A prospective evaluation of benzocaine-associated methemoglobinemia in human beings.
OBJECTIVE
This study determined the frequency and severity of benzocaine-associated methemoglobinemia in routine clinical use.


METHODS
Prospective, crossover, convenience study.


METHODS
Gastroenterology clinic at a US Army medical center functioning as a community hospital and tertiary referral center.


METHODS
Healthy adult volunteers and patient volunteers undergoing an upper gastrointestinal endoscopic procedure.


METHODS
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.


RESULTS
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.


CONCLUSIONS
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.
Guertler
A T
AT
Department of Emergency Medicine, Madigan Army Medical Center, Tacoma, Washington.
Pearce
W A
WA
D000328:Adult; D000336:Aerosols; D000368:Aged; D000369:Aged, 80 and over; D000704:Analysis of Variance; D001566:Benzocaine / Q000008:administration & dosage / Q000009:adverse effects*; D005260:Female; D006801:Humans; D016018:Least-Squares Analysis; D008297:Male; D008706:Methemoglobin / Q000032:analysis; D008708:Methemoglobinemia / Q000097:blood / Q000139:chemically induced*; D008875:Middle Aged; D009960:Oropharynx; D011446:Prospective Studies; D013997:Time Factors
D000336:Aerosols; D008706:Methemoglobin; D001566:Benzocaine