HealthDay News — For older patients treated with cholinesterase inhibitors, taking antipsychotic agents for dementia is associated with a modest and time-limited increased risk of myocardial infarction (MI), study data indicate.

“Because AP use is frequent in patients with dementia (29.5% in our study population), the increased risk of MI may have a major public health effect, which highlights the need for communicating such risk and for close monitoring of patients during the first weeks of treatment,” Antoine Pariente, MD, PhD, of the Université de Montreal, and colleagues reported in Archives of Internal Medicine.

They retrospectively identified a cohort of 37,138 community-dwelling older patients, who initiated cholinesterase inhibitor treatment, based on the Quebec, Canada, prescription claims database from 2000 through 2009. The cohort included 10,969 new antipsychotic users who were matched with a random sample of antipsychotic nonusers.

Continue Reading

Within one year of initiating antipsychotic treatment, 1.3% of new users had an incident MI. There was an increased risk of MI after initiation of antipsychotic treatment, with a hazard ratio of 2.19 in the first 30 days (95% CI: 1.11-4.32), 1.62 in the first 60 days, 1.36 in the first 90 days, and 1.15 for the first year.

“The increased risk seems to be highest at the beginning of treatment and seems to decrease thereafter, with the first month of treatment accounting for the highest period of risk,” the researchers wrote.

The incidence rate ratios In a self-controlled case series study conducted among a subset of 804 new antipsychotic users who experienced incident MI, incidence rate ratios were 1.78 for the one- to 30-day period (95% CI, 1.26-2.52), 1.67 for the 31- to 60-day period, and 1.37 for the 61- to 90-day period.

The researchers warned that the observed risk was small and may only represent residual confounding or hidden bias. They called for more clinical trials with larger sample sizes to identify high-risk subpopulations.

In an accompanying editorial, Sudeep S. Gill, MD, MSc, and Dallas P. Seitz, MD, both of Queen’s University, in Kingston, Ontario, Canada, said that the findings may hold important lessons about the pathogenesis of cardiovascular disease, but that further research is necessary to determine the underlying mechanisms of the observed association between antipsychotic drug use and acute MI.

“Meanwhile, physicians should limit prescribing of antipsychotic drugs to patients with dementia and instead use other techniques when available, such as environmental and behavioral strategies, to keep these patients safe and engaged,” Gill and Seitz wrote.

Pariente A et al. Arch Intern Med. 2012;doi:10.1001/archinternmed.2012.28.

Gill SS, Seitz DP. Arch Intern Med. 2012;doi:10.1001/archinternmed.2012.682.