OBJECTIVE AND SUBJECTIVE TREMOR RESPONSES TO ORAL BETA-2 AGENTS ON 1ST EXPOSURE - A COMPARISON OF METAPROTERENOL AND TERBUTALINE

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Abstract
Objective and subjective postural tremor responses at 60 and 120 min after drug treatment were studied in 24 veterans with chronic obstructive pulmonary diseases who received 5 mg terbutaline, 20 mg metaproterenol or a placebo in random order. Subjects were fasting and had not taken theophylline for 15-24 h or any oral sympathomimetics for 2 wk. The mean tremor response to terbutaline and metaproterenol was equal at 60 min, but the 120-min response to metaproterenol was less. When the 60- and 120-min responses were averaged, tremor response to terbutaline was significantly greater than that to metaproterenol in a 5:4 ratio. Subjective awareness was also greater. These results are consistent with the difference in bronchodilatory potency of the 2 preparations. That the drug producing the greater tremor could usually be identified by the patient, even at low tremor intensities, is consistent with the hypothesis that perception of tremor is a function of relative rather than absolute increase over basal tremor, unless the tremor becomes physically disabling. In general, the individual tremor response was proportional to the extent by which a patient''s basal tremor exceeded the minimal basal tremor for the group as a whole. Apparently, the postural tremor derives from .beta.-sensitive and .beta.-insensitive cardioballistic and skeletal muscle forces. Variability in tremor response resides principally at the peripheral skeletal .beta.-receptor and its control system.