Side effects of drugs in elderly can be mistaken for dementia

The side effects of many drugs widely used by elderly people can be mistaken for dementia, leading to even more drugs being prescribed, warn doctors in a new report.

Among the most common of these effects are known as "anticholinergic" effects, named for their effects on the nervous system.

Among these are anticholinergic side effects, named for their effects on the nervous system. Besides dementia-like symptoms of confusion, memory loss and disorientation, potential side effects included glaucoma-like blurred vision, dry mouth, constipation, urinary problems, dizziness, likelihood of falling, anxiety, rapid shallow breathing, and irregular or rapid heartbeat.

Many of the prescription drugs used in the treatment of Parkinson's disease, depression, allergies, migraine, and irritable bowel syndrome could cause these side effects.

"In the USA, people over 65 consume 30% of prescriptions and 40% of over-the-counter remedies, despite making up only 13% of the population," the study authors write. "In the UK, elderly people comprise only 18% of the population but use 45% of all prescription drugs, some of which are prescribed inappropriately and without proper attention to side effects," they note. "Failure to identify side effects can lead to use of other drugs to treat the symptoms, rather than adjustment of the dose of the drug responsible."

They add, "Some side effects can be mistaken for the effects of old age and age-related illness. This is particularly the case for anticholinergic side effects, which are among the most common drug-related effects experienced by elderly people living in nursing and residential homes."

In addition, the number of drugs with anticholinergic potential available without prescription is increasing, making it more difficult to monitor the situation. For example, histamine H2 antagonists such as

• cimetidine (Tagamet)
• famotidine (Pepcid)
• ranitidine (Zantac)

could be bought over-the-counter for indigestion.

Other over-the-counter drugs that could cause anticholinergic side effects included hay fever treatments, cold and flu medicines, sleeping pills and anti-diarrhoea treatments.

Since many elderly patients take several medications at once, this increases the likelihood of 'anticholinergic load.' The elderly were also more at risk because their metabolism was often less efficient.

The authors recommend that physicians "be alert to the possibility that dry mouth, constipation and blurred vision may be caused by medication. Changes in intellectual function should also be investigated, particularly in patients who already have cognitive impairment," they add.

"For most drugs with anticholinergic potential an alternative is available. Combinations of drugs with strong anticholinergic activity, such as thioridazine and amitriptyline, should obviously be avoided," the authors advise.

Journal of the Royal Society of Medicine