Does promethazine (Atosil) influence the human's early acoustically evoked potentials in the same way as the late potential N1?

In a former investigation the effect of promethazine (Atosil) on the late acoustically evoked potential component N1 was examined. Now the cochlear and the brain-stem potentials were registered by the earlobe-vertex pick-up with i.m. application of 0.8 mg/kg (body weight) promethazine. There was no influence of promethazine either on the compound action potential (NAP) or on the brain-stem potentials (Pot. II-V), but sedation improves significantly the signal-to-noise ratio, therefore we sedate all patients when registering the five early acoustically evoked potentials.