A comparison of the ventilatory, cardiovascular and metabolic effects of salbutamol, aminophylline and vasoactive intestinal peptide in normal subjects.

Intravenous infusion of placebo for 30 min followed by either salbutamol 10 micrograms min-1, aminophylline 0.2 mg kg-1 min-1 or vasoactive intestinal peptide (VIP) 6 pmol kg-1 min-1 for 30 min was performed in a single blind fashion in six normal volunteers. Both salbutamol and aminophylline increased minute ventilation, (P less than 0.05) the mean increase being 26% and 19% respectively. Aminophylline also increased the ventilatory response to carbon dioxide by 47% (P less than 0.05) when measured by hyperoxic rebreathing, whereas salbutamol and VIP were without significant effect. All three drugs caused a tachycardia, mean increase in the pulse being 16, 8 and 2 beats min-1 for salbutamol, aminophylline and VIP respectively, and aminophylline also increased both systolic and diastolic blood pressure, mean arterial pressure increasing by 14 mmHg. VIP caused haemoconcentration and salbutamol the expected changes in plasma biochemistry. Plasma catecholamines increased slightly during drug infusion, although this effect is unlikely to be important.