Comparison of the protective effect of orciprenaline with an orciprenaline-oxymetazoline combination on experimental bronchospasm in guinea pigs.

alpha-Adrenergic agonists with pulmonary vasoconstrictor activity could potentiate or prolong the bronchodilator action of a locally administered beta-adrenergic agonist by decreasing transpulmonary absorption of the compound. Results of studies using the alpha-agonist oxymetazoline and the beta-agonist orciprenaline (metaproterenol) showed that the combination of oxymetazoline [0.3 microgram] with orciprenaline (3 micrograms) offered no potency advantage and only a small duration advantage over orciprenaline alone in antagonizing a histamine-induced bronchospasm in guinea pigs. Higher doses (10 and 30 micrograms) of oxymetazoline caused bronchoconstriction when given alone and inhibited the bronchodilator action of orciprenaline. The relevance of these findings for human asthmatics hyperresponsive to the bronchoconstrictor action of alpha-agonists is discussed.