Antipsychotic Adherence Data Counter Common Belief

A study of 1,686 veterans revealed that the extent of adherence to antipsychotic medication regimens was significantly better than to hypoglycemic and antihypertensive medications, but shorter prescription refill intervals were found to be more closely correlated with nonadherence than were types of medication.

“With adjustment, we found that people with schizophrenia are not any worse about sticking to their medications than people without schizophrenia,” lead study author John Piette, Ph.D., an epidemiologist and an associate professor of internal medicine at the University of Michigan, told Psychiatric News. The study appeared in the February Psychiatric Services.

Piette and four colleagues, all affiliated with Health Services Research and Development in the Department of Veterans Affairs in Ann Arbor, used data from the VA National Psychosis Registry, part of a unified electronic medical record system. The researchers excluded patients who were on more than two hypoglycemic and antihypertensive drugs.

They evaluated prescription-refill data for Fiscal 2002 of patients with a diagnosis of schizophrenia or schizoaffective disorder and both diabetes and hypertension. Most patients were male (95 percent). About 52 percent were white, 29 percent were black, and 11 percent were Hispanic. Each group used an average of 5.3 medications.

Before adjustment, the researchers found that patients appeared to adhere more closely to their antidiabetic and antihypertensive medications than to their antipsychotic drugs. However, once they controlled for characteristics of medication regimens, including average days' supply of drugs, the odds of poor adherence were reversed.

“The adjusted odds of poor adherence were significantly higher for hypoglycemic and antihypertensive medications than for antipsychotic medications,” they wrote.

In fact, the shorter the hypoglycemic and antihypertensive medication refill periods were, the worse the adherence.

“Regimens with an average 30 days' supply or less were associated with a 3.3-fold increase in the relative odds of non-adherence compared with a supply of 60 days or more.”

Drugs to treat diabetes or high blood pressure are usually prescribed in 90-day allotments, and this study showed that the type of medication is heavily correlated with the number of days' supply in the refills, said Piette.

“Antipsychotic drugs are less likely to be filled on time because of obstacles [the patient faces] in getting a prescription filled—like going to the doctor, taking off work, finding transportation, and so on,” he said. “Often we think about adherent patients versus nonadherent patients. But this study is a reminder that a patient's adherence is not consistent across all medications and can depend on other factors like refill intervals.”

“Common wisdom holds that psychiatric patients should get only 30-day supplies of their prescriptions to better maintain watch over symptoms, drug response, and side effects,” said John Newcomer, M.D., a professor of psychiatry, psychology, and medicine and medical director of the Center for Clinical Studies at Washington University School of Medicine in St. Louis, in an interview. “Yet in the study, when refill intervals were held constant [for both the schizophrenia medications and the diabetes and hypertensive medications], there was better adherence to antipsychotic medications.”

Whether this holds true all the time requires more research, said both Piette and Newcomer. Finding the crossover point between shorter and longer refill times demands both knowledge and judgment.

“I suspect it varies by patient characteristics,” said Newcomer. “If you have a suicidal patient, maybe a shorter interval makes sense, but others may find a longer interval beneficial.”

Conventional thinking has also favored treating psychiatric illnesses first as a way of overcoming the memory problems and attentional difficulties they cause, then tackling conditions like diabetes and high blood pressure.

However, medical comorbidities cannot be solved by simply writing a prescription for antidiabetic or antihypertensive drugs, said Newcomer, who has studied the metabolic consequences of psychiatric drugs. Stabilizing a patient on antipsychotics before tackling diabetes and hypertension may not make sense, he said.

“The most important thing to realize now is that adherence problems extend to diabetes and high blood pressure medications,” he said.“ it's naïve to believe that diabetes treatment is 'easy.' It's probably more difficult than administering psychotropics.”

Piette's study should promote greater interest in primary prevention, said Newcomer.

“In psychiatric patients, preventing diabetes is simpler than managing it or other complex diseases. Also, secondary prevention of the metabolic effects is not as easy as many people think. There are adherence and financial challenges to making it work.”

Another study in the same issue of Psychiatric Services found that people with co-occurring psychotic and substance abuse disorders were four times more likely to die over a 12-year period if they also had diabetes.

“Psychiatrists, like all physicians, should encourage patients to take their medications as prescribed,” said Piette. “But this means more than just asking 'Do you take your medications?' The question must be posed for each drug the patient has been prescribed.”

“Differential Medication Adherence Among Patients With Schizophrenia and Comorbid Diabetes and Hypertension” is posted at<http://ps.psychiatryonline.org/cgi/content/full/58/2/207>.▪