Two antipsychotic drugs commonly used to treat delirium did not benefit critically ill patients in intensive care units who took part in a recent clinical study funded by the National Institute on Aging of the National Institutes of Health.

The researchers found no evidence that treatment with haloperidol or ziprasidone affected delirium, survival, length of ICU or hospital stay or safety. Findings from the Modifying the Incidence of Delirium USA, or MIND USA, study were published online Monday in the New England Journal of Medicine.

“This is strong evidence from what we consider a ‘gold standard’ clinical trial showing that these two antipsychotics don’t work to treat delirium during a critical illness,” NIA Deputy Director Marie A. Bernard, M.D., said in a statement. “Antipsychotics have often been used to treat delirium. The evidence from this study suggests the need to re-examine that practice.” Bernard is also NIA’s senior geriatrician.

The study included almost 21,000 patients at 16 U.S. medical centers.

Antipsychotic medications have been used to treat delirium in ICUs for more than four decades. Delirium can affect people of any age but is more common among older adults who experience major illness or have major surgery, the researchers noted.

Delirium causes people to feel disoriented, withdrawn or drowsy or makes them difficult to wake. It is associated with higher hospital costs and multiple adverse outcomes, such as longer hospital stays, long-term cognitive impairment and death.

Some evidence exists that medications such as dexmedetomidine or melatonin — which are being studied in separate NIA-funded grants to other researchers — may reduce both the prevalence and duration of delirium, the researchers said. Reducing oversedation and improving early mobility is another strategy, they added.