THE EFFECT OF TRIFLUOPERAZINE ON BRONCHIAL RESPONSIVENESS IN ASTHMA

1. The protective effects of oral trifluoperazine (TFP) (7mg) against standardized methacholine and histamine inhalation tests (MIT and HIT) were examined 2 and 22 h post‐treatment in eight stable asthmatics using a randomized double‐blind protocol. 2. A preliminary study tested whether a preceding MIT influenced the result of a subsequent HIT. 3. The mean baseline forced expiratory volumes in 1 s (FEV₁) were similar prior to placebo and TFP. The mean FEV₁ values 2 h after ingestion of placebo or TFP were not different from the baseline values. 4. TFP did not alter bronchial responsiveness to inhaled methacholine or histamine 2 h postingestion, but at 22 h the PC₂₀ methacholine was greater than placebo, while PC₂₀ histamine did not change. This change in methacholine responsiveness was not clinically significant. 5. There was a correlation between geometric mean provocative concentration of histamine to cause 20% fall in FEV (PC₂₀H) for HIT performed in isolation ('separate day') and for HIT performed after MIT (‘same day’). 6. The effect of inhaled TFP (10 mg/ml, nebulized for 5 min) was examined single‐blind and placebo‐controlled in a separate group of six stable asthmatics. 7. Inhaled TFP had a bronchoconstrictor effect in all six asthmatics. The mean fall in FEV₁ was 36.4% after inhaled TFP and 2.1% after saline. 8. In the asthmatics studied, ingested TFP exhibited a weak anticholinergic effect 22 h pest‐treatment, but a brisk spontaneously self reverting bronchoconstrictor response was invariably seen when TFP was inhaled.