A commonly-used antipsychotic drug used to treat delirium in critically ill patients is not very effective, according to new research.

The researchers claim that the drug haloperidol is no more effective than placebo in reducing the number of days patients spend either delirious or in a coma.

Patients who are critically ill often have symptoms of delirium, where the patient can be seriously confused and disoriented.

Doctors at Watford General Hospital in England tested haloperidol on 141 critically ill patients on artificial breathing- half of them were given the drug and the remainder a 'sugar pill' or placebo.

It was found that, up to 14 days after the study commenced, compared to the placebo patients, haloperidol had no effect on the number of days patients spent without delirium and not in a coma.

The antipsychotic medication also had no effect, it was found, on death rates of seriously ill patients, length of stay in a critical care unit, or the number of days the patient was not placed on a ventilator.

Usually, critically ill people who become delirious are at increased risk of death. Delirium also adds to the discomfort experienced by the seriously ill patient.

The researchers did find, however, that haloperidol can help sedate agitated patients in the short-term.

The research is published in The Lancet Respiratory Medicine.