Medications That Can Cause Confusion or Delirium After Surgery
Delirium is a sudden change in mental status characterized by confusion, disorientation, and difficulty concentrating. It is one of the most common complications after surgery, affecting 10 to 50% of older adults in post-surgical care. Several classes of medications significantly increase delirium risk by affecting brain chemistry. Recognizing which medications carry this risk, identifying early warning signs, and knowing when to alert your care team can prevent delirium from becoming serious or prolonged.
Medications Most Likely to Cause Confusion
Anticholinergic medications block a brain neurotransmitter called acetylcholine, which is essential for memory, attention, and clear thinking. Common examples include diphenhydramine (Benadryl), certain bladder medications such as oxybutynin, some older antidepressants, and some antihistamines.
Opioid pain medications such as morphine, oxycodone, and hydrocodone can cause sedation, disorientation, and confusion, particularly in older adults or those with kidney or liver impairment that slows drug clearance.
Benzodiazepines such as lorazepam (Ativan), diazepam (Valium), and alprazolam (Xanax) are commonly used for anxiety or sleep but are a leading cause of medication-induced delirium in hospitalized patients.
Sleep aids including zolpidem (Ambien) and similar non-benzodiazepine sleep medications alter brain chemistry in ways that can cause next-day confusion or, less commonly, acute delirium at night.
Steroids at high doses can occasionally cause what is called steroid psychosis, a condition in which patients experience agitation, mood changes, confusion, or hallucinations.
Multiple medications together: the risk of confusion increases substantially when several of the above medication types are combined. This is called polypharmacy-associated delirium and is a particular concern after complex surgery.
Recognizing Delirium: Warning Signs
Delirium typically develops quickly, over hours to a day or two, rather than gradually over weeks like dementia.
Early signs include difficulty following conversations, short attention span, repeating questions, and appearing more drowsy or restless than expected.
A person with delirium may not know where they are, may confuse night and day, or may become suspicious, fearful, or agitated without clear reason.
Sundowning refers to a pattern of confusion that worsens in the late afternoon and evening. This is common in hospital-related delirium.
Hypoactive delirium (quiet confusion) can be mistaken for depression or fatigue. The person may be unusually still, slow to respond, or hard to rouse. This form is often missed but is just as important to report.
Prevention and What to Do
Before surgery, provide your care team with a complete list of all medications, including over-the-counter antihistamines and sleep aids. Medications can be adjusted or avoided based on delirium risk.
Staying oriented helps reduce delirium risk: keep a visible clock and calendar, maintain regular sleep and wake times, open curtains during the day, and limit excessive napping.
If the patient wears glasses or hearing aids, ensure they are available and in use. Sensory deprivation contributes to confusion.
Limit caffeine and alcohol during recovery, as these can disrupt sleep architecture and lower the threshold for confusion.
If new confusion appears, contact your care team promptly. Do not give additional medications without guidance. Removing or reducing the offending medication is often the most effective treatment.
For mild confusion, a calm environment, familiar faces, reassurance, and adequate hydration often help. Restraints and sedating medications are generally avoided unless safety is at immediate risk.
No. Delirium is a temporary, reversible state of confusion that comes on quickly and is caused by an identifiable trigger such as medication, infection, or sleep deprivation. Dementia is a progressive, long-term decline in cognitive function. However, people with existing dementia are more vulnerable to delirium. If a person with dementia suddenly becomes much more confused than their baseline, this change should be evaluated for a treatable cause like medication or infection.
Can Benadryl cause confusion after surgery?
Yes. Diphenhydramine (Benadryl) is one of the most common causes of medication-related delirium in older adults because of its strong anticholinergic activity. It is often found in over-the-counter sleep aids and combination cold medications. It should generally be avoided in adults over 65 during recovery unless specifically prescribed for a reason no safer alternative covers.
How long does delirium last?
Delirium typically resolves within a few days to a week once the underlying cause is identified and addressed. In some cases, particularly in older adults or those who were already cognitively vulnerable, it can persist longer. Full cognitive recovery may take weeks to months. Prompt identification and cause removal are the most important factors in shortening duration.
What should I tell the care team if I notice confusion in a family member?
Describe what is different from the person's normal baseline: when it started, whether it comes and goes, and any recent medication changes, missed doses, sleep disruptions, or signs of infection like fever or new pain. Families who know the patient's normal mental state are essential in helping the care team identify delirium early.
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This guide provides general information. For instructions tailored to your specific procedure, ask your provider about QR Rx care plans.
These medication guides are for educational purposes only and do not replace medical advice. Always follow your healthcare provider's specific medication instructions.
