A new study finds that older people taking a drug used to treat anxiety and insomnia — nitrazepam — as well as those on antidepressants, are twice as likely to suffer postoperative delirium after hip and knee surgery.

The finding has prompted calls by University of South Australia (UniSA) researchers for older patients to temporarily cease these medications or change to safer alternatives prior to surgery.

In a study published in the international journal Drug Safety, UniSA scientists scanned data from 10,456 patients aged 65 years and older who had undergone knee or hip surgery in the past 20 years. A quarter of them (2614 people) had experienced delirium after surgery.

Apart from nitrazepam and antidepressants, five other medications — commonly prescribed for anxiety, seizures and insomnia — were associated with delirium, although not to the same extent. They included sertraline, mirtazapine, venlafaxine, citalopram and fluvoxamine.

Lead researcher Dr Gizat Kassie says there was no link between pain-relieving opioids and delirium.

«Our findings show that different classes of medicine are riskier than others when it comes to causing delirium after surgery, and the older the patients are, the greater the risk,» he says.

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