A prospective evaluation of benzocaine-associated methemoglobinemia in human beings.

Abstract

This study determined the frequency and severity of benzocaine-associated methemoglobinemia in routine clinical use. Prospective, crossover, convenience study. Gastroenterology clinic at a US Army medical center functioning as a community hospital and tertiary referral center. Healthy adult volunteers and patient volunteers undergoing an upper gastrointestinal endoscopic procedure. Baseline methemoglobin levels were measured. Subjects then received a 2-second spray of benzocaine to the oropharynx. Venous blood for methemoglobin analysis was collected 20, 40, and 60 minutes after benzocaine dosing and analyzed using a co-oximeter. A statistically significant (P < .05) increase in methemoglobin level between baseline (0.8 +/- 0.2%) and 20-, 40-, and 60-minute measurements (0.9 +/- 0.2%) was identified using one-way analysis of variance followed by Fisher's protected least-squares difference. A 2-second spray of 20% benzocaine applied to the oropharynx of human beings induces a statistically significant, but clinically insignificant, increase in methemoglobin levels.