Bufuralol is a non-specific β-adrenergic blocker.

Beta adrenergic agonists are medications relaxing muscles of the airways, which widens the airways and leads to easier breathing. Beta adrenergic agonists are a class of sympathomimetic agents that act upon the beta adrenoceptors.

In vitro: Bufuralol was identified as a non-cardioselective β-adrenoceptor antagonist which possessed partial agonist activity at the β-adrenoceptor. Bufuralol also showed membrane-stabilizing properties [1].

In vivo: Previous pharmacological studies in several species of animals showed that bufuralol exhibited non-selective β-adrenoceptor blocking properties similar to those of propranolol with comparable potency. Such effects were exerted on the β-adrenoceptor stimulant actions of injected amines and of sympathetic nerve stimulation. However, unlike propranolol, bufuralol possessed some instrinsic sympathomimetic activity as demonstrated by tachycardia in reserpinized rats [2].

Clinical trial: Clinical observations were made in eight subjects who exercised before and after the oral administration of placebo, bufuralol and propranolol. Results showed that the exercise heart rate remained constant after placebo. Bufuralol at 7.5 mg and propranolol at 40 mg could reduce exercise heart rate but bufuralol at 15, 30, 60 and 120 mg and propranolol at 160 mg were still active at 24 h. The lowest exercise heart rate occurred at 2 h after treatments. Bufuralol at 60 and 120 mg could produce similar reduction in exercise tachycardia as propranolol at 40 mg but less than propranolol at 160 mg [2].

References:
[1] Fothergill GA, Francis RJ, Hamilton TC, Osbond JM, Parkes MW.  Bufuralol, a new beta-adrenoceptor blocking agent. Experientia. 1975 Nov 15;31(11):1322-3.
[2] Pringle, T. H.,Francis, R.J.,East, P.B., et al. Pharmacodynamic and pharmacokinetic studies on bufuralol in man. Br.J.Clin.Pharmac. 22, 527-534 (1986).