In a call for change, some researchers are urging the U.S. Food and Drug Administration (FDA) to consider an often-overlooked factor in drug trials: the color of a patient’s skin.

An article published in Human Genomics on Oct. 9 suggests that melanin, the skin pigment responsible for skin tone, can bind to drug compounds and may significantly influence how medications interact with the body.

This revelation could have implications for millions of patients and may change the approach to clinical trials, drug safety, and dosing.

Skin Pigments Prolong Drug Effects

The authors found that skin pigments can bind to some drug compounds, warranting widespread investigation into how they affect drug efficacy.

There are two types of melanin in the body: eumelanin, which is more common in darker skin tones, and pheomelanin, which is more common in lighter skin tones.

Eumelanin has a higher affinity for certain compounds, including antimalarial drugs such as chloroquine, antipsychotics such as clozapine, and antibiotics such as ciprofloxacin.

These drugs can be stored in pigmented tissues such as the skin and eyes for longer periods, potentially leading to extended drug effects or increased toxicity.

The implications of melanin “for drug safety and dosing have been largely overlooked, raising alarming questions about the efficacy of standard dosing” given the wide variation in human skin tones, article co-author Simon Groen, an assistant professor of evolutionary system biology at the University of California–Riverside, wrote in a statement.

Most evidence of adverse effects related to melanin levels comes from studies on ocular toxicity, Sophie Zaaijer, co-author and a consultant and researcher specializing in preclinical research and development (R&D) and clinical trials, told The Epoch Times.

“Cells in the retina [in the eyes] contain the highest concentrations of melanin that can bind to certain drugs, and the most extreme adverse effects for some of these drugs have been identified,” Zaaijer said. “While skin has a lower concentration of melanin per cell or surface measure compared to eyes, the cumulative sum of melanin stored in the skin is high due to the skin being the largest organ of our body.”

Aside from skin pigment, people’s ability to metabolize drugs can also affect their reactions to certain medications.

Skin Pigment Affects Nicotine Absorption

The researchers also found evidence suggesting nicotine’s affinity for skin pigments could affect smoking habits in people with different skin tones, raising questions about the efficacy of nicotine patches for smoking cessation.

In people with darker skin, nicotine may accumulate in the skin and hair, which could lead to its prolonged retention in the body.

This extended retention may affect nicotine dependence, as individuals with higher melanin levels may experience prolonged withdrawal symptoms.

“Are we inadvertently shortchanging smokers with darker skin tones if they turn to these patches in their attempts to quit?” Groen asked in the statement.

Currently, the effects of melanin on nicotine absorption seem contradictory.

“Links between variation in skin pigmentation and tobacco use were indeed found in a study with individuals of African-American ancestry, with a smaller study finding no significant correlation,” Zaaijer and Groen wrote in their paper.

One study found that black males had lower odds of achieving smoking abstinence, while the same effect was not seen in black women. Another study of more than 40 black people, however, did not find any evidence of a correlation between melanin and nicotine dependence.

Zaaijer said the issue of nicotine patches and skin color is being studied at a deeper level at the University of California–San Francisco. If higher levels of melanin correlate with longer nicotine retention, she suggests nicotine patches could be tailored to skin color or alternative solutions could be developed for people with darker skin.

Antipsychotic Drug Concentrations Differ

The researchers cited the antipsychotic drug clozapine as an example of a drug whose efficacy is affected by skin color. Clozapine is prescribed for people with schizophrenia who don’t respond to other drugs.

An analysis of clozapine’s pharmacokinetics showed that individuals of black African descent retained lower concentrations of the drug compared to individuals of European descent. Genetic studies have shown that African Americans may have a higher prevalence for metabolizing enzymes that rapidly break down drugs, leading to lower drug concentrations in the body.

Coincidentally, clozapine also binds with melanin in the skin. The authors said skin pigmentation interactions may have also contributed to slower drug release.

“The main message that our manuscript aims to capture is: Potential effects of melanin skin pigments on drug safety and efficacy should be tested,” Groen told The Epoch Times.

Similar to how a drug affects people with darker skin tones differently, pesticides and other chemicals could also have different effects, Groen said.

“Some fertilizers and pesticides also have affinity for melanin. This can cause differences in exposure to chemicals between people with varying skin tones.”

According to the two researchers, current FDA guidelines for toxicity testing inadequately address the impact of skin pigmentation on drug interactions.

“Current early-stage drug development practices still primarily focus on drug testing in white populations of Northern European descent,” Zaaijer wrote in the statement.

“Our best hope is to ensure that all people, regardless of their ancestral background, have equal chances of receiving the highest level of drug efficacy and safety,” she told The Epoch Times via email. “This seems to be something that we as a biomedical community can do: an achievable goal, since it is within our own control.”