further injections if needed, and parenteral diphenhydramine or benztropine resolves the symptoms dramatically within 10 to 30 minutes — a clock the nurse should be watching. For parkinsonism, management is dose reduction, changing agents, or amantadine or an anticholinergic such as benztropine. Three sourced boundaries are as examinable as the indications. First, anticholinergics are not recommended for tardive dyskinesia, akathisia, or neuroleptic malignant syndrome. Second, in tardive dyskinesia they should be discontinued, because they may worsen it. Third, akathisia "does not generally respond to anticholinergic agents" — which is itself evidence that akathisia has a different mechanism. Prophylaxis is not routine: current guidelines generally do not recommend prophylactic or long-term anticholinergics in patients on antipsychotics, because the peripheral burden (dry mouth, urinary disturbance, constipation) and the central harm (cognitive dysfunction and delirium) land on a population already cognitively impaired, and may worsen that impairment and quality of life. The single sourced exception is narrow: benztropine may be used for the first week of a new antipsychotic and then tapered slowly to prevent an acute dystonic reaction. Remember also that the antipsychotic itself has anticholinergic effects — urinary retention, blurred vision, tachycardia, constipation and cognitive difficulty, especially in older patients — so the two burdens compound, and decreasing the antipsychotic dose is the first-choice strategy for those symptoms.

[Urge] Antimuscarinics (oxybutynin). Oxybutynin is "a muscarinic antagonist indicated for the treatment of overactive bladder with symptoms of urge urinary incontinence, urgency, and frequency." They "block the action of acetylcholine and provide an antispasmodic effect on smooth muscle"; they "do not directly affect sphincteric competence." Contraindicated "in patients with urinary retention, gastric retention and other severe decreased gastrointestinal motility conditions, uncontrolled narrow-angle glaucoma" — never for overflow. Effects: "dry mouth, constipation, dizziness, and drowsiness, which can increase fall risk in older adults"; blurred vision; "Heat prostration due to decreased sweating"; alcohol "may enhance the drowsiness." ER tablets: "should not chew, divide, or crush"; take "at approximately the same time each day."

Turn UP “rest-and-digest.” Used for urinary retention, myasthenia, dry mouth and the eye; methacholine tests airway reactivity and physostigmine reverses anticholinergic poisoning. Overdose = cholinergic crisis (SLUDGE).

Release the sympathetic α squeeze. Nonselective phentolamine and phenoxybenzamine control pheochromocytoma; uroselective tamsulosin, alfuzosin and silodosin ease BPH. Metyrosine cuts catecholamine synthesis instead. Watch for orthostatic hypotension.