A synthetic cannabis drug used to treat nausea in cancer patients may also help calm agitation in patients with Alzheimer’s disease, researchers reported Tuesday.

Agitation is one of the most troubling symptoms of Alzheimer’s, and can be difficult to manage. It’s the reason some dementia patients are given antipsychotic drugs or even physically restrained, steps that go against medical advice.

Sedatives, anxiety drugs and other medications are also often given to patients.

“Agitation, aggression, sleep disturbances — all have a significant impact on both their quality of life and their carers’ quality of life,” said Heather Snyder, senior director of medical operations for the Alzheimer’s Association.

Doctors have long been looking for a drug that could safely treat agitation in Alzheimer’s patients.

“Currently prescribed treatments for agitation in Alzheimer’s do not work in everybody, and when they do work the effect is small and they increase risk of harmful side effects, including increased risk of death,” Krista Lanctôt of Sunnybrook Health Sciences Center and the University of Toronto, who led the research, said in a statement.

“As a result, there is an urgent need for safer medication options.”

Lanctôt’s team tested nabilone, a synthetic form of cannabis approved in the U.S. for treating nausea caused by chemotherapy, and used in Canada to treat pain.

For six weeks, they gave the pill to 39 patients with dementia, then gave them a placebo for six more weeks.

"Agitation improved significantly in those taking nabilone, compared to placebo,” the Alzheimer’s Association said in a summary of the research being presented at its annual meeting in Chicago.

“Nabilone also significantly improved overall behavioral symptoms, compared to placebo, as measured by the Neuropsychiatric Inventory" questionnaire.

However, the drug made patients drowsy. Lanctôt’s team said 45 percent of the patients they treated were noticeably drowsy when they took nabilone. And because it is a synthetic copy of THC, the high-producing chemical in marijuana, it caused other effects, also.

“It does have some of the euphoric, drowsiness effect,” Snyder told NBC News. “There are safety concerns.”

The Alzheimer’s Association made a point of saying that it does not recommend simply giving marijuana to Alzheimer’s patients.

“Nabilone is not the same. It is a synthetic cannabinoid made using one specific component. There are controls on the quality. There are controls on the dose,” Snyder said.

“Currently, marijuana is, essentially, an untested drug in Alzheimer’s. Its potential effectiveness and safety profile have not been thoroughly evaluated in clinical trials for people living with (or at risk for) Alzheimer’s disease dementia,” the association added in a statement.

But if larger studies showed that nabilone was safe, it would fill “a huge unmet medical need,” said Dr. Howard Fillit, founding executive director and chief science officer of the Alzheimer’s Drug Discovery Foundation, who was not involved in the research.

“The results of this research are very encouraging, especially given the numerous failures in the field to date,” Fillit said in a statement.

“The use of synthetic cannabinoids is a novel approach in the treatment of agitation in patients with Alzheimer’s," he said. "There is great interest and excellent scientific rationale for the use of cannabinoids in Alzheimer’s that might include a disease-modifying effect that can be tested in subsequent studies.”

Other teams have tried testing cannabis-like drugs in Alzheimer's. In 2003, a different Canadian team tested Marinol, which is similar to nabilone, in some patients and found that it reduced agitation and helped them gain weight. But there have been doubts about the safety of the drugs.

Meanwhile, the Alzheimer’s Association has some advice for caregivers of patients with dementia who become agitated:

Validate that the person seems to be upset over something.

Separate the person from what seems to be upsetting.

Engage in regular physical activity to potentially reduce irritability and aggressive behavior.

Assess for the presence of pain, constipation or another physical problem.

Medications can have unexpected effects in patients with Alzheimer’s. A British team looked at the effects of several sleep aids on dementia patients, and found that the drugs made patients more likely to fall down and break a bone. The drugs are known as “Z-drugs” because their generic names begin with the letter Z: Ambien, known generically as zolpidem; Sonata, known generically as zaleplon; and zopiclone, a generic drug similar to Lunesta.

The British study, which involved nearly 3,000 patients, found a 40 percent increased risk of a fracture when patients took any of the drugs.

“Fractures in people with dementia can have a devastating impact, including loss of mobility, increased dependenc, and worsening dementia,” said Dr. Chris Fox, a psychiatry professor at the Norwich Medical School of the University of East Anglia in Britain.

“We desperately need better alternatives to the drugs currently being prescribed for sleep problems and other non-cognitive symptoms of dementia,” Fox said in a statement.