Genetic Testing and Pharmacogenomics: How Your DNA Can Guide Better Treatment

You have been prescribed a medication. You take it as directed for four weeks. Nothing improves. Your provider increases the dose. Still nothing — or now you have side effects. A new medication is tried. Then another. Months pass. You begin to wonder whether any of this is working, or whether medicine is just guessing.

For many patients, this trial-and-error process is not an exaggeration. It is exactly how medication management has historically worked: prescribe the standard first-line agent, wait, assess, adjust, switch. For some conditions — depression, chronic pain, cardiovascular disease, diabetes — patients may cycle through three, four, or five medications before finding one that works without intolerable side effects.

Pharmacogenomics offers a different approach. It uses your DNA to predict, before you take a single dose, how your body is likely to respond to specific medications. It does not replace clinical judgment. But it gives your provider a map where, previously, there was only a compass.

I’m Dr. Aisha Williams, a board-certified endocrinologist at Moses Medical Center. I trained at Howard University College of Medicine, completed my residency at Harlem Hospital Center, and did my fellowship in endocrinology at Albert Einstein College of Medicine and Montefiore Medical Center. I have a particular interest in genetic testing — both pharmacogenomics and hereditary risk assessment — because I have seen firsthand how it changes outcomes for patients who were stuck in the trial-and-error cycle.

What Pharmacogenomics Actually Is

Pharmacogenomics is the study of how genetic variations affect your response to medications. Your DNA contains instructions for building the enzymes that metabolize drugs in your liver, the receptors that drugs target in your body, and the transporters that move drugs between tissues.

Variations in these genes can make you:

• A rapid metabolizer — your body breaks down the drug too quickly, so it never reaches therapeutic levels. The standard dose is essentially ineffective for you.
• A normal metabolizer — the drug works as expected at standard doses. This is what the prescribing guidelines assume.
• A poor metabolizer — your body breaks down the drug slowly, so it accumulates. The standard dose may cause exaggerated effects or serious side effects.

These are not rare anomalies. Approximately 90% of people carry at least one genetic variation that affects how they process medications. This is not about being genetically abnormal — it is about recognizing that one-size-fits-all dosing is biologically inaccurate.

Clinical Scenarios Where Pharmacogenomics Matters Most

Depression and Anxiety Medications

This is the area where pharmacogenomics has the most robust evidence and the most immediate clinical impact. SSRIs like sertraline (Zoloft) and escitalopram (Lexapro) are metabolized by liver enzymes CYP2C19 and CYP2D6. Genetic variations in these enzymes are common and significantly affect drug levels:

• A CYP2C19 rapid metabolizer may not achieve therapeutic levels of escitalopram at standard doses, leading to treatment failure that looks like medication-resistant depression — but is actually a dosing problem.
• A CYP2D6 poor metabolizer may experience severe side effects from fluoxetine (Prozac) because the drug accumulates to toxic levels at standard doses.

For patients starting antidepressants, pharmacogenomic testing can identify the right medication and the right dose from the beginning — potentially sparing months of ineffective treatment. Our behavioral health team, including Dr. Emmanuel Okafor, uses pharmacogenomic results to guide prescribing decisions when available. Dr. Okafor has written about the mental health crisis in the South Bronx and how cultural barriers keep patients from seeking care.

Pain Management

Codeine is a prodrug that must be converted to morphine by the CYP2D6 enzyme to be effective. Poor metabolizers get essentially no pain relief from codeine. Ultrarapid metabolizers convert codeine to morphine too quickly, risking respiratory depression and overdose. Tramadol has a similar metabolic profile.

For patients with chronic pain, knowing their CYP2D6 status before prescribing can prevent both treatment failure and dangerous adverse events.

Cardiovascular Medications

Clopidogrel (Plavix), a blood thinner used after heart attacks and stent placement, requires CYP2C19 activation to work. Approximately 25-30% of patients are poor metabolizers who get reduced or no benefit from clopidogrel — putting them at higher risk for blood clots. For these patients, an alternative antiplatelet medication is the safer choice.

Statins (cholesterol-lowering medications) are affected by variations in the SLCO1B1 transporter gene. Certain variants increase statin levels in the blood, raising the risk of muscle damage (myopathy) — one of the most common reasons patients stop taking their cholesterol medication.

Warfarin, a widely used blood thinner, is affected by variations in CYP2C9 and VKORC1 genes. Pharmacogenomic-guided warfarin dosing reduces the time to therapeutic range and decreases the risk of both bleeding and clotting complications. Patients with cardiovascular concerns should also read our guide on when to see a cardiologist.

Diabetes Management

As an endocrinologist, I see the potential here clearly. Genetic variations affect the response to metformin (the first-line diabetes medication), sulfonylureas, and other glucose-lowering agents. While pharmacogenomic testing for diabetes medications is still emerging compared to psychiatry and cardiology, the science is advancing rapidly, and I use available data to inform treatment decisions for complex patients. For diabetic patients, uncontrolled blood sugar impairs wound healing — a complication addressed in our diabetic wound care program.

How Testing Works at Moses Medical Center

The testing process is simple:

1. Pre-test counseling. Before any genetic test, I explain what the test can and cannot tell you, how results will be used, and what the implications might be. Informed consent is essential — this is your genetic information, and you deserve to understand it fully.

2. Sample collection. Pharmacogenomic testing requires either a blood draw or a buccal swab (a painless cheek swab). If blood is drawn, it is processed through our on-site lab. Samples are sent to a certified reference laboratory for analysis.

3. Results (typically 7-14 days). You receive a detailed report that categorizes your metabolizer status for each relevant enzyme and maps those results to specific medications. The report includes actionable recommendations — not just data, but clinical guidance.

4. Results review. I sit down with you to review every finding, explain what it means for your current medications, and adjust your treatment plan accordingly. If a medication change is needed, we make it that day. If a compounded formulation at a specific dose would be optimal, we can coordinate with our specialty compounding partners.

Who Should Consider Pharmacogenomic Testing

Pharmacogenomic testing is most valuable if:

• You have tried multiple medications for the same condition without success
• You have experienced significant side effects from standard-dose medications
• You are starting treatment for depression, anxiety, or chronic pain and want to avoid the trial-and-error process
• You take multiple medications (polypharmacy) and want to minimize interactions
• You have a family history of unusual drug reactions
• You are starting clopidogrel, warfarin, or statin therapy and want optimized dosing from the start

Beyond Pharmacogenomics: Other Genetic Tests We Offer

At Moses Medical Center, our genetic testing program also includes:

• Hereditary cancer risk assessment — for patients with a family history of breast, ovarian, colorectal, or other cancers. Identifying BRCA1/2 mutations or Lynch syndrome early enables proactive screening and risk reduction.
• Carrier screening — for individuals or couples planning a family. We test for sickle cell trait, cystic fibrosis, Tay-Sachs disease, and other inherited conditions that are especially relevant in the diverse populations of the Bronx.
• Hereditary endocrine conditions — including genetic forms of thyroid disease, familial hypercholesterolemia, and rare metabolic disorders.

Insurance Coverage

Pharmacogenomic testing is increasingly covered by insurance when there is a documented medical necessity — such as treatment failure on multiple medications or a serious adverse drug reaction. MetroPlus, Fidelis Care, and other Medicaid managed care plans cover genetic testing with prior authorization when clinical criteria are met. Our team handles the authorization process.

For patients whose insurance does not cover testing, many reference laboratories offer patient assistance programs that cap out-of-pocket costs at $100-$300 regardless of list price. We will always discuss cost before ordering any test.

Medicine Should Be Personal

The Human Genome Project was completed over two decades ago. The science of pharmacogenomics has been validated in thousands of studies. And yet, most patients in the Bronx have never been offered a test that could spare them months of ineffective treatment and unnecessary side effects.

At Moses Medical Center, we are changing that — one patient at a time.

Book an appointment with Dr. Williams or call (646) 741-2111. We are at 871B Westchester Ave, Bronx, NY 10459. Your DNA has answers. Let us help you read them.