TORONTO - Seniors with diabetes who are given antipsychotic drugs to control symptoms of dementia have an increased risk of ending up in hospital with potentially dangerous high blood sugar levels, researchers say.
A large study of older Ontario diabetics found that those who were newly treated with an antipsychotic medication were 50 per cent more likely to be hospitalized for high blood sugar, or hyperglycemia, compared to those who were not taking one of the drugs.
"This indicates that patients with diabetes are more vulnerable to sudden worsening of their glucose control during the initiation of antipsychotic drugs," says principal investigator Dr. Lorraine Lipscombe, an endocrinologist at Women's College Hospital in Toronto.
"This is particularly significant for the elderly because they are the biggest group of patients with diabetes and are already the most vulnerable to poor diabetes control."
Lipscombe, who is also a researcher at the Institute for Clinical Evaluative Sciences, said the greatest risk appears to be right after a patient takes the first prescription for an antipsychotic.
And surprisingly, the effect on blood sugar levels occurred with both classes of antipsychotic medications, which are known as typical and atypical.
Older, typical antipsychotics include chlorpromazine (Largactil, Thorazine), fluphenazine (Prolixin) and haloperidol (Haldol, Serenace). Newer, atypical drugs include clozapine (Clozaril, Clopine and other brand names), risperidone (Risperdal, Ridal and others) and quetiapine (Seroquel, Ketipinor).
"There has been a lot of focus on the atypical antipsychotics among younger people with schizophrenia because there is some evidence that it may increase the risk of diabetes," she said.
"We were interested first of all in whether it worsens diabetes control in people who already had it. But what was surprising to us was that all the antipsychotics increased the risk of hyperglycemia, not just the atypicals."
The study, published in this week's issue of the Archives of Internal Medicine, examined health and prescribing records for 13,817 diabetics in Ontario, aged 66 and older, who started antipsychotic treatment between April 1, 2002 and March 31, 2006 and were followed for an average of two years.
In all, 1,515 (11 per cent) were hospitalized for high blood sugar. Of those, 24 per cent were being treated with insulin, 13 per cent were on oral medications and almost four per cent were receiving no drug treatment.
Lipscombe said the new finding adds to concerns about the drugs, some of which already carry safety warnings after they were found to increase the risk of stroke and death in older people.
"First of all, the use of these drugs has increased dramatically over the last decade among seniors, largely to control the behavioural symptoms of dementia," she said. "This has been a relatively new use for these drugs in a new population."
"It's not clear what the mechanism is, but it's caused sufficient concern such that warnings have been issued to be extra cautious when using these drugs in this population."
It had been thought that because the drugs can cause weight gain, that in turn might lead to diabetes and high blood sugar levels. But the fact that the effect occurs so soon after starting the medications has called that theory into question, she said.
It may be that the drugs, which inhibit dopamine secretions in the brain, are acting on the body's glucose control centre, she hypothesized. "There needs to be a lot of research before we can say that for sure."
Dr. Gary Remington, an expert in antipsychotics and schizophrenia at the Centre for Addiction and Mental Health in Toronto, said the study "adds an important piece to the puzzle."
He said the medications, which have a calming, sedating effect, are the current treatment of choice for psychotic behaviours in people with schizophrenia and dementia. Those behaviours commonly include aggression, which can be worsened by feelings of paranoia.
But because of their unwanted side-effects, scientists are looking for new drugs as alternatives to antipsychotics, said Remington, who was not involved in the study.
Lipscombe said that if antipsychotic drugs are prescribed for a diabetic with dementia, family members and health-care providers need to keep an eye on the person for signs of rising blood sugar.
Those signs include lack of appetite, increased thirst and urination, confusion and diminished consciousness. In some cases, the person could become comatose if the spike in blood sugar isn't caught and treated, she said.
"It doesn't mean that people shouldn't be treated with these drugs, it means that people need to be aware and monitored closely so they can avert hospitalization," she said. "We simply feel that people need to be more aware of the safety issues and be prepared to manage them early."
Remington said all people taking the drugs, no matter their primary diagnosis, need to be regularly evaluated for adverse effects.
"What it really reminds clinicians - which is one of the take-home messages from this study - is that you have to begin to monitor these people right from the outset of treatment."
