THE EFFECTS OF POTENT ANALGESICS UPON VESTIBULAR FUNCTION

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Abstract
The occurrence of dizziness, nausea and vomiting is increased in the ambulant patient who receives meperidine, methadone or morphine. The methods employed were the cold micro-caloric test and galvanic stimulation of the mastoid area. In the former, nystagmus is produced by ice water injd. into the external auditory canal and the time in sec. for its onset and duration recorded with a stop-watch. This test depends upon the integrity of the peripheral end-organ in the labyrinth. The latter method consists in recording the milliamperage required to tilt a subject who is holding the moistened cathode in one hand while the examiner applies the moistened anode to the contra-lateral mastoid area. It depends upon the integrity of the vestibular nerve tract and associated brain centers. 25 trials were made consisting of 3 base-line detns. and the following drugs admd. parenterally (codeine 60 mg., meperidine 50 mg., morphine 10 mg., methadone 10 mg., pantopon 20 mg. and acetylsalicylic acid 0.6 g.[long dash]this last orally). Tests were repeated at 20 min. intervals. Morphine, meperidine, methadone and pantopon increased labyrinthine sensitivity, while codeine exerted an opposite action. Acetylsalicylic acid produced no changes in vestibular function. The increased labyrinthine responsiveness produced by morphine and meperidine was blocked by the prior admn. of dimenhydrinate 100 mg. orally. In studies with meperidine utilizing only the cold micro-caloric test the resultant increased vestibular sensitivity was of greater magnitude in the upright than in the supine position.