Forgetfulness, confusion and difficulty concentrating can sometimes be medication side effects, particularly in older adults, people taking high doses and patients using several drugs that affect the brain.
A Health review updated June 29 identifies seven broad groups associated with memory or attention problems: benzodiazepines, anti-seizure medicines, opioids, tricyclic antidepressants, antihistamines, sleeping pills and anticholinergic medicines for overactive bladder. The degree of risk varies widely by the drug, dose, duration and patient.
Benzodiazepines such as lorazepam, alprazolam and diazepam slow activity in the central nervous system and can interfere with forming new memories. The effect may be temporary, but older adults clear the drugs more slowly and can also face greater risks of sedation, falls and delirium. These medicines should not be stopped abruptly because withdrawal can be dangerous.
Anti-seizure drugs reduce excessive electrical activity in the brain, but drowsiness and slowed thinking can make it harder to pay attention and store new information. Opioids can also impair alertness and memory, especially at higher doses or when combined with alcohol, sedatives or other medicines that depress the nervous system.
Tricyclic antidepressants and many bladder-control medicines have anticholinergic effects, meaning they block acetylcholine, a chemical messenger important for attention and learning. First-generation antihistamines such as diphenhydramine also enter the brain readily and can cause drowsiness or confusion. Newer allergy medicines generally cause less sedation, although patients should still check the label and ask a pharmacist.
Prescription sleep medicines including zolpidem, eszopiclone and zaleplon can cause next-day impairment, unusual behavior or gaps in memory. Sleep deprivation itself also damages attention, which can make it difficult to determine whether the underlying sleep problem, the medicine or both are responsible.
An association between long-term medicine use and dementia does not prove a drug caused the disease. People who take these treatments may have conditions that independently affect cognition, and observational studies cannot remove every source of bias. Still, cumulative exposure to strong anticholinergic drugs is an important reason for regular medication review.
Anyone who notices a change after starting or increasing a medicine should document when symptoms began and contact the prescriber or pharmacist. A clinician may adjust the dose, change the timing, treat another cause or choose an alternative. Patients should also include over-the-counter sleep aids and allergy products in the review because they are easy to overlook.
Sudden confusion, trouble speaking, one-sided weakness, severe headache or loss of consciousness can signal an emergency rather than a routine side effect and requires immediate care.
Source: Health, updated June 29, 2026. Additional verification: peer-reviewed research and medication-safety references cited by Health.
