A PROSPECTIVE EVALUATION OF BENZOCAINE-ASSOCIATED METHEMOGLOBINEMIA IN HUMAN-BEINGS

Study objective: This study determined the frequency and severity of b enzocaine-associated methemoglobinemia in routine clinical use. Design : Prospective, crossover, convenience study. Setting: Gastroenterology clinic at a US Army medical center functioning as a community hospita l and tertiary referral center. Participants: Healthy adult volunteers and patient volunteers undergoing an upper gastrointestinal endoscopi c procedure. Interventions: Baseline methemoglobin levels were measure d. Subjects then received a 2-second spray of benzocaine to the oropha rynx. Venous blood for methemoglobin analysis was collected 20, 40, an d 60 minutes after benzocaine dosing and analyzed using a co-oximeter. Results: A statistically significant (P<.05) increase in methemoglobi n level between baseline (0.8+/-0.2%) and 20-, 40-, and 60-minute meas urements (0.9+/-0.2%) was identified using one-way analysis of varianc e followed by Fisher's protected least-squares difference. Conclusion: A 2-second spray of 20% benzocaine applied to the oropharynx of human beings induces a statistically significant, but clinically insignific ant, increase in methemoglobin levels.