Genetic testing is becoming the preferred practice when prescribing psychiatric medications, as these tests reduce the risk for treatment failure and serious side effects, according to Dr James Kennedy, Director of the Neuroscience Research Department, Section Head of the Psychiatric Neurogenetics lab and Head of the Tanenbaum Centre for Pharmacogenetics at the Centre for Addiction and Mental Health, Toronto.
“Adverse drug reactions are responsible for between 5% and 7% of hospital admissions across the United States and Europe, lead to the withdrawal of 4% of new medicines and cost society an amount equal to the costs of drug treatment,” Kennedy said. “Identifying genetically poor metabolizer patients may prevent a meaningful portion of adverse reactions.”
Moreover, genetic testing leads to significant cost savings. “A physician can try and use the so-called normal dose, but because there is diversity in how patients respond to medications, it is significantly better if the physician has information on each patient’s specific genes in the liver that control the breakdown of these medications,” he said. “The physician should know which of these genes are working in a fast, slow or semi-normal manner.”
According to the findings of a 2014 study published in the journal International Clinical Psychopharmacology, where he and colleagues systematically reviewed the societal and economic burden of treatment-resistant schizophrenia among patients included in 65 studies published between 1996 and 2012, there was an overall 4% incidence of severe adverse events to treatment, and mean quality of life for patients who were unresponsive or intolerant to treatment was 20% lower than that of patients in remission. The annual costs for patients with treatment-resistant schizophrenia were estimated at 3- to 11-fold higher than those with treatable schizophrenia.
“Treatment-resistant schizophrenia remains common and costly, despite availability of many treatment options, and contributes to a significant loss in patient quality of life,” they wrote. “Although estimates in the literature vary greatly, treatment-resistant schizophrenia conservatively adds more than $34 billion in annual direct medical costs in the United States.”
According to Kennedy, “Genetic testing has come a long way in recent years. My hope for the future lies in understanding the genes in the brain better. The genetic variation in the liver is becoming better understood, but we still do not know how the liver genes interact exactly. We are now investigating genes in the brain, which is significantly more complicated than the liver and so far we have received interesting and useful answers.”
Kennedy and colleagues are also examining a group of genes from the appetite centre in the brain that predict which patients will experience weight gain while taking some of the newer antipsychotic medication. “The tests of the brain appetite gene are looking quite good and we are hoping they will get applied in clinical practice to prevent weight gain, which can also lead to diabetes and heart disease,” he said. “Beyond this, getting a much better assessment of the genes in the brain that control all the aspects of response in terms of how fast patients respond to treatment and in terms of whether additional therapies may be helpful, such as psychotherapy or electrical brain stimulation, are interesting questions for the future.”