Epinephrine Vasoconstriction Effect Time in the Scalp Differs According to Injection Site and Concentration

In a study from 2016 involving 25 healthy volunteers, it was found that the duration of scalp vasoconstriction caused by epinephrine injections increased with the concentration of the drug. Four different concentrations were tested: 1:400,000, 1:200,000, 1:100,000, and 1:50,000. The longest vasoconstriction times were observed with the highest concentration, particularly at the frontotemporal junction of the frontal hairline (Point B) compared to the supraorbital artery path (Point A), with a statistically significant difference at the 1:50,000 concentration. The study suggests that the vasoconstriction effect of epinephrine in scalp surgeries, such as hair transplantation, is influenced by both the concentration of epinephrine and the specific injection site. The authors recommend careful consideration of these factors to optimize surgical outcomes, suggesting the use of the smallest effective dose of epinephrine, dividing the surgical field to match the drug's duration, and monitoring peripheral oxygen saturation during injection.