Ten healthy volunteers, aged 25 to 58 years (mean 37 years), two African Americans and eight Caucasian Americans, applied the standard 1.0 mL dose (2 mg of lorazepam, 25 mg of diphenhydramine, and 2 mg of haloperidol in a pluronic lecithin organogel), rubbed on the volar surface of the wrists by the subject.
Blood samples were obtained at 0, 30, 60, 90, 120, 180, and 240 minutes. Plasma concentrations were analyzed by liquid chromatography-tandem mass spectrometry using deuterated internal standards for each drug.
No lorazepam or haloperidol was detected in any sample from any of the 10 volunteers down to a level of 0.05 ng/mL. Diphenhydramine was found in multiple plasma samples at concentrations >0.05 ng/mL in three patients, with the highest concentration of 0.30 ng/mL in one person at 240 minutes. Overall, five of 10 patients exhibited detectable diphenhydramine in one or more samples, supporting limited absorption. No subject noted any side effects.
As commonly used, none of the lorazepam, haloperidol, or diphenhydramine in ABH gel is absorbed in sufficient quantities to be effective in the treatment of nausea and vomiting. Diphenhydramine is erratically absorbed at subtherapeutic levels. The efficacy of ABH gel should be confirmed in聽randomized trials before its use is recommended.