Genetic testing to tailor heart drug prescriptions?

Most genetic tests focus on your odds of developing certain diseases or health conditions. But some — known as pharmacogenomic (or pharmacogenetic) tests — can reveal how your body may respond and react to different medications. To date, researchers have identified more than 400 genetic variations known to affect the metabolism of numerous drugs, including some that help lower cholesterol or prevent blood clots (see “Pharmacogenomics of common heart drugs”).

In theory, knowing how people metabolize specific drugs could help doctors choose the safest, most effective treatment for their patients. But in practice, it’s not that straightforward, says Dr. Jason Vassy, assistant professor of medicine at Harvard Medical School and a primary care physician at the VA Boston Healthcare System.

Pharmacogenomics of common heart drugsThe Clinical Pharmacogenetic Implementation Consortium publishes guidelines to help doctors understand how available genetic test results might be used to optimize drug therapy. Here’s a summary of information on two common heart drugs.Simvastatin (Zocor) is prescribed to reduce high cholesterol. Variants in a gene called SLCO1B1 are linked to a rare form of muscle pain (myopathy) caused by statins. Most people have two normal versions of the gene and are unlikely to be at risk. About one-third of people have one or two copies of the risky variant. That doesn’t mean they will definitely develop myopathy — just that they are at higher risk. For example, even if you’re among the estimated 2% of the population who has two copies of the risky variant, your odds of developing statin-induced myopathy are only about 17 in 1,000. But as a precaution, people with copies of the risky variants should take simvastatin only at doses up to 40 milligrams daily or take an alternative statin. The SLCO1B1-myopathy association may also apply to atorvastatin (Lipitor), but that remains unclear for now.Clopidogrel (Plavix) is prescribed to prevent blood clots following a heart attack or stent implantation. Variants of a gene called CYP2C19 affect how well a person converts clopidogrel to its active form in the body. Most people are ultra-rapid metabolizers and therefore get the desired effectiveness. But about 30% of people are intermediate or poor metabolizers, meaning the drug is less effective, potentially leaving them at higher risk for dangerous clots. People with such variants might benefit from an alternative anti-clotting drug, such as prasugrel (Effient) or ticagrelor (Brilinta).

No clear benefit

“Simply knowing about a drug-gene association isn’t enough to show whether that information will improve a person’s health,” he says. So far, there’s no clear evidence of a benefit for the average person who has or is at risk for heart disease.

That’s also the case for pharmacogenomic tests for psychiatric drugs, which have been marketed directly to consumers in recent years. Although some studies have suggested possible benefits, the FDA says these tests have no proven value. The problem? Many other factors — including age, sex, when and what you last ate, and other drugs you take — can affect drug levels in your body.

New information from old results

More than a million people have already taken a psychiatric pharmacogenomic test (according to one of the industry’s leading companies) and may therefore know the makeup of some of their genotype — including their CYP2C19 gene, which regulates an enzyme that affects the breakdown of certain antidepressants, as well as some other drugs, including the anti-clotting agent clopidogrel (Plavix). And more than 10 million people have ordered testing from the direct-to-consumer genetic testing company 23andMe. Some of its packages include pharmacogenomic information about CYP2C19 and another gene of interest called SLCO1B1.

“If you have pharmacogenomic information from one of these tests, it’s worth sharing with your primary care physician and cardiologist,” says Dr. Vassy. For example, if you had a heart attack, you might need a stent, a tiny mesh tube to prop open a blocked heart artery. Normally, your doctor would then prescribe clopidogrel to discourage clots. But if you know you’re a poor responder, he or she might consider prescribing an alternative drug (which isn’t done routinely for cost reasons).

Similarly, pharmacogenomic results for the SLCO1B1 gene can give some information about the risk of muscle side effects from one common statin, simvastatin (Zocor), and possibly atorvastatin (Lipitor). But it probably doesn’t apply to other statins. Further research is needed before pharmacogenomic tests are used in routine visits for heart-related conditions.

Bible verses for today’s meditation and inspiration: Matthew E. McLaren’

Then you will call on me and come and pray to me, and I will listen to you. Jeremiah 29:12 NIV

Be joyful in hope, patient in affliction, faithful in prayer. Romans 12:12 NIV

And when you pray, do not keep on babbling like pagans, for they think they will be heard because of their many words. Matthew 6:7 NIV

The Lord is near to all who call on him, to all who call on him in truth. Psalm 145:18 NIV

‘Call to me and I will answer you and tell you great and unsearchable things you do not know.’ Jeremiah 33:3 NIV

“For where two or three gather in my name, there am I with them.” Matthew 18:20 NIV

 Let us then approach God’s throne of grace with confidence, so that we may receive mercy and find grace to help us in our time of need. Hebrews 4:16 NIV

who is unseen. Then your Father, who sees what is done in secret, will reward you. Matthew 6:6 NIV

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