Effects of H1-receptor blockade with terfenadine in nocturnal asthma

1. In a single-blind placebo controlled study we have measured peak flow (PEFR) at 04.00 h and 16.00 h in eight asthmatics 6 h after placebo or terfenadine 120 mg, to determine if diurnal variation in histamine mediated effects contribute to nocturnal bronchoconstriction in asthma. 2. On placebo there was a significant diurnal variation in mean PEFR of 41 l min-1 (P less than 0.05). Terfenadine improved 04.00 h baseline mean PEFR from 242 to 278 l min-1 (P less than 0.05) but a 38 l min-1 diurnal variation in mean PEFR persisted (P less than 0.05). 3. We conclude that H1-receptor blockade with terfenadine may produce modest nocturnal bronchodilatation but does not influence the diurnal variation in PEFR in asthma suggesting that H1-receptor mediated effects are not important in the pathogenesis of nocturnal asthma.