Clinical trials are crucial for medical advancement, as they help determine whether a new treatment, device, or procedure works and is safe for the general population. However, people of color are often underrepresented in many drug trials.
“For decades, drugs have been largely tested on white, non-Hispanic men,” says Geeta Yadav, MD, a board-certified dermatologist and founder of FACET Dermatology. “There’s evidence that women and patients of color respond quite differently to medication. Failure to test drugs on a diverse patient population can lead to many issues, including a lack of accessibility to effective medical intervention, compounded health disparities between patient populations, and a lack of trust in the medical community.”
A research review published in Human Genomics revealed that darker skin tones can affect certain medications’ safety and effectiveness, indicating a need for better representation of people of color in clinical drug trials.
The review, led by researchers Simon Groen, PhD, and Sophie Zaaijer, found that melanin—the natural substance that produces hair, eye, and skin pigmentation—can interact with some medications, which could alter the medication’s effect on the body.
There are two types of melanin: pheomelanin and eumelanin. Eumelanin has been found to play a larger role in drug interactions. Its unique chemical makeup gives it high binding affinity (strong binding between molecules) for various substances.
10 Drugs that Affect Darker Skin Differently
Some examples of drugs that have a high binding affinity with eumelanin include:
- Acetaminophen
- Ampicillin
- Antidepressants
- Chlorpromazine
- Ciprofloxacin
- Clozapine
- Cocaine
- Haloperidol
- Nicotine
- Penicillin G
Although the skin is the body’s largest organ, there’s little research on the potential drug interactions with eumelanin. One study showed that clozapine (an antipsychotic used to treat schizophrenia) was found in lower concentrations in the plasma of people with sub-Saharan African ancestry compared to those with European ancestry.
Another study revealed that varying levels of eumelanin can influence a person’s nicotine use and dependence. This ultimately could impact people with darker skin tones, as nicotine patches are popularly used as a form of smoking cessation.
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With little understanding of how certain drugs can interact with darker skin tones, it can be difficult for healthcare providers to know how effective a treatment will be for their patients.
“Currently, we don’t have a way to predict which patients will respond better to which medications,” Dr. Yadav says. “Ideally, we’d be able to personalize treatments, and part of that may be based on the person’s genetic profile, which might make them more responsive to a particular treatment versus another.”
Skin Conditions that Affect Darker Skin More
People with darker skin are more likely to experience certain skin conditions, including:
Post-inflammatory hyperpigmentation (PIH)
A common type of pigmentation problem that can occur after skin injuries, such as cuts, scrapes, or burns. PIH can also occur with acne or eczema.
Melasma
A common pigment disorder that causes brown patches on the face, most often on the cheeks, forehead, and upper lip. Hormones from pregnancy and birth control pills may play a role in causing melasma.
Pseudofolliculitis barbae (PFB)
Also known as barber’s itch, this is a chronic inflammation of the beard area caused by shaving. It’s more common in men with darker skin types and curly hair.
Keloids
Raised, shiny scars that are often uncomfortable and can grow larger than the original wound. Black skin is particularly prone to keloid formation.
Other skin conditions that can affect people with darker skin include: Hidradenitis suppurativa (HS), Rosacea, Seborrheic dermatitis, and Skin cancer.
Eczema on Darker Skin
Why Eczema in Darker Skin Is an Issue
Also known as dermatitis, this skin condition is characterized by an itchy, red rash that comes on gradually and lasts a long time. It can be triggered by such things as stress, extreme changes in temperature, dry skin, pet or plant allergies, or irritations caused by skin care or cosmetic ingredients.
When eczema occurs as the result of an inherited tendency, it is known as atopic dermatitis.
Eczema is believed to occur twice as frequently in children with dark skin. One study found its incidence is higher in Mexican-American teens than either whites or blacks. Other research found a greater incidence in Chinese and Vietnamese babies, compared with white babies.
When eczema occurs in those with dark complexions, it presents a two-fold problem:
- It is often misdiagnosed, leading to long periods of no treatment or the wrong treatment.
- When not treated early on, it can increase the risk of pigmentation problems.
Treatment for eczema consists of identifying and avoiding products that irritate skin. Use of moisturizer can help a lot, along with steroid creams. Sometimes, ultraviolet light therapy is effective.
It is essential to seek help as soon as possible for any red, itchy rash. Doing so will help avoid pigmentation problems.
What’s Being Done for Darker Skin in Clinical Trials?
As of now, very few guidelines address the issue surrounding skin pigmentation and drug interactions. The U.S. Food and Drug Administration (FDA) recently issued draft guidance, “Diversity Action Plans to Improve Enrollment of Participants from Underrepresented Populations in Clinical Studies,” to increase diversity in clinical drug trials.
The FDA’s recently enacted Food and Drug Omnibus Reform Act (FDORA) requires medical product sponsors of phase 3 clinical trials or other significant clinical drug studies to submit a Diversity Action Plan designed to increase the enrollment of participants from underrepresented or marginalized populations.
While the government is making some efforts to make clinical trials more inclusive, the review’s researchers propose the following as the next steps for addressing skin pigmentation drug interactions:
- Pharmaceutical companies should use 3D-pigmented human skin models to examine how new drugs interact with different skin tones.
- Clinical trial participants of color should ask clinical investigators if the drugs have been tested to ensure they’re safe for their skin tones.
“This study offers a compelling argument for expanding the focus on pigmentation in drug development, which could ultimately lead to more personalized and effective treatments for all patients,” Dr. Yadav says.
For those interested in participating in a research study, BDO’s Clinical Trial Resource Center and ClinicalTrials.gov help connect people with researchers who are recruiting eligible participants across the United States.
