Vasoactive intestinal peptide as a bronchodilator in severe asthma.

In two studies vasoactive intestinal peptide (VIP) was administered intravenously to two groups of eight in-patient volunteers recovering from severe acute asthma. VIP (6 pmol/kg/min) infusion caused significant (p less than 0.01) increase in peak expiratory flow rate (PEFR) of 26 +/- 9 (SEM) l/min after 30 minutes infusion compared with a bronchodilation of 39 +/- 19 l/min seen with salbutamol (5 mcg/min). Following pretreatment with nebulized ipratropium bromide, VIP infusion caused a significant (p less than 0.02) bronchodilation of 25 l/min. VIP is a bronchodilator in severe asthma, although its effects are less than conventional medication. Reflex mechanisms are unlikely to explain the bronchodilatory effect of intravenous VIP.