Predicting Drug Response

images (92)According to the CDC Adverse drug events are a serious public health problem, an estimated 82% of American adults take at least one medication and 29% take five or more; 700,000 emergency department visits and 120,000 hospitalizations are due to adverse drug events annually.

Three and a half billion dollars is spent on extra medical costs of adverse drug events annually, at least 40% of costs associated with adverse drug events occurring outside hospitals can be prevented.

Often, an effective drug response is found in a few patients treated, while most benefit little or not at all. Much could be gained if we could select the optimal drug for the individual patient before treatment begins.

Researchers are learning how inherited differences in genes affect the body’s response to medications. These genetic differences will be used to predict whether a medication will be effective for a particular person and to help prevent adverse drug reactions.

Just as a patient’s age, lifestyle, existing co-morbidities, and other medications affect the selection of a drug, genetic predisposition to do well or poorly on that drug is a crucial clinical factor that health care providers can now consider.

Case study

There are four main isoforms, or families of mixed-function oxidases known as cytochrome p 450 (CYP450) involved in xenobiotic, or drug metabolism. Cytochrome CYP2C19 is an enzyme that metabolizes some commonly prescribed drugs

Metabolism by CYP2C19 can either activate or alter activity of a drug

– Clopidogrel ( platelet inhibitor) is activated by CYP2C19

– Amitriptyline ( has many psychiatric indications ) is metabolized by CYP2C19 to a less active form

Genetic variations in the CYP2C19 gene may lead to changes in metabolic activity of the CYP2C19 enzyme (increased or reduced function).

What are a person’s odds of having a reduced function of CYP2C19?

Approximately 40% of the population, the exact percentage varies by ethnicity

What can we expect with a low CYP2C19 activity?

Low CYP2C19 activity is associated with diminished antiplatelet response to clopidogrel leading to a higher risk for another heart attack or stroke.

Action: alternate therapy.

Amitriptyline would be associated with a higher incidence of adverse events and toxicity.

Action: start with a lower dose or alternate therapy

Understanding various genes activities will lead to predictable patient outcomes when evaluated with regards to environmental exposures, medical history, family background, and other factors.

There are many community resources available to assist with medication therapy, for no or a small fee you can consult with a qualified healthcare professional to enable you and your healthcare team choose the right medication and the right dose that increases the likelihood of achieving the desired therapeutic effect and reducing the risk of unintended adverse drug reactions.


This entry was posted on January 22, 2016, in Health. Bookmark the permalink.