New confusion, agitation, or hallucinations, especially in an older adult — hold further doses and notify the provider.
Before you read
Test yourself first: 5 questions
Question 1 of 5
A client receiving an antipsychotic suddenly develops a stiff, twisted neck and the eyes deviate upward. Which medication does the nurse anticipate administering?
Answer: A. These findings describe acute dystonia (torticollis and oculogyric crisis), an early extrapyramidal reaction. The first-line treatment is an anticholinergic such as benztropine or the antihistamine diphenhydramine, given IM or IV for rapid relief. Propranolol is used for akathisia, lithium is a mood stabilizer, and lorazepam alone does not reverse a dystonic reaction.
Question 2 of 5
A client experiences an acute dystonic reaction with torticollis and oculogyric crisis shortly after receiving an antipsychotic. Which medication does the nurse anticipate administering?
Answer: B. Acute dystonia is an early extrapyramidal reaction (muscle spasms of the neck, eyes, and back). It is treated with an anticholinergic such as benztropine or the antihistamine diphenhydramine, which counteract the dopamine-acetylcholine imbalance.
Question 3 of 5
A client receiving haloperidol develops a sudden, painful spasm with the neck twisting to one side and the eyes deviating upward. Which intervention should the nurse anticipate?
Answer: A. This describes acute dystonia (torticollis and oculogyric crisis), an early extrapyramidal reaction. The treatment is an anticholinergic such as IM/IV benztropine or diphenhydramine, which rapidly relieves the spasm. It is uncomfortable but treatable; prompt administration is the expected intervention.
Question 4 of 5
A provider orders an IM injection of a medication for acute agitation that does not respond to verbal de-escalation. Which combination is a commonly used agent for chemical de-escalation?
Answer: A. Haloperidol combined with lorazepam (often with diphenhydramine to prevent dystonia) is a recognized regimen for acute agitation. The benzodiazepine sedates and the antipsychotic targets psychosis-driven agitation.
Question 5 of 5
Using Beers criteria principles, which medication is generally considered potentially inappropriate for an older adult because of its anticholinergic and sedating effects?
Answer: B. Diphenhydramine, a first-generation antihistamine, is flagged on the Beers criteria because its strong anticholinergic effects cause confusion, urinary retention, constipation, and falls in older adults. Acetaminophen, lisinopril, and metformin are not on that high-risk anticholinergic list.
Keep the streak going with more questions like these, each with a full rationale.
What is diphenhydramine?
It blocks H1 receptors and, because it crosses the blood-brain barrier, causes marked sedation. It also blocks muscarinic receptors, producing strong anticholinergic effects. That combination makes it risky for older adults, who face confusion, urinary retention, and falls. The nurse prevents falls, watches for anticholinergic effects, and avoids stacking it with other sedatives or anticholinergic drugs.
Key points to remember
- It blocks H1 receptors (acting as an inverse agonist), crosses into the brain to cause drowsiness, and blocks muscarinic receptors to cause anticholinergic effects.
- Anticholinergic effects: dry mouth, urinary retention, constipation, blurred vision, and tachycardia.
- In anaphylaxis it is an adjunct only. Epinephrine comes first, and an antihistamine must never delay it.
- Adult dose 25–50 mg PO, IM, or IV every 4–6 hours as needed; oral maximum 300 mg/day. Give IV no faster than 25 mg/min.
- Older adults: the Beers Criteria advise avoiding it because of strong anticholinergic effects, confusion, and fall risk.
- Children may react with paradoxical excitation (agitation and confusion) instead of sedation.
- Contraindicated in neonates, premature infants, and breastfeeding mothers. Use caution with glaucoma or raised eye pressure, urinary retention or BPH, asthma, heart disease, and hypertension.
Signs & symptoms
- Drowsiness, dry mouth, constipation
- Urinary retention, blurred vision
Nursing priorities
- Put fall precautions in place, especially for older adults, because sedation and dizziness cause falls.
- Assess urine output, bladder distention, and bowel function, because anticholinergic effects cause retention and constipation.
- Review the medication list for alcohol, sedatives, and other anticholinergics (tricyclic antidepressants, benztropine, oxybutynin, hydroxyzine), because their effects add up.
- In anaphylaxis, give epinephrine first and diphenhydramine only afterward as ordered, because an antihistamine must not delay first-line treatment.
- Push IV doses no faster than 25 mg/min, because that is the maximum recommended rate.
- Teach no driving until the effect is known, because CNS depression impairs driving.
Worked example
- Cue: An older adult given diphenhydramine at bedtime for sleep is found overnight confused, trying to climb out of bed, with a distended bladder.
- Meaning: Anticholinergic delirium and urinary retention, the reason the Beers Criteria list this drug.
- Action: Keep the client safe (bed low, stay nearby), assess the bladder, notify the provider, and hold further doses.
- Evaluation: Confusion clears, the client voids, and the order is changed to a non-anticholinergic option.
Patient teaching
- This medicine makes most people sleepy. Don't drive until you know how it affects you.
- Don't drink alcohol or take other sleep aids or sedating medicines with it.
- For dry mouth, try sugarless gum. Drink fluids and eat fiber to prevent constipation, and call if you can't pass urine.
- Read the label, don't take more than recommended, and store it where children can't reach it.
Memory tricks
- Anticholinergic effects: 'can't see, can't pee, can't spit, can't poop.'
Common mistakes
- Giving diphenhydramine before epinephrine in anaphylaxis.
- Choosing it as a sleep aid for an older adult. It is on the Beers list, and sleep-medicine guidance advises against it for insomnia.
- Expecting every child to get sleepy. Children can become agitated instead.
- Giving it for motion sickness after symptoms start. It is used for prevention, not for existing motion sickness.
Red flags: report now
- New confusion, agitation, or hallucinations, especially in an older adult — hold further doses and notify the provider.
- No urine output with a distended bladder — notify the provider; likely anticholinergic urinary retention.
- Overdose with agitation, seizures, arrhythmias, or a widened QRS — call the rapid response team and poison control; sodium bicarbonate treats QRS widening and benzodiazepines treat seizures.
- Agitation or confusion in a child after a dose — paradoxical reaction: stop the drug and report it.
References
Clinical references for this topic
