Nursing care
Anticholinergics: what to check before you give it
Written and reviewed by Dana Whitfield, RN, MSN · 5 min read · Updated September 2026
Short answer
Anticholinergics block acetylcholine at muscarinic receptors, drying secretions, relaxing smooth muscle, and slowing GI and urinary motility. The classic teaching triad is dry as a bone, red as a beet, blind as a bat. In an older adult the same mechanism often shows up first as acute confusion, not the textbook picture, so a new delirium in a patient on one of these drugs deserves a medication review before a dementia workup.
What it does and why it is prescribed
Anticholinergic drugs block muscarinic receptors, which stops acetylcholine from doing its usual job of stimulating smooth muscle, secretions, and parts of the CNS. That blockade is why atropine speeds up a bradycardic heart, why oxybutynin calms an overactive bladder, why scopolamine dries secretions before surgery, and why benztropine eases the tremor and rigidity of Parkinson's disease or drug-induced extrapyramidal symptoms.
The same receptor blockade explains the trouble. Acetylcholine is not selective to one organ, so a drug given for the bladder still reaches the eyes, the gut, the skin, and the brain. Every effect you see at the bedside, dry mouth, blurred near vision, constipation, flushed skin, traces back to this one mechanism, which is why the drug class is taught as a single pattern rather than drug by drug.
Nursing considerations before giving it
Check for narrow-angle glaucoma and significant prostatic hypertrophy before the first dose. Anticholinergics can precipitate an acute glaucoma crisis by dilating the pupil and raising intraocular pressure, and they can push a man with an enlarged prostate into urinary retention by relaxing bladder tone while the internal sphincter stays tight.
Baseline vital signs matter, particularly heart rate, because these drugs are vagolytic and will raise it. Review the rest of the medication list for other anticholinergic or sedating agents, antihistamines, tricyclic antidepressants, and some antipsychotics all add to the same burden, and that cumulative load is what tips an older adult into delirium.
In anyone over 65, weigh the drug against the Beers Criteria before it is given. Age-related decline in hepatic clearance and CNS reserve means a dose that is well tolerated in a younger adult can cause confusion in an older one at the same milligram amount.
What to monitor
Track heart rate and rhythm, urinary output, bowel pattern, and mental status at each shift. A rising heart rate, a bladder that is not emptying, or bowel sounds that are dropping off are all direct extensions of the drug's action and should be caught early rather than treated as unrelated complaints.
Mental status is the parameter to weight most heavily in an older adult. Anticholinergics cross the blood-brain barrier and block central muscarinic receptors, and the resulting confusion, agitation, or new disorientation can appear before, or instead of, the peripheral signs everyone is taught to expect. Document a baseline cognitive status before the first dose so a change is recognisable, and reassess after each dose increase.
Side effects versus adverse effects
Expected side effects follow the mnemonic dry as a bone, red as a beet, blind as a bat: dry mouth and dry skin, flushed face from vasodilation, and blurred near vision from pupil dilation and loss of accommodation. These are predictable extensions of the mechanism and usually manageable with sips of water, sunglasses, and reassurance.
Adverse effects are the same mechanism taken further. Urinary retention, severe constipation progressing toward ileus, tachycardia with palpitations, hyperthermia from an inability to sweat, and acute confusion or hallucinations in an older adult all cross from tolerable to reportable. The distinction is not a different drug reaction, it is the same pharmacology at an intensity that threatens safety.
What to hold for and when to call
Hold the dose and call the prescriber for a heart rate outside the parameters set for that patient, for absent bowel sounds or no bowel movement over the expected interval, for a distended bladder with minimal output, or for eye pain with visual change, which can signal acute angle-closure glaucoma.
Call immediately for new confusion, agitation, or hallucinations in a patient who was previously oriented, and for hyperthermia in a warm environment, since the drug blocks sweating along with everything else. In an older adult, a sudden change in mental status on one of these medications is treated as a medication effect until proven otherwise, not as a new diagnosis of dementia.
Patient teaching
Teach the patient to expect a dry mouth and to manage it with sugar-free gum or frequent sips of water rather than sweetened drinks, since the reduced saliva flow already raises the risk of dental caries. Warn about blurred near vision and advise caution with driving or reading fine print until the effect is known.
Cover heat safety specifically: because sweating is reduced, the patient should avoid strenuous activity in hot weather and recognise early signs of overheating. Advise increasing fluid and fibre intake to offset constipation, and tell the patient or family to report any new confusion, unusually fast heartbeat, or inability to pass urine straight away rather than waiting for the next appointment.
The next step on this is the same as on everything else here: answer questions and read the rationales. Our pharmacology practice questions are the closest set to what this page covers.
One question from the pharmacology set
A client with heart failure is started on furosemide 40 mg PO daily. Which findings should the nurse report to the provider before administering the next dose? Select all that apply.
Rationale
Furosemide is a loop diuretic, so the two things you are watching are potassium and kidney function. A potassium of 2.9 mEq/L is below the 3.5–5.0 reference range and puts the client at risk for dysrhythmia — hold and report. Muscle cramps with palpitations are the clinical face of that same hypokalemia, so they are reported together, not separately. A creatinine that doubles signals the diuresis has outrun renal perfusion. A blood pressure of 132/78 and a 1 kg loss are the expected response to the drug working, not reasons to hold it.
Answer: A, D, E
Common questions
Why do anticholinergics cause confusion in older adults instead of the usual dry mouth?
The drugs cross the blood-brain barrier and block central muscarinic receptors alongside the peripheral ones. Older adults have less cholinergic reserve and slower drug clearance, so the central effect can dominate and appear as delirium before or without the classic peripheral signs.
What is the mnemonic for anticholinergic side effects?
Dry as a bone, red as a beet, blind as a bat covers dry mucous membranes and skin, facial flushing from vasodilation, and blurred near vision from pupil dilation. Some versions add mad as a hatter for CNS effects and full as a flask for urinary retention.
Can anticholinergics be given to a patient with glaucoma?
They are contraindicated in narrow-angle glaucoma because pupil dilation can precipitate an acute pressure crisis. Open-angle glaucoma is generally lower risk, but the prescriber should confirm the specific type before the drug is started.
What should the nurse do if an older patient becomes confused after starting an anticholinergic?
Recheck vital signs, assess for urinary retention and constipation, and hold the next dose while notifying the prescriber. Treat the confusion as a probable medication effect first, since it often resolves once the drug is stopped or reduced.
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