ST. LOUIS — Leslye Nathe did not realize the profound effect that Ritalin was having on her mother’s Alzheimer’s disease until a doctor stopped the prescription.

Her mother, Susan Brown, 74, a resident at Provision Living in Webster Groves, Mo., began sleeping nearly all the time. And during rare moments, when she was awake, she was tearing the sheets off her bed and scratching wounds into her arms.

“She was like a child having a tantrum and she kept telling people to leave. She was very paranoid,” Nathe said. “She would beg me, ‘Please, please get me some medication. There’s something wrong. I can’t deal with it anymore.’”

Brown had been taking Ritalin for many years even before she was diagnosed with Alzheimer’s, to treat attention deficit disorder and depression.

When her physician, Dr. George Grossberg, director of geriatric psychiatry at St. Louis University, heard about her alternating bouts of lethargy and meltdowns, he put Brown back on the Ritalin.

Her reaction to being taken off the drug was more extreme than usual, but it supported the long-held notion that Ritalin is key to controlling some Alzheimer’s symptoms.

Grossberg and a team of researchers at the university, recently received a $183,540 grant from Noven Pharmaceuticals Inc. to study Ritalin as a therapy for apathy and fall risk in Alzheimer’s patients. Both are common symptoms of Alzheimer’s disease, affecting about 70 percent patients who have it.

Noven is a joint-venture partner of Novartis Pharmaceuticals, which manufactures Ritalin. Novartis paid Grossberg $28,000 in 2010 to speak about its products to other physicians.

Grossberg said family members frequently notice that loved ones are indifferent, socially disengaged and have lost all enthusiasm.

“It’s serious couch-potatoism, and it drive relatives crazy,” Grossberg said. “There’s a lot of evidence that Ritalin has mood-elevating effects and also makes them more aware of their environment and obstacles. They also make better decisions.”

Scientists are not sure what causes apathy in patients with Alzheimer’s disease but early data indicate that it might be related to a decrease in the transmission of dopamine, a feel-good chemical in the brain. Ritalin, which is commonly used to treat attention deficit disorder, increases the transmission of dopamine in the brain.

A previous international clinical trial, funded by the National Institute on Aging, showed marked improvements on clinical testing for apathy among Alzheimer’s patients who were given Ritalin compared to those who were not.

“Once you have depression, or apathy in this case, it makes it harder to focus on the environment,” Grossberg said. “So by improving patients’ energy levels, we think it will contribute to them being less likely to fall.”

Falling and balance do not involve the hippocampus, which is most responsible for memory and most profoundly affected by the disease.