In an early 1988 examine revealed within the Journal of the Autonomic Nervous System, researchers injected atropine into the muscular tissues of 20 wholesome male adults. Eight of the individuals had brown eyes, one other eight had blue eyes, and 4 people had hazel eyes. Atropine is a drug used to deal with signs of bradycardia, or a slowed coronary heart charge of fewer than 50 beats per minute accompanied by unstable affected person very important indicators, in response to 2023 up to date analysis revealed in StatPearls.
Utilizing two totally different units to manage the drug, the researchers measured participant pupil dilation and coronary heart charge inside the first hour and a half of the intervention. The analysis findings confirmed that males with brown eyes skilled quicker coronary heart charge acceleration than these with hazel or blue eyes. The researchers theorized that melanin, akin to that discovered inside the iris, could modify the physique’s response to atropine. This was strengthened in 2022 analysis revealed within the Journal of Managed Launch, through which the researchers level out that sure medication — akin to atropine, timolol, and levofloxacin — bind to melanin, thereby heightening the drug’s focus and remaining within the physique for longer durations of time.