Premedication of Children With Promethazine, Propiomazine, and Mepazine: Comparison of Oral and Intramuscular Routes

¹ Department of Anesthesiology, Mount Sinai Hospital, University Circle, Cleveland, Ohio 44106.

Three phenothiazine drugs were administered in varying dosages and combinations to children as preanesthetic medication. The items evaluated included hypnotic depth, antisalivary effect, respiratory depression, and incidence of emesis during emergence and in the early postoperative period.

Mepazine, 0.67 mg/lb, plus 0.006 mg/lb scopolamine intramuscularly in a small series was not impressive from the standpoint of hypnotic effect and was excessively painful on injection.

Promethazine,0.25 mg/lb, combined with 0.5 mg/lb meperidine and 0.006 mg/lb scopolamine intramuscularly gave a satisfactory frequency of moderate to deep hypnotic depth when induction was performed more than 45 minutes after the premedication was given. This combination gave satisfactory results in all other parameters evaluated. Increasing the promethiazine dosage in this combination to 0.5 mg/lb produced no apparent difference in results. Although these parenteral promethazine combinations produced clinically satisfactory results, significant advantages over a "standard" secobarbitalscopolamine combination were not evident; therefore they are not recommended for routine use.

A combination of 0.67 mg/lb promethazine, 0.67 mg/lb meperidine, and 0.025 mg/lb scopolamine was administered orally. Hypnotic depth in this series was significantly decreased as compared with the parenteral combinations. At least 45 minutes was required between administration and peak hypnotic and antisalivary effects. Increasing the oral promethazine dosage to 1.0 mg/lb produced no improvement in either hypnotic depth or antisalivary effect. Promethazine is not recommended for oral premedication, since it provides no apparent advantage over several other oral preparations shown to be more effective in producing drowsiness.

Propiomazine was similarly evaluated, in a parenteral combination containing 0.33 mg/lb propiomazine, 0.5 mg/lb meperidine, and 0.006 mg/lb scopolamine. Hypnotic depth was comparable to secobarbital-scopolamine premedication, but antisalivary action was more rapid in onset. Incidence of respiratory depression during ether anesthesia was higher than in the promethazine groups. Other parameters varied within clinically acceptable limits. Decreasing the meperidine dosage in this combination from 0.5 to 0.33 mg/lb reduced the incidence of respiratory depression during ether anesthesia. In all other respects, the results were comparable to the other parenteral combinations in this study. It was demonstrated that the peak effect of this combination did not occur until 60 minutes after administration, contrary to previously reported claims of unusually rapid onset of hypnotic action of this drug. As with promethazine, advantages of this combination were not sufficient to recommend its substitution for other "standard" methods.

Propiomazine, 0.5 mg/lb, was then combined orally with 0.67 mg/lb meperidine and 0.025 mg/lb scopolamine. Hypnotic effect tended to be less profound in this series than with parenteral propiomazine. Antisalivary action was as good as with intramuscular scopolamimine and better than with promethazine, chloral hydrate, or secobarbital given orally with the same dose of scopolamine. Thus, a significant antisalivary action of oral propiomazine was demonstrated, but a significant increase in emesis on emergence as well as a significant increase in the volume of gastric contents were also found. This oral conibination was concluded to be clinically adequate, with much better antisalivary effect and somewhat more profound hypnotic effect than 0.67 or 1.0 mg/lb promethazine orally. Increasing the oral propiomazine dosage to 0.75 mg/lb did not enhance the hypnotic effect or produce other significant changes. Despite the favorable antisalivary action of oral propiomazine, its inability to equal several other oral agents in hypnotic potency and the increased incidence of postoperative vomiting associated with its use make it undesirable as a routine method of oral premedication for children.

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