New research into the risks of three common antipsychotic drugs for the elderly suggests older patients are 73 percent more likely to experience acute kidney injury (AKI) while on any of the three medications.

The research, published in the August 19 issue of the Annals of Internal Medicine, examined the medical records of nearly 100,000 adults 65 and older who were taking any of three common atypical antipsychotic medications: quetiapine, risperidone and olanzapine.

Authors Hwang et al. report that these three drugs are prescribed to millions of older adults per year worldwide. These medications are frequently used to manage behavioral symptoms associated with dementia, the authors write, though the FDA has advisories issued for each drug warning that such use is associated with increased mortality.

Hwang et al. found that patients who had received a prescription for any one of these three medications in the previous 90 days where 73 percent more likely to be hospitalized for AKI, defined as sudden reduction or loss of kidney function. The drugs were also associated with an increased risk of hypotension, acute urinary retention and death. Hypotension and acute urinary retention (the inability to empty one’s bladder) have both been associated with AKI, the researchers report.

Specifically, patients prescribed these drugs were nearly twice as likely to suffer from hypotension and acute urinary retention (91 percent more likely and 98 percent, respectively) and more than twice as likely to die. With this data behind them, the researchers conclude that their findings support the existing safety concerns about the use of these drugs in older adults.

The research also has broader implications regarding the importance of fully understanding an elderly patient’s genetic makeup. All three of the antipsychotic drugs studied are processed through the body’s CYP450 pathway, making them subject to drug-drug and drug-gene interactions. Genetic variations along these lines could drastically affect how a patient metabolizes these medications and could lead to additional adverse drug events.

For example, a large clinical study in 2005 found that CYP2D6 poor metabolizers had 75 percent higher levels of risperidone in their systems compared to CYP2D6 normal metabolizers. Additionally, the study showed a roughly three-fold increase in adverse drug effects and a six-fold increase in discontinuing risperidone because of an adverse effect in CYP2D6 poor metabolizers compared to normal metabolizers.

Pharmacogenetic testing allows prescribers to discover variations in CYP2D6 and other members of the CYP50 pathway family. Such tests, teamed with YouScript, can help physicians prescribe with confidence once they have a complete understanding of their patients’ genetic proclivities in their charts.