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Abstract
Since all the patients reportedly had prior experience with the phenothiazines (presumably including prochlorperazine), it seems likely that they would be aware of the feelings of lethargy that usually accompany the use of prochlorperazine. Since patients were told that they would receive either a conventional antiemetic or a marihuana-like substance, it seems to us that many of the patients could have been aware of which substance they had received. [...]given that 23 of 58 subjects (40 per cent) presumed refractory to prochlorperazine responded to it in this study, we must wonder about the placebo-like effects of the patients' knowledge that they were being studied and about the effect of the highly suggestive instruction that the purpose of the study was to "control nausea and vomiting." To the Editor: Since the earlier publication of Sallan et al. (in 1975),1 we have also studied the antiemetic effect of THC, with monitoring of blood levels, in a double-blind crossover trial against a placebo2 in 12 patients with a Hodgkin's or non-Hodgkin's lymphoma treated with the MOPP (mechlorethamine, vincristine, procarbazine, prednisone) regimen.3 We agree with Sallan et al. that THC has a pronounced antiemetic effect. Since our main comparisons were based on the same person's receiving both antiemetics, the age bias is not present in our study.