The discoveries in human genetics have led to the understanding that genetic mutations, called variants, can play a major role in predicting how a patient will respond to certain medications. This science known as pharmacogenetics is just now making its way from academic institutions into the physician's office using recent advancements in genetics and bio- informatics.
The tool revolves around the idea of a genetic testing service that provides the necessary interpretive information to help physicians understand the implications and outcomes of a patient's genetic test results.
Reggie Downey vice-president of Seryx, the company that provides the service, said: "For each patient results from a medical history questionnaire, a multi-gene analysis and clinical co-factors are evaluated against the latest scientific knowledge to produce the Signature Genetics interpretive report."
"Signature Genetics is designed to assist physicians in customising drug prescriptions based on an individual patient's unique genetic makeup, as well as to identify drug combinations which can cause harmful interactions. Once a cheek swab and medical history questionnaire are sent to the laboratory, a Signature Genetics report is sent to the physician's office within 15 business days."
Personalised drug therapy is especially important in psychiatry where variations in the CYP2D6 gene play an important role in treatment success. It provides a better understanding of which drugs, drug dosage and/or drug combinations will be effective or problematic.
When multiple drugs are given to a patient, one drug may interfere with the metabolism of another drug, sometimes rendering the second drug useless or potentially toxic. The genetic assessment also assists physicians to identify which drug combinations can be problematic for the patient.
According to Seryx, Approximately 7 to 10 per cent of Caucasians will have some form of genetic variants affecting drug response. These individuals' genetic makeup will consists of two copies of a variant gene rendering them poor metabolisers. Such patients will metabolise drugs too slowly and accumulate in the body to potentially toxic levels.
Drugs that can be influenced by genetic variations include antidepressants, antipsychotics, Antihistamines, Antiarrhythmics, Barbiturates, Beta-blockers, Cardiovascular drugs and certain Chemotherapeutic Agents.
For some drugs such as Codeine, patients with genetic variants will experience no pain relief. These individuals' genetic makeup prevents them from producing the enzyme required to convert codeine into morphine, the active pain-relieving agent of codeine.
The metabolism of a drug called Warfarin (Coumadin), a blood anticoagulant, is also heavily impacted by genetic variations. In this case, incorrect dosages can lead to serious, even fatal, side effects.