The Dosing Gap: How Racial and Genetic Disparities in Drug Research Put Patients of Color at Risk

When the Food and Drug Administration approves a medication, the dosing recommendations printed on the label are based on data collected during clinical trials. For much of the twentieth century—and to a troubling degree even today—those trials enrolled populations that were predominantly white and predominantly male. The result is a body of pharmaceutical knowledge that was built on a narrow slice of human genetic diversity and then applied universally.

This is not a minor statistical footnote. It has real consequences for the millions of American patients whose genetic ancestry differs from the populations on which most drugs were tested. Understanding those consequences, and knowing how to raise them in a clinical setting, is an increasingly urgent dimension of patient safety.

Why Genetics Matter in Drug Metabolism

The way the body processes a medication—absorbing it, converting it into active or inactive compounds, and eventually eliminating it—is largely governed by enzymes. The most studied family of these enzymes is called cytochrome P450, or CYP450, a group of liver proteins responsible for metabolizing a vast range of pharmaceuticals.

The genes that encode these enzymes vary across individuals and populations. Some people are "poor metabolizers" of a given drug, meaning the medication lingers in their system longer and at higher concentrations than expected. Others are "ultra-rapid metabolizers," clearing drugs so quickly that standard doses may produce little therapeutic effect. These variations are not random—they cluster along lines of genetic ancestry, and their frequencies differ meaningfully between racial and ethnic groups.

For example, the enzyme CYP2C19 plays a major role in activating clopidogrel, a widely prescribed antiplatelet medication used to prevent blood clots after a heart attack or stroke. Research has found that loss-of-function variants in the CYP2C19 gene occur in approximately 2 to 3 percent of white individuals but in as many as 15 to 20 percent of East Asian patients. Patients carrying these variants who are prescribed standard doses of clopidogrel may receive inadequate antiplatelet protection—a potentially life-threatening gap in treatment.

Documented Disparities Across Drug Classes

Cardiovascular Medications

Cardiovascular pharmacology offers some of the most extensively documented examples of differential drug response. ACE inhibitors—a cornerstone of hypertension and heart failure treatment—have been shown to be less effective at lowering blood pressure in Black patients compared to white patients. This difference is not a matter of compliance or access; it reflects genuine physiological differences in the renin-angiotensin system that regulates blood pressure.

In recognition of this, the FDA approved BiDil in 2005 specifically for the treatment of heart failure in self-identified Black patients—the first drug approved for use in a specific racial group. While the approval generated significant ethical debate about the use of race as a biological category in medicine, it also drew attention to the reality that racial and ethnic background can carry clinically relevant pharmacological information.

Calcium channel blockers and thiazide diuretics, by contrast, have demonstrated stronger antihypertensive effects in Black patients. Yet prescribing patterns do not always reflect these evidence-based distinctions, partly because the evidence itself is underappreciated in clinical training.

Pain Management

The opioid codeine is metabolized into morphine by the CYP2D6 enzyme. Genetic variants that affect CYP2D6 activity differ in frequency across populations. Ultra-rapid metabolizers—who convert codeine to morphine at an accelerated rate—face an elevated risk of toxicity from standard doses. Conversely, poor metabolizers may receive virtually no pain relief. These variants are distributed unevenly across ethnic populations, yet dosing guidelines rarely account for this variability in routine clinical practice.

Research published in peer-reviewed journals has also documented that patients of color are, on average, undertreated for pain compared to white patients—a disparity driven in part by persistent racial bias among clinicians but compounded by a lack of population-specific dosing data.

Psychiatric Medications

Studies have found that Black patients prescribed antipsychotic medications are more likely to receive higher doses than white patients with equivalent diagnoses—a pattern that increases exposure to serious side effects, including tardive dyskinesia. Separately, research has identified that Asian patients may require lower doses of certain antipsychotics and mood stabilizers to achieve therapeutic effects, a difference linked in part to pharmacokinetic variation.

The consequences of ignoring these differences range from inadequate symptom control to preventable adverse drug reactions.

The Research Pipeline Problem

The FDA has required the reporting of clinical trial data by sex since 1993, and has encouraged, though not consistently required, the reporting of data by race and ethnicity. Despite incremental improvements, a 2020 analysis found that clinical trial populations continue to underrepresent Black, Hispanic, Asian, and Indigenous participants relative to their share of the U.S. population—and that subgroup analyses by race are frequently absent from published results even when diverse participants are enrolled.

This creates a compounding problem. Physicians cannot prescribe with population-specific nuance when that nuance has not been generated. Pharmacists cannot flag potential dosing concerns that are not reflected in the drug's labeling. And patients cannot advocate for themselves without the vocabulary to name the gap.

What Patients of Color Can Do

The most actionable step available to patients today is to raise the question of pharmacogenomics explicitly with their prescribing physician. Pharmacogenomic testing—which analyzes an individual's genetic variants to predict drug metabolism—is increasingly available and, in some clinical contexts, covered by insurance. For patients on medications with known CYP450 interactions, this testing can provide genuinely individualized guidance.

Beyond genetic testing, patients can ask their physicians directly whether the medications being prescribed have been studied in populations that reflect their ancestry, and whether any dose adjustments are warranted based on that research. These are not unreasonable questions. They are, in fact, questions that reflect the current frontier of precision medicine.

Patients should also be aware that reporting unusual responses to medications—whether insufficient efficacy or unexpected side effects—is valuable clinical data. The FDA's MedWatch program accepts voluntary adverse event reports from patients, and such reports contribute to the ongoing refinement of drug safety profiles across diverse populations.

Moving Toward Equitable Pharmacology

The solution to this systemic gap lies upstream, in the design of clinical trials and the regulatory expectations placed on drug manufacturers. Advocacy organizations, academic researchers, and some legislators are pushing for stronger mandates requiring that new drug applications include meaningful data on diverse populations before approval is granted.

For the patients who exist in the present, however, the most effective tool remains informed engagement with their own healthcare. Knowing that dosing recommendations are not universally derived—and that genetic ancestry is a legitimate variable in drug response—is the first step toward ensuring that your treatment plan reflects you, not a statistical average that was never designed to include you.