Rapid Mucosal Absorption of Topical Lidocaine During Bronchoscopy in the Presence of Oral Candidiasis: Discussion
This case is remarkable in that lidocaine solution and jelly applied to the oropharynx and bronchial tree were rapidly and extensively absorbed attaining a peak plasma concentration of 7.1 μg/ml within 0.67 hour of the start of drug administration (Fig 1). Furthermore, for four hours after the procedure, the plasma levels remained greater than 1.5 μg/ ml, which is within the antiarrhythmic “therapeutic” range of 1.5 to 5.5 μml. These plasma concentrations are greater than most literature reports of 1 to 4 μg/ml during bronchoscopy and higher than what we observed in a study of 19 bronchoscopy patients receiving a total average lidocaine dosage of 1,240 mg administered in a regimen similar to the regimen described here. In that study, the average peak plasma concentration was 2.6 ± 1.0 μg/ml.
The conclusions to be drawn from these data are limited by the fact that it was impractical to quantitate the amount of drug which was suctioned back through the bronchoscope and therefore was unavailable for absorption. In this case report, however, the fact that high plasma lidocaine concentrations were attained very rapidly is suggestive of rapid drug absorption through the extensive mucosal surface area lining the oropharynx and bronchial tree.
In addition to enhanced rate of absorption, the patient exhibited a greater systemic availability of lidocaine. Comparing area under the plasma lidocaine concentration curve (AUC, time 0 to 4 h) as a measure of the extent of drug absorption, the patients AUC was 13.8 μg/ml X h, about double that of the study population (6.0 ±2.3 jtgfrnlxh). This greater systemic availability could not be attributed to decreased hepatic oxidation of lidocaine since the patients plasma elimination half-life of 1.5 hour was normal. Despite a peak concentration of 7.1 μg/ml and sustained levels above 1.5 μg/ml, the patient did not manifest any undesired drug effects.